4 preformulation

Lecture Outline
• The first unit of lectures in Pharmaceutics IV will be based on the
following:
• Introduction to pharmaceutical dosage form processing:
 General introduction to manufacturing process system
 Formulation Assessment
 Analytical Method Development
 Formulation Development
 Good Manufacturing and Compounding Practices
 Drug Product Stability

CONTENTS
• Introduction
• Organoleptic properties
• Purity
• Particle size, shape and surface area
• Solubilisation, Surfactants and its importance
• Temperature, pH, co-solvency, solid dispersion, β-
cyclodextrin drug-dispersion system
• Preformulation stability studies
• A consideration of physico-chemical characteristics of
new drug molecules with respect to different dosage
forms
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Manufacturing Process
• Manufacturing is the production of merchandise for use or
sale using labour and machines, tools, chemical and biological
processing, or formulation.
• The term may refer to a range of human activity,
from handicraft to high tech, but is most commonly applied
to industrial production, in which raw materials are
transformed into finished goods on a large scale.
• Manufacturing processes are the steps through which raw
materials are transformed into a final product.
• The manufacturing process begins with the creation of the
materials from which the design is made.
• These materials are then modified through manufacturing
processes to become the required part.
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• Manufacturing takes turns under all types of economic systems.
• In a free market economy, manufacturing is usually directed toward
the mass production of products for sale to consumers at a profit.
• In a collectivist economy, manufacturing is more frequently directed by the
state to supply a centrally planned economy.
• In mixed market economies, manufacturing occurs under some degree of
government regulation.
• Modern manufacturing includes all intermediate processes required for the
production and integration of a product's components.
• Manufacturing processes can include treating (such as heat treating or
coating), machining, or reshaping the material.
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• The manufacturing process also includes tests and
checks for quality assurance during or after the
manufacturing, and planning the production process
prior to manufacturing.
• Such finished goods may be used for manufacturing
other, more complex products, such
as medicines, household appliances or automobiles,
or sold to wholesalers, who in turn sell them
to retailers, who then sell them to end
users and consumers.
• This first learning phase is called as preformulation.
04/05/2012 KLE College of Pharmacy, Nipani. 6

Preformulation
• Preformulation is branch of Pharmaceutical science that
utilizes biopharmaceutical principles in the determination
of physicochemical properties of the drug substance.
• Prior to the development of any dosage form new drug ,
it is essential that certain fundamental physical &
chemical properties of drug powder are determined .
• This information may dictate many of subsequent event
& approaches in formulation development.
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INTRODUCTION
DEFINITION:-
Investigation of physico-chemical properties
of the new drug compound that could affect
drug performance and development of an
efficacious dosage form”.
Preformulation commences when a newly
synthesized drug shows a sufficient
pharmacologic promise in animal model to
warrant evaluation in man.
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Introduction
• The preformulation is the first step in the rational
development of a dosage form of a drug substance
alone and when combined with excipients.
• Objective :
To generate useful information to the formulator
to design an optimum drug delivery system.
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• Before embarking on a formal programme of
preformulation, scientist must consider the following
:
1. Available physicochemical data (including
chemical structure, different salt available).
2. Anticipated dose.
3. Supply situation and development schedule.
4. Availability of stability – indicating assay.
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Introduction

GOALS OF PREFORMULATION
• To establish the necessary physicochemical
parameters of new drug substances.
• To determine kinetic rate profile.
• To establish physical characteristics.
• To establish compatibility with common
excipients.
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Preliminary Evaluation
a) Compound identity.
b) Formula and molecular weight.
c) Structure.
d) Therapeutic indications:
- Probable human dose.
- Desired dosage form(s)
- Bioavailability model
- Competitive products
Contd…
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e) Potential hazards
f) Initial bulk lots:
- Lot number
- Crystallization solvent(s)
- Particle size range
- Melting point
- % volatiles
g) Analytical methods:
- HPLC assay
- TLC assay
- UV/ Visible spectroscopy
Contd…
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Preliminary Evaluation

ORGANOLEPTIC PROPERTIES
COLOR ODOUR TASTE
OFF-WHITE PUNGENT ACIDIC
CREAM-YELLOW SULFUROUS BITTER
SHINY FRUITY SWEET
AROMATIC TASTELESS
ODOURLESS TASTELESS
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• Color is generally a function of a drug’s inherent
chemical structure relating to a certain level of
unsaturation.
• Color intensity relates to the extent of conjugated
unsaturation as well as the presence of
chromophores.
• Some compound may appear to have color although
structurally saturated.
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COLOR

• The substance may exhibit an inherent odor
characteristic of major functional groups present.
• Odor greatly affects the flavor of a preparation or
food stuff.
Taste:-
• If taste is considered as unpalatable, consideration is
to be given to the use of a less soluble chemical form
of the drug.
• The odour and taste may be suppressed by using
appropriate flavors and excipients or by coating the
final product.
04/05/2012 16
Odour

PURITY
• Designed to estimate the levels of all known &
significant impurities & contaminates in the drug
substance under evaluation.
• Study performed in an analytical research &
development group.
• It is another parameter which allows for comparison
with subsequent batches.
• Occasionally, an impurity can affect stability.
e.g.
- Metal contamination
- Appearance
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• The techniques used for characterizing the purity of a
drug are the same as those used for other purpose in a
preformulation study.
• Thin layer chromatography is a wide ranging
applicability & is an excellent tool for characterizing
the purity.
• HPLC, paper chromatography & gas chromatography
are also useful.
• More quantitative information can be obtained by
using quantitative differential scanning colorimetry.
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PURITY

PARTICLE SIZE
• Particle size is characterized using these
terms :
i. Very coarse (#8)
ii. Coarse (#20)
iii. Moderately coarse (#40)
iv. Fine (#60)
v. Very fine (#80)
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• Particle size can influence variety of
important factors :
- Dissolution rate
- Suspendability
- Uniform distribution
- Penetrability
- Lack of grittiness
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PARTICLE SIZE

Methods to Determine Particle Size
• Sieving
• Microscopy
• Sedimentation rate method
• Light energy diffraction
• Laser holography
• Cascade impaction
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1. Sieving method :
• Range : 50 – 150 µm
• Simple, inexpensive
• If powder is not dry, the apertures get clogged.
2. Microscopy :
• Range : 0.2 – 100 µm
• Particle size can be determined by the use of
calibrated grid background.
• Most direct method.
• Slow & tedious method.
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3. Sedimentation method :
• Range : 1 - 200 µm
• Andreasen pipette is used.
• Particle size is calculated by stoke’s law :
dst =
Where,
h = distance of fall in time, t
no = viscosity of the medium
ρs = density of the particles
ρ0 = density of the dispersion medium
g = acceleration due to gravity
18 η0 h
(ρs -ρ0) gt
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4. Light energy diffraction :
• Range : 0.5 – 500 µm
• Particle size is determined by the reduction in light
reaching the sensor as the particle, dispersed in a liquid
or gas, passes through the sensing zone.
• Quick & fast.
5. Laser holography :
• Range : 1.4 – 100 µm
• A pulsed laser is fired through an aerosolized particle
spray & photographed in three dimensional with
holographic camera, allowing the particles to be
individually imaged & sized.
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6. Cascade impaction :
• The principle that a particle driven by an
airstream will hit a surface in its path,
provide that its inertia is sufficient to
overcome the drug force that tends to keep in
it in airstream.
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POWDER FLOW PROPERTIES
 Powder flow properties can be affected by change in particle
size, shape & density.
 The flow properties depends upon following-
1. Force of friction.
2. Cohesion between one particle to another.
 Fine particle posses poor flow by filling void spaces between
larger particles causing packing & densification of particles..
 By using glident we can alter the flow properties.
e.g. Starch, Talc.
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Determination Of Powder Flow Properties
 By determining Angle Of
Repose.
 A greater angle of repose
indicate poor flow.
 It should be less than 30°.
& can be determined by
following equation.
tan θ = h/r.
where, θ = angle of repose.
h=height of pile.
r= radius.
Angle Of
Repose
( In degree)
Type Of Flow
<25 Excellent
25-30 Good
30-40 Passable
>40 Very poor
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 Measurement of free flowing powder by
compressibility.
 Also known as Carr's index.
CARR’S INDEX(%) =(TAPPED DENSITY – POURED DENSITY) X 100
TAPPED DENSITY
 It is simple, fast & popular method of predicting powder
flow characteristics.
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Carr’s Index Type of flow
5-15 Excellent
12-16 Good
18-21 Fair To Passable
23-35 Poor
33-38 Very Poor
>40 Extremely Poor
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PARTICLE SHAPE
Cont…04/05/2012 30

• Particle shape will influence the surface area, flow of
particles, packing & compaction properties of the
particles.
• A sphere has minimum surface area per unit volume.
• Therefore, these properties can be compared for
spheres & asymmetric particles, in order to decide the
shape.
• The following expression can be obtained:
Property Sphere particle
surface area πds
2 αs x dp
2
volume (1/6)πds
3 αv x dp
3
Cont…
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PARTICLE SHAPE
31

• Therefore,
surface area = πds
2 = αs x dp
2
Volume = (1/6)πds
3 = αv x dp
3
• Solving for αs & αv by equating the appropriate properties
provides:
αs =
πds
2 & αv = πds
3
• When particle shape is spherical, the ds = dp
• Thus, αs = π = 3.124 & αv = π/6 = 0.524
• Therefore, Shape factor = αs = 3.124 = 6
αv 0.524
Cont…
dp2 6 dp3
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PARTICLE SHAPE

SURFACE AREA
• Particle size & surface area are inversely
related to each other.
• Smaller the drug particle, greater the surface
area.
Specific surface is defined as the surface area
per unit weight (Sw) or unit volume (Sv) of the
material.
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 Estimation of Sv :
Sv = Surface area of the particles
Volume of particles
= n αs d2
n αv d3
= αs
αv d
• According to shape factor,
αs =
αv
• So, Sv = 6 / d.
6
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SURFACE AREA

 Estimation of Sw:
Sw = Surface area = Surface area
Weight density x volume
= Sv
ρ
= 6
ρ . d
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SURFACE AREA

Methods for determining
surface area
1. Adsorption method :
• Particles with a large specific surface are good
adsorbents for the adsorption of gases & of solutes
from solution.
• The volume of nitrogen gas, Vm, in cm3 that 1 g of the
powder can adsorb when the monolayer is complete is
more accurately given by using the BET equation,
however, which can be written as:
P = 1 + (b-1) . P
V(P0 – P) Vmb Vmb P0
Cont….04/05/2012 36

• Where,
V = Volume of gas in cm3 adsorbed per gram of powder
at pressure P.
P = Pressure of the adsorbate, in mmHg.
Po= Saturation vapor pressure (monolayer)
Vm= Amount of vapor adsorbed per unit mass adsorbent,
when the surface is covered with monomolecular
layer
b = Constant that express the difference between the
heat of adsorption & heat of liquefaction of the
adsorbate (nitrogen).
Cont….
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Methods for determining
surface area

P
V( P0 – P)
P/P004/05/2012 38
Quantasorb QS – 16 instrument

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Air permeability method :

HOWEVER SIZE REDUCTION
IS NOT REQUIRED IN FOLLOWING CASES
• WHEN DRUG IS UNSTABLE.
• DEGRADE IN SOLUTION FORM.
• PRODUCE UNDESIRABLE EFFECTS.
• WHEN SUSTAINED EFFECT IS DESIRED.
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SOLUBILIZATION
“ Solubilization is defined as the spontaneous
passage of poorly water soluble solute
molecules into an aqueous solution of a soap
or detergent in which a thermodynamically
stable solution is formed ”.
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 It is the process by which apparent solubility of
an otherwise sparingly soluble substance is increased
by the presence of surfactant micelles .
 MICELLES: -
 The mechanism involves the property of
surface active agents to form colloidal aggregates
known as micelles .
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SOLUBILIZATION

 When surfactants are added to the liquid at low
concentration they tend to orient at the air-liquid
interface .
 On further addition of surfactant the interface
becomes completely occupied and excess molecules
are forced into the bulk of liquid.
 At very high concentration surfactant molecules in
the bulk of liquid begin to form micelles and this
concentration is know as CRITICAL MICELLE
CONCENTRATION {CMC}
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SOLUBILIZATION

 Solubilization is thought to occur by virtue of the
solute dissolving in or being adsorbed onto the
micelle.
 Thus the ability of surfactant solution to
dissolved or solubilize water insoluble materials
starts at the CMC and increase with increase in the
concentration of micelles.
 Solubilization of any material in any solvent
depends on proper selection of solubilising agents.
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SOLUBILIZATION

 The process of solubilization involves the breaking
of inter-ionic or intermolecular bonds in the solute,
the separation of the molecules of the solvent to
provide space in the solvent for the solute,
interaction between the solvent and the solute
molecule or ion.
Step 1: Holes opens in the solvent
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Step2: Molecules of the solid breaks away from the
bulk
Step 3: The free solid molecule is intergraded into
the hole in the solvent
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 The amount of substance that passes into
solution in order to establish equilibrium at
constant temperature and pressure to
produce a saturated solution.
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 If solubility is <1mg/ml indicates need for salt
formation to improve solubility.
 If solubility is <1mg/ml in pH= 1 to 7,
preformulation study should be initiated.
 Solubility should ideally be measured at two
temperatures: 4°C and 37°C.
 4°C to ensure Physical stability.
 37°C to support Biopharmaceutical evaluation.
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Description Parts of solvent required
for one part of solute
Very soluble < 1
Freely soluble 1 - 10
Soluble 10 - 30
Sparingly soluble 30 - 100
Slightly soluble 100 - 1000
Very slightly
soluble
1000 - 10,000
Insoluble > 10,000
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SOLUBILITY ANALYSIS
 Preformulation solubility studies focus on drug
solvent system that could occur during the delivery of
drug candidate.
 For e.g. A drug for oral administration should be
examined for solubility in media having isotonic
chloride ion concentration and acidic pH.
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 Analytic method that are particularly useful
for solubility measurement include HPLC, UV
spectroscopy, Fluorescence spectroscopy and
Gas chromatography.
 Reverse phase HPLC offer accurate and
efficient mean of collecting solubility data of
drug.
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SOLUBILITY ANALYSIS

 Ionization constant (pKa)
Can be calculated by Henderson Hasselbach
equation-
For acidic drugs….pH= pKa+ log [ionized drug]
[unionized drug]
For basic drugs….pH= pKa+ log[unionized drug]
[ionized drug]
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 pH Solubility Profile
 The solubility of acidic or basic drug will show
difference in solubility with changes in pH.
 pH solubility profile of a drug can be established
by running the equilibrium solubility experiment
within pH range of 3-4.
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 Partition Coefficient
 It is the ratio of unionized drug distributed
between organic and aqueous phase at equilibrium.
P o/w = ( C oil / C water )equilibrium
04/05/2012 54

 Effect Of Temperature
 The heat of solution Hs, represents the heat
released or absorbed when a mole of solute is
dissolved in large quantity of solvent.
 Endothermic reaction
 Exothermic reaction
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Determination of solubility
 The following points should be considered
 The solvent & solute must be pure.
 A saturated solution must be obtained before any
solution is removed for analysis.
 The method of separating a sample of saturated
solution from undissolved solute must be
satisfactory.
 The method of analyzing solution must be reliable
 Temperature must be adequately controlled .
04/05/2012 56

Solubility Determination Method
 Solubility is normally depends on temperature,
so temperature is recorded in each solubility
measurement.
 Plot of solubility against temperature is
commonly used for solubility determination.
 Two methods are available for determination
are as follow.
I. Analytical method
II. Synthetic method
04/05/2012 57

Analytical method
 Temperature of equilibrium is fixed and
concentration of the solute in the saturated solution
is determined at equilibrium by a suitable
analytical procedure.
 In other words a saturated solution in the
presence of an excess of the undissolved solute is
prepared at an accurately known temperature.
This situation can be achieved by suitable contact
b/w solute and solvent.
04/05/2012 58

 In this method a weighed amount of solute is
placed in the vessel.
 While agitating the system at constant temperature
known amount of solvent is added gradually until
the solubility limit is reached.
 At equilibrium, temperature and content of the
system is recorded.
 This method is carried out at micro scale level by
examining the small amount of the system under
hot stage microscope.
04/05/2012 59
Synthetic method

 Addition of co-solvent
 pH change method
 Reduction of particle size
 Temperature change method
 Hydotrophy
 Addition of Surfactant
 Dielectrical Constant
 Complexation
04/05/2012 60
General Method of Increasing
the Solubility

• Weak Electrolyte :- Phenobarbitone
• Non polar :- Nitro Cellulose
 These are poorly soluble in given solvent.
 For such poorly soluble materials, to enhance
their solubility, the water miscible solvents are used
in which the drug has good solubility.
 This process of improving solubility is known as
co-solvency and the solvent used is known as co-
solvents.
04/05/2012 61
Addition Of Co-Solvent

e.g. Phenobarbitone is insoluble in water. A clear
solution is obtained by dissolving in mixture of
Alcohol, Glycerin, Propylene glycol.
e.g. Of Cosolvents:-
PG, glycerin, sorbitol, PEG, Glyceryl formal,
glycofurol, ethyl carbamate, ethyl lactate and
dimethyl acetamide.
04/05/2012 62
Addition Of Co-Solvent

pH change Method
 Weak base:- Alkaloids, Local Anaesthesia
 Weak acid:- Sulphonamides, Barbiturates
 In aqueous medium they dissociate poorly and
undissociated portion is insoluble.
e.g. Benzoic acid, Phenobarbitone
 So, solubility of the undissociated portion is
improved by pH control.
For weak acidic drug:- increase pH, solubility is
increase.
 For weak base drug:- decrease pH, increase
solubility.
04/05/2012 63

 Reduction in Particle size improve solubility of
drug.
 Basically reduction in particle size increase contact
surface area of the particle, there by ultimately it
increase rate of solubility of drug.
Reduction Of Particle size
04/05/2012 64

 In endothermic reaction by increasing temperature
solubilityisincrease.
 In exothermic reaction by increasing temperature
solubility is decrease.
e.g. Methyl Cellulose when mixed with water and
temperature is raised, it becomes insoluble. To
dissolve it cold water is added.
04/05/2012 65
Temperature Change Method

The term Hydotrophy has been used to designate the
increase in solubility in water of various substances
due to the presences of large amount of additives.
e.g. Solubilization of Benzoic acid with Sodium
benzoate.
04/05/2012 66
Hydotrophy

 Surfactants are molecules with well defined polar
and non-polar region that allow them to aggregate in
solution to form micelles. Non polar drugs can
partition into micelles and be solubilized.
e.g. Surfactant based solution of Taxol, that is
solubilized in 50% solution of Cremophor.
04/05/2012 67
Addition of Surfactant

Dielectrical Constant is the effect that substances
has, when it acts as a solvent on the case with which it
separates oppositely charged atoms.
e.g. DEC of Water- 80
Kerosene- 2
Glycerine- 48
Benzene- 2.2
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Dielectrical Constant

Complexation
 For the Complexation occur both drug and ligand
molecule should be able to donate or accept
electrons.
 The solubility of compound is the sum of solubility
of the compound and its complex.
e.g. HgI2 (Mercuric Iodide) is sparingly soluble in
water. Its solubility in water is increased by forming
complex with KI.
HgI2 +2KI K2HgI4 (water soluble)
04/05/2012 69

Applications of solubilization
 Drugs with limited aqueous solubility can be
solubilized. These include oil-soluble vitamins,
steroid hormones and antimicrobial agents etc.
 Solubilization of orally administered drugs results
in an improved appearance and improves
unpleasant taste.
 Both oil-soluble and water-soluble compounds can
be combined in a single phase system as in case of
multivitamin preparations.
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 Solubilization may lead to enhanced absorption
and increased biological activity.
 Improves the intestinal absorption of vitamin A.
 Drug absorption from ointment bases and
suppositories also increased.
 Liquid preparations with small quantity of
preservative can be prepared by solubilization.
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 Aqueous concentrates of volatile oils can be
prepared by solubilization.
 Example: soaps used for solubilising phenolic
compounds for use as disinfectants- Lysol, Roxenol
etc.
 Barbiturates, anticoagulant, alkloidal drugs are
dissolved with polysorbate by solubilization.
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SURFACTANT
 Surfactants:-
are wetting agents that lower the surface
tension of a liquid, allowing easier spreading,
and lower the interfacial tension between two
liquids.
 Classification
Some commonly encountered surfactants of
each type include:
1. Ionic 2. Non ionic
 Cationic
 Anionic
 Zwitterionic
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IONIC
 Cationic Surfactants:-
 Quaternary ammonium salts are more preferred
because they are less affected by pH.
e.g. Cetyl Trimethyl Ammonium Bromide (CTAB)
Hexadecyl Trimethyl Ammonium Bromide, and other
Alkyltrimethyl Ammonium Salts, Cetylpyridinium
Chloride (cpc)
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Anionic Surfactants:-
 They are the most commonly used surfactants,
containing Carboxylate, Sulfonate, Sulfate ions.
e.g. Sodium Dodecyl Sulphate (SDS), Ammonium
Lauryl Sulphate and other alkyl sulfate salts, Sodium
Laureth Sulphate, also known as Sodium Lauryl
Ether Sulphate (SLES).
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IONIC

 Zwitterionic:-
 When a single surfactant molecule exhibit both
anionic and cationic dissociations it is called
amphoteric or Zwitterionic.
The anion include carboxylates and phosphate
group and the cation include quaternary
ammonium group.
e.g. Dodecly Betamine
Dodecly Dimethylamine Oxide
04/05/2012 76
IONIC

NONIONIC
 These are most widely used because they are
free from non compatability, stability and
potential toxicity and classified as water soluble
and water insoluble non ionic surfactants.
e.g. Long chain fatty acids, fatty alcohols
 Water solubility of these agents is further
increased by addition of polyoxyethylene groups
through ether linkage with one of the alcohol
group.
e.g. spans
04/05/2012 77

HLB SCALE
 Griffin in 1947 developed the system of the
hydrophilic-lipophilic balance [ HLB ] of surfactant.
 The higher the HLB of the an agent, the more
hydrophilic it is.
 Tween, polyoxyethylene derivative of the spans are
hydrophilic and have high HLB value (9.6-16.7)
 The lower the HLB of the agent, the more lipophilic
it is.
 The sorbitan ester are lipophilic and have low HLB
value (1.8-8.6)
04/05/2012 78

HLB SCALE
Most antifoaming agents
W/O Emulsifying agents
Wetting and Spreading agents
O/W Emulsifying agents
Detergents and Solubilizing agents
0
3
6
9
12
15
18
04/05/2012 79

• The HLB of non ionic surfactant whose only
hydrophilic portion is polyoxyethylene is calculated
using the formula
• HLB = E/5
Where, E = Percentage weight of ethylene oxide
04/05/2012 80
HLB SCALE

Importance Of Surfactant
 Surfactants play an important role in many
practical applications and products, including:
• Detergents
• Fabric Softener
• Emulsifier
• Paints
• Adhesive
• Inks
• Soil remediation
• Wetting
04/05/2012 81

• Ski Wax
• Snowboard Wax
• Foaming
• Defoaming
• Laxatives
• Agrochemical formulations
Herbicides
Insecticides
• Quantum dot coating
• Biocides (Sanitizers)
• Hair Conditioners (after shampoo)
• Spermicide (Nonoxynol 9)
04/05/2012 82
Importance Of Surfactant

Temperature, pH, Cosolvancy, Solid
dispersion
04/05/2012 83

Effect of Temperature
• The solubility of a solute in a solvent is dependent on
temperature, nature of solute and nature of solvent.
• Heat of solution represents the heat released or
absorbed when a mole of solute is dissolved in a large
quantity of solvent.
• Most of the substances are endothermic, absorbing
heat in the process of dissolution.
04/05/2012 84

• For this substances, an increase in temperature results
in an increase in solubility.
• Exothermic substances give off heat in the process of
dissolution. The solubility of such substances would
decrease with increase in temperature.
• Care should be taken as heat may destroy a drug or
cause other changes in the solution.
e.g. On excess heating the sucrose solution it can get
converted in to the invert sugar.
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• Depending on the type of reactions weather it is
exothermic or endothermic heat is either released or
absorbed.
e.g. Mixture of chloroform and acetone. The heat
produced by the solute-solvent interaction is so much
greater than the heat necessary to separate the
molecules of acetone and chloroform, which can be
detected as a rise in temperature of the liquid.
04/05/2012 86

• Applications:
• Pharmaceutical solutions must be administered
at or near room temperature. So, it is more
important factor for product storage than the
formulation.
• To increase the solubility of sparingly
soluble solute.
• To increase the stability by reducing the
moisture content.
04/05/2012 87

Effect of pH
• Weak electrolytes undergo ionization and are more
soluble when in ionized form. The degree of ionization
depends on dissociation constant (pKa) and the pH of the
medium.
• Solubility is a function of pH, that is related to its pKa
which gives ratio of ionized and unionized forms of the
substance.
This can be shown as:
pH = pKa + log [ A-
]
[ HA ]
04/05/2012 88

• If the substance is brought outside its pKa, i.e. the pH
value where half the substance is ionized and half is
not, than solubility will be changed because we are
introducing new intermolecular forces, mainly ionic
attraction.
• e.g. –COOH has pKa value at pH around 4. If pH is
increased then –COOH is converted into –COO-
.
This may interact with the H+
of water.
04/05/2012 89
Effect of pH

• The effect of pH on solubility for weak electrolytes
can be described by:
pHp = pKa + log S –S0
S0
• Where,
pHp = pH below which the drug precipitates from
solution as the undissociated acid.
S = total solubility.
S0 = molar solubility of the undissociated acid.
04/05/2012 90
Effect of pH

• It is to be ensured that pH change for one
single compound should not affect the other
requirements of product.
• e.g. the chemical stability of drug may depend
on pH, and this pH of optimum stability should
not coincide with the pH of other ingredients
specially colors, preservatives and flavors.
04/05/2012 91
Effect of pH

Cosolvancy
• To enhance the solubility of poorly soluble
materials, the water miscible solvents are used in
which the drug has good solubility. This process
of improving solubility is known as co-solvency.
• Solvents used to increase the solubility are
known as co-solvents.
04/05/2012 92

• The mechanism for solubility enhancement by
co-solvency is not clearly understood. But it is
proposed that, solubility is increased may be
by reducing the interfacial tension between the
solvent and hydrophobic solutes and
decreasing dielectric constant of solvent.
04/05/2012 93
Cosolvancy

• The commonly used and acceptable co-solvents in
formulation of aqueous liquids for oral solutions are
Ethanol, Sorbitol, Glycerin, Several members of PEG
series.
• For parenteral products, Dimethylacetamide is widely
used. But in case of oral liquids its application is
limited, because of its objectionable odour and taste.
04/05/2012 94
Cosolvancy

• Some characteristics of co-solvent, which are used in
preparation:
1. It must be non-toxic. Non-irritating.
2. It should be able to solubilize the drug in
given solvent.
3. It should be able to cross the membrane.
• Apart from increasing solubility, they are also used to
improve the solubility of volatile constituents used to
impart a desirable flavour and odour to the product.
04/05/2012 95
Cosolvancy

Solid – Dispersion System
• Definition :
Solid dispersion is defined as dispersion of one or
more active ingredients in an inert carrier or matrix at
solid state prepared by the melting, solvent or melting
solvent method.
04/05/2012 96

Classification
(Based on Fast Release Mechanism)
• Simple Eutectic Mixtures
• Solid Solutions
• Glass Solutions and Glass Suspensions
• Amorphous precipitation of drug in crystalline
carrier
• Compounds or Complex formation between drug
and carrier
• Any combination among the above
04/05/2012 97

A. Eutectic Mixtures
• When two or more substances are mixed
together they liquefy due to the lowering of
melting point than their individual melting
point. Such substances are called as eutectic
substances.
e.g. paracetamol-urea, griseofulvin-urea
04/05/2012 98

• Simple binary phase
diagram showing eutectic
point E.
• The eutectic composition at
point E of substance A and
B represents the melting
point.
• TA and TB are melting
point of pure A and pure B.
04/05/2012 99

• The following factors may contribute to faster
dissolution rate of drug dispersed in the eutectic
mixtures:-
1. Increase in drug solubility.
2. Solubilization effect by the carrier which
completely dissolves in a short time in diffusion
layer surrounding drug particles.
3. Absence of aggregation and agglomeration
between fine crystallites of pure hydrophobic
drug.
04/05/2012 100

4. Excellent wettability and dispersibility
of a drug as the encircling soluble carrier
readily dissolves and causes water to
contact as wet drug particles.
5. Crystallization of drug in a metastable
form after solidification from fused solution,
which has high solubility.
04/05/2012 101

• Eutectics are easy to prepare and economical
with no solvents involved. The method
however cannot be applied to:
- Drugs which fail to crystallize from
mixed melt.
- Thermolabile drugs.
- Carriers such as succinic acid that
decompose at melting point.
04/05/2012 102

B. Solid Solutions
• It is made up of a solid solute dissolved in a solid
solvent. It is often called a “mixed crystal” because
the two components crystallize together in a
homogenous phase system.
• It is prepared by fusion method.
• A solid solution of poorly soluble drug in a rapidly
soluble carrier achieves a faster dissolution because
particle size of drug is reduced to molecular size.
04/05/2012 103

• According to extent of miscibility :
1. Continuous (iso-morphous, unlimited,
complete) solid solution.
2. Discontinuous (limited, restricted,
incomplete) solid solution.
• According to crystalline structure of solid
solutions :
1. Substitutional solid solutions.
2. Interstitial solid solutions.
Classification
04/05/2012 104

a) Continuous Solid Solutions :-
 The two components are miscible or soluble at
solid state in all proportions.
 No established solutions of this kind has been
shown to exhibit fast release dissolution properties.
 The faster dissolution rate would be obtained if the
drug is present as a minor compartment.
b) Discontinuous Solid Solutions :-
 There is only limited solubility of a solute in a solid
solvent in this group of solid solutions.
04/05/2012 105
Classification

C. Glass Solutions and Glass
Suspensions
• A glass solution is a homogenous, glassy system in
which a solute is usually obtained by abrupt
quenching of the melt.
• Many compounds have been shown to be able to
form glasses readily upon cooling from liquid state.
• These compounds include sucrose, glucose, ethanol
and 3- methyl hexane.
04/05/2012 106

• It is presumably due to their strong hydrogen bonding
which may prevent their crystallization.
• Polymers possessing linear, flexible chains can freeze
into a glass state to transparency and brittleness.
• The strength of chemical binding in a glass solution is
much less compared to that in a solid solution.
• Hence, dissolution rate of drugs in the glass solution
is faster than in solid solution.
• e.g. Glass solution of citric acid
04/05/2012 107
C. Glass Solutions and Glass
Suspensions

D. Amorphous Precipitation
of Drug in Crystalline Carrier
• Instead of forming a simple eutectic mixture in which
both drug and the carrier crystallize simultaneously
from a solvent method of preparation, the drug may
also precipitate out in an amorphous form in
crystalline carrier.
• It has faster dissolution and absorption rates than
crystalline form.
• e.g. Amorphous novobicin has 10 fold higher
solubility than its crystalline form.
04/05/2012 108

• Dissolution and absorption of a drug can occur from a
complex or a compound formed between the drug and
an inert soluble carrier.
• Complexation also implies that dissolution could be
retarded as observed with PEG 4000 - phenobarbital.
• However, the formation of a soluble complex with a
low association constant results in increased rates of
dissolution and absorption.
E. Compound or Complex
Formations
04/05/2012 109

F. Combinations and
Miscellaneous Mechanisms
• A solid dispersion entirely belongs to any five groups
discussed so far, but it can also be made up of
combinations of different groups.
• These combinations increase the dissolution and
absorption rate.
• The griseofulvin dispersed at high concentrations in
PEG may exist as individual molecules and as micro-
crystalline particles.
04/05/2012 110

Methods of Preparations
• Melting Method
• Solvent Method
• Melting - Solvent Method
• Hot Melt Extrusion Technique
04/05/2012 111

1. Melting Method or
Fusion Method
• The physical mixture of a drug and water soluble
carrier is heated until it melts.
• The melt is then cooled and solidified rapidly in an
ice bath with vigorous stirring .
• The final solid mass is crushed, pulverized and
sieved.
• To facilitate faster solidification, the homogenous
melt is poured in the form of a thin layer onto
stainless steel plate and cooled by flowing air or
water on the opposite side of the plate.
04/05/2012 112

• Advantages :
• Simplicity of method.
• Supersaturation of a solute or a drug in a system can
often be obtained by quenching the melt rapidly from
high temperature.
• Disadvantage :
• Some drugs or carriers may decompose or evaporate
during fusion process at high temperatures .
e.g. succinic acid used as a carrier for griseofulvin is
quite volatile and may also partially decompose by
dehydration near its melting point.
04/05/2012 113
1. Melting Method or Fusion Method

2. Solvent Method
• They are prepared by dissolving a physical
mixture of two solid components in a common
solvent, followed by evaporation of the
solvent.
• The method is used to prepare solid
dispersions of griseofulvin-
polyvinylpyrrolidone, sulphathiazole - pvp.
04/05/2012 114

• Advantage :
- Thermal decomposition of drugs or carriers can be
prevented because of low temperature required for
the evaporation of organic solvents.
• Disadvantages :
- High cost of preparation.
- Difficulty in completely removing the solvent.
- Difficulty in producing crystal forms.
04/05/2012 115
2. Solvent Method

3. Melting Solvent Method
• It is prepared by first dissolving the drug in a
suitable solvent and then incorporating this solution
in a melt of PEG without removing the solvent.
• Advantages :
Same as above two methods
• Disadvantage :
From practical stand point, it is only limited to
drugs with a low therapeutic dose, e.g. below 50mg.
04/05/2012 116

4. Hot Melt Extrusion Method
• In this method, a blend of active ingredients,
polymeric carrier and other processing aids like
plasticizers and antioxidants is heated and softened.
• This softened material is called as extrudate.
• When the extrudate is cooled at room temperature,
the polymeric thermal binder solidifies and bonds the
excipients together to form a matrix.
04/05/2012 117

• Advantages :
- There are no concerns with solvent handling or
recovery after processing
- It is simple and continuous process for
preparation of tablets and granulations.
- The process is faster and there were fewer steps
than the wet granulation method.
- Can be used for formulating sustained
release granules.
e.g. Diltiazem granules.
04/05/2012 118
4. Hot Melt Extrusion Method

Methods of Determination
of Solid Dispersion Systems
• Thermal analysis
a) Cooling curve method
b) Thaw-melt method
c) Thermoscopic method
d) Differential thermal analysis (DTA)
e) Zone Melting Method
04/05/2012 119

• X-Ray diffraction Method
• Microscopic method
• Spectroscopic method
• Thin layer chromatography
• Solubility determinations
04/05/2012 120
Methods of Determination
of Solid Dispersion Systems

A. Thermal Analysis
• It is used to study the physico-chemical
interactions of two or more components.
• Principle : Change in thermal energy as a
function of temperature.
a) Cooling curve method :
- The physical mixtures of various
compositions are heated until a
homogenous melt is obtained.
- The temperature of the mixture is then
recorded as function of time.
04/05/2012 121

b) Thaw-melt method :
- Here a sample of solidified mixture in a
capillary melting point tube is heated
gradually till the thaw point.
- The thaw point is referred to as crossing
solidus line.
- It is useful in differentiating between a
simple eutectic system and a limited
solution.
04/05/2012 122
A. Thermal Analysis

c) Thermoscopic method :
- Polarized microscopy is used with hot
stage to study phase diagrams of binary
systems.
- The physical mixture is gradually
heated on a slide until it completely
liquefies.
- After cooling, the mixture is heated at rate
of 4 degree per minute.
- The thaw and melting points are
determined by visual observations.
04/05/2012 123
A. Thermal Analysis

d) Differential thermal analysis (DTA) :
- An effective thermal method for studying
phase equilibria of either pure compound or
mixture.
- Different effects, associated with physical
or chemical changes are automatically
recorded as function of time or temperature as
the substance is heated in uniform rate.
- In addition; evaporation, sublimation,
polymorphic transition, desolvation can
be detected.
04/05/2012 124
A. Thermal Analysis

e) Zone Melting Method :
- It is primarily used for ultra
purification of metal and inorganic and
organic metal.
04/05/2012 125
A. Thermal Analysis

B. X-Ray Diffraction Method
• In this method the intensity of x-ray diffraction or
reflection from a sample is measured as a function of
diffraction angles.
• Counter and film methods detect diffraction intensity.
• Counter method provides better resolution of
diffraction and relative intensity which can be easily
compared.
• This method is used to characterize physico-chemical
properties of Griseofulvin dispersed in PEG 4000 and
6000.
04/05/2012 126

C. Microscopic Method
• It has been used to study polymorphism and
morphology of solid dispersion.
• The fine particles of crystallization in glass
PVP can be easily detected by polarizing
microscope.
• The resolution of electron microscope was
used to study dispersed particle size of iopanic
acid in PVP.
04/05/2012 127

D. Spectroscopic Method
• In the UV study, the spectra of pure drug and
the dispersed drug are scanned.
• e.g. The spectrum of the dispersed beta –
carotene resembles that beta–carotene is
dissolved in organic solvents but do not
indicate the molecular dispersion of drug in
polymer.
04/05/2012 128

E. Thin Layer Chromatography
• TLC characteristics of pure and dispersed
drugs are studied to test whether the drugs are
decomposed by process.
• A single spot with same ‘Rf ’value is expected
for both the pure and processed samples in thin
layer plate.
04/05/2012 129

F. Solubility determinations
• Results from aqueous solubility studies of drug
in various concentrations of carrier would
indicate interactions between drug and carrier.
• Such studies indicated weak or insignificant
interactions between griseofulvin and PEG
6000.
• Increased rate of dissolution due to solubility
of the drug by carrier can be predicted by this
method.
04/05/2012 130

Pharmaceutical Applications
• To obtain a homogenous distribution of small
amount of drugs at solid state.
• To stabilize unstable drugs.
• To dispense liquid or gaseous compounds.
• To formulate a faster release priming dose in a
sustained release dosage form.
• To formulate sustained release dosage or
prolonged release regimens of soluble drugs by
using poorly soluble or insoluble carriers.
04/05/2012 131

β-cyclodextrin drug dispersion system,
techniques for studies of crystals,
polymorphism
04/05/2012 132

β-cyclodextrin drug dispersion system
• The poorly dissolution of relatively insoluble drug
has for long been a problem in the formulation of
oral dosage form.
• This limits the aspect such as
 Absorption &
 Bioavailability
04/05/2012 133

• Several approach have been followed in improving
the solubility of drug, one of them being
complexation using cyclodextrin.
• Cyclodextrin is cyclic structure oligomers of glucose
which are obtained from the starch digests of the
bacteria Bacillus macerans.
04/05/2012 134

• The most abundant cyclodextrins available are
a-cyclodextrin - 6 glucose units
b-cyclodextrin - 7 glucose units
g-cyclodextrin - 8 glucose units
04/05/2012 135

Chemistry of b-cyclodextrin
• Cyclodextrine molecule have cylindrical shape with
central axial cavity and resembles with shape of
truncated cone.
• The interior cavity is hydrophobic and the outside of
the molecule is hydrophilic.
04/05/2012 136

Characteristics of β-cyclodextrin
• Glucose unit – 07
• Molecular wt. – 1135
• Solubility – 1.85g/100ml
• Cavity diameter – 6.4 Ao
• Diameter of outer periphery –
15.4 Ao
• Approx. vol. of cavity –
262 (Ao
)3
04/05/2012 137

Method of preparation of b-cyclodextrin
complex
• Physical mixture method
• Kneading method
• Co-evaporation method
• Solid dispersion method
• Spray drying method
• Neutralization method
04/05/2012 138

Physical mixture method
• Here the drug and b-cyclodextrin (1:2) are mixed
physically with spatula & then the pulverized powder
is passed through 100#.
• Eg. Diclofinac sodium
04/05/2012 139

Kneading method
• Here the b-cyclodextrin is dissolved in small vol. of
water-methanol solution(6:4).
• To the above solution required drug is added in small
amount.
• The slurry is then kneaded for 45 min. & dried at
45o
c.
• The dried mass is pulverized and sieved through
100#.
• Eg. Nimesulide , Omeprazole
04/05/2012 140

Co-evaporation method
• In this method, aq. solution of b-cyclodextrin is added
to an alcoholic solution of drug.
• The resulting mix. is stirred for 1 hr. & evaporated at
45o
c until it is dried.
• The dried mass is pulverized and sieved through
100#.
• Eg. Steroids & Diclofenac sodium
04/05/2012 141

Solid dispersion method
• Here the drug & molar qty. of b-cyclodextrin is
dissolved in methanol.
• The solution is then evaporated in vacuum at 40o
c
with rotatory evaporator.
• The powder is stored under vacuum in dessicator for
3 days & analysed.
• Eg. Rifampicin
04/05/2012 142

Spray drying method
• In this, the drug & double molar of β-cyclodextrin are
dissolved in methanol.
• The solution was then spray dried under foll.
conditions –
Feed rate – 10 ml/min
Inlet temp. - 95o
c
Outlet temp. - 65o
c
Press. – 5 bar
Drying air – 35 m3
04/05/2012 143

• The powder is then collected & stored under vacuum
in dessicator for 3 days & analysed.
• Eg. Naproxene
04/05/2012 144
Spray drying method

Neutralization method
• Here the drug & b-cyclodextrin are dissolved in 0.1N
HCl & then 0.1N NaOH is added to precipitate the
complex at pH-7.5.
• The ppt. is washed with distilled water.
• Then it is pulverized & sieved through 90# and stored
in dessicator over fused CaCl2.
• Eg. Ketoconazole
04/05/2012 145

Applications
• To increase aq. solubility
• To increase dissolution rate of drug
• To improve bioavailability of drug
• To increase chemical/physical stability
• To decrease drug irritation
04/05/2012 146

Crystallinity
• Crystal habit & internal structure of drug can affect
bulk & physicochemical property of molecule.
• Crystal habit is description of outer appearance of
crystal.
• Internal structure is molecular arrangement within the
solid.
04/05/2012 147

• Change with internal structure usually alters crystal
habit.
Eg. Conversion of sodium salt to its free acid form
produce both change in internal structure & crystal
habit.
04/05/2012 148
Crystallinity

Different shapes of crystals
• Cubic or isometric - not
always cube shaped. Also
find as octahedrons (eight
faces) and dodecahedrons
(10 faces).
• Tetragonal- similar to cubic
crystals, but longer along
one axis than the other,
forming double pyramids
and prisms.
• Orthorhombic - like
tetragonal crystals except
not square in cross section
(when viewing the crystal
on end), forming rhombic
prisms or dipyramids (two
pyramids stuck together).
• Hexagonal - six-sided
prisms. When you look at
the crystal on-end, the cross
section is a hexagon.
• Trigonal - possess a single
3-fold axis of rotation
instead of the 6-fold axis of
the hexagonal division.
• Triclinic - usually not
symmetrical from one side
to the other, which can lead
to some fairly strange
shapes.
• Monoclinic - like skewed
tetragonal crystals, often
forming prisms and double
pyramids.
04/05/2012 149

04/05/2012 150

• Depending on internal structure compounds is
classified as
1. Crystalline
2. Amorphous
• Crystalline compounds are characterized by
repetitious spacing of constituent atom or molecule in
three dimensional array.
• In amorphous form atom or molecule are randomly
placed.
04/05/2012 151

• Solubility & dissolution rate are greater for
amorphous form then crystalline, as amorphous form
has higher thermodynamic energy.
Eg. Amorphous form of Novobiocin is well absorbed
whereas crystalline form results in poor absorption.
04/05/2012 152

Polymorphism
• It is the ability of the compound to crystallize as more
than one distinct crystalline species with different
internal lattice.
• Different crystalline forms are called polymorphs.
• Polymorphs are of 2 types
1. Enatiotropic
2. Monotropic
04/05/2012 153

• The polymorph which can be changed from one form
into another by varying temp. or pressure is called as
Enantiotropic polymorph.
Eg. Sulfur.
• One polymorph which is unstable at all temp. &
pressure is called as Monotropic polymorph.
Eg. Glyceryl stearate.
04/05/2012 154
Polymorphism

• Polymorph differ from each other with respect to
their physical property such as
Solubility
Melting point
Density
Hardness
Compression characteristic
04/05/2012 155
Polymorphism

• During preformulation it is important to identify the
polymorph that is stable at room temp.
Eg. 1)Chloromphenicol exist in A,B & C forms,
of these B form is more stable & most
preferable.
2)Riboflavin has I,II & III forms, the III form
shows 20 times more water solubility than
form I.
04/05/2012 156
Polymorphism

Techniques for studies of
crystals
• Microscopy
• Hot stage microscopy
• Thermal analysis
• X-ray diffraction
04/05/2012 157

Microscopy
• Material with more than one refractive index are
anisotropic & appear bright with brilliant colors
against black polarized background.
• The color intensity depends upon crystal thickness.
• Isotropic material have single refractive index and
this substance do not transmit light with crossed
polarizing filter and appears black.
04/05/2012 158

Microscopy
• Advantage :
By this method, we can study crystal morphology &
difference between polymorphic form.
• Disadvantage :
This require a well trained optical crystallographer, as
there are many possible crystal habit & their
appearance at different orientation.
04/05/2012 159

Hot stage microscopy
• The polarizing microscope fitted with hot stage is
useful for investigating polymorphism, melting point
& transition temp.
• Disadvantage :
In this technique, the molecules can degrade during
the melting process.
04/05/2012 160

Hot stage microscopy
• Results of hot stage
microscopy
• Diagrammatic
representation
04/05/2012 161

Thermal analysis
• Differential scanning calorimetry (DSC) &
Differential thermal analysis are (DTA) are
particularly useful in the investigation of
polymorphism.
• It measures the heat loss or gain resulting from
physical or chemical changes within a sample as a
function of temp.
04/05/2012 162

Thermal analysis
• For characterizing crystal forms , the heat of fusion
can be obtained from the area under DSC- curve for
melting endotherms.
• Similarly, heat of transition from one polymorph to
another may be calculated.
• A sharp symmetric melting endotherm can indicate
relative purity of molecule.
04/05/2012 163

Thermal analysis
• A broad asymmetric curve indicates presence of
impurities.
• Disadvantage :
Degradation during thermal analysis may provide
misleading results.
04/05/2012 164

X-ray diffraction
• Working :
When beam of nonhomogenous X-ray is allow to
pass through the crystal, X-ray beam is diffracted & it
is recorded by means of photographic plate.
• Diffraction is due to crystal which acts as 3
dimensional diffraction grating toward X-ray.
04/05/2012 165

04/05/2012 166
X-ray diffraction

• Random orientation of crystal lattice in the powder
causes the X-ray to scatter in a reproducible pattern of
peak intensities.
• The diffraction pattern is characteristic of a specific
crystalline lattice for a given compound.
04/05/2012 167
X-ray diffraction

• An amorphous form does not produce a pattern
mixture of different crystalline forms.
• Single – Crystal x-ray provide the most complete
information about the solid state.
04/05/2012 168
X-ray diffraction

Stability testing….
04/05/2012 169

Why Stability?
• Provide a evidence on how the quality of a drug
substance or drug product varies with time under the
influence of a variety of environmental factors such
as….. temperature, Humidity and light.
• Establish a re-test period for the drug substance or a
shelf life for the drug product and recommended storage
conditions.
• Because physical, chemical or microbiological changes
might impact the efficiency and security of the final
product04/05/2012 170

Where and Why?
Stability Studies are preformed on ...
• Drug Substances (DS)  The unformulated drug
substance that may subsequently be formulated with
excipients to produce the dosage form.
• Drug Products (DP)  The dosage form in the final
immediate packaging intended for marketing…….
• controlled and documented determination of
acceptable changes of the drug substance or drug
product
04/05/2012 171

What are changes?
• Physical changes
• Appearance
• Melting point
• Clarity and color of solution
• moisture
• Crystal modification (Polymorphism)
• Particle size
• Chemical changes
• Increase in Degradation
• Decrease of Assay
• Microbial changes
04/05/2012 172

Forced degradation studies
• Acidic & Basic conditions.
• Dry heat exposure
• UV radiation exposure
• Influence of pH
• Influence of temperature
• Influence of ionic strength
04/05/2012 173

Arrhenius Equation
• K = Se-Ha /RT
where..k = specific rate of degradation.
R = gas constant ( 1.987 calories degree -1mole)
T = absolute temperature.
S = frequency factor.
Logarithmically ,
ln k = -Ha/ RT + ln S
converting to log 10
Log k = -ΔHa/2.303 R .1/T + log S
log k = specific rate of degradation
S = constant
04/05/2012 174

• Plot of log K v/s 1/T….yields a slope equal to -ΔHa/2.303 R …..
From which heat of activation (ΔHa) can be calculated.
• Log k2/k1 = ΔHa/2.303 R . ( T2 – T1 )/ T2.T1
Mean Kinetic Temperature
04/05/2012 175
Arrhenius Equation

ΔH/R
• Tk =
-ln ( e – DHRT1 + e -ΔH/R T2 +….+ e- ΔH/R Tn
n
Tk = Mean kinetic temp
H = Heat of activation (83.144 KJ/mole)
R = Universal gas constant (8.3144 . 10 1 – KJ/mole/degree )
T1 = average storage temp during first time period ( months)
T2 = average storage temp during second time period ( months)
Tn = average storage temp during nth time period ( months)
n = no of average temp recorded (min )
T = temp in o k ( degree kelvin )
Mean Kinetic Temperature
04/05/2012 176

Clasius – Clapeyron equation
• ln = P2 / P1 . ΔH V ( T2 – T1 ) / R ( T 2 _ T 1)
where…. P2 & P1 = vapour pressure at T1 & T 2
=molar ( latent ) heat of evaporation
Q =PD / PS . 100
RH is expressed in percentage ( %)
Q = Relative humidity
PD = partial pressure of unsaturated air
PS = saturation pressure
ΔH
Relative humidity
04/05/2012 177

Chemical degradation studies
• Hydrolysis
• Oxidation
• Reduction
• Decarboxylation
• Photolysis
04/05/2012 178

Stability studies at different
stages
• Stress- and accelerated Testing with drug substances
• Stability on pre-formulation batches
• Stress testing on scale-up Batches
• Accelerated and long term testing for registration
• On-going Stability testing
• Follow-up Stabilities
04/05/2012 179

Scope
• Solubility Profile
• Hygroscopicity
• Thermal stability
(Melting point,
Polymorphism)
• Chemical stability
􀂄 1 Batch
􀂄 Up to 3 month
Scope
• Determination of expire date
• Determination of preliminary
specifications
• Release of clinical batches
• Monitoring of samples during the clinical
phases
• Definition of storage conditions
• Definition of Tests for registration
stability
􀂄 Up to 36 month
􀂄 Selection of samples
• API, excipient, batches
􀂄 Scope
• Appearance
• Appropriate physical-chemical parameter
• Assay / Degradation products
􀂄 Up to 3 month
04/05/2012 180
Stability studies at different
stages

Testing scope for Solid dosage
• Physical-chemical properties
– Appearance
– Elasticity
– Mean mass
– Moisture
– Hardness
– Disintegration
– Dissolution
• Chemical properties
– Assay
– Degradation
• Microbial properties
• Container closure system properties
– Functionality tests (e.g. extraction from blister)
Tablet & Capsule
04/05/2012 181

Testing scope for Oral liquid
form
– pH
– Color & clarity of solution
– Viscosity
– Particle size distribution (for oral suspensions only)
– Assay
– Degradation products
– Degradation preservatives
– Content antioxidants
– Functionality tests
04/05/2012 182

Testing scope for
LIQUID FORMS for inj. and
PARENTRAL
– pH
– Loss on weight
– Color & clarity of solution
– Assay
– Degradation products
– Degradation preservatives
– Content antioxidants
04/05/2012 183

Testing scope for
SEMI LIQUID FORMS
– Appearance, odor, homogenesity, consistency
– Loss on weight, Viscosity
– Content uniformity (within the container)
– Assay
– Degradation products & preservatives
– Content preservatives
– Degradation– Content antioxidants
04/05/2012 184

Climatic Zones / Storage conditions
Climatic Zone
Countries
Calculated data
Temp. MKT humidity
°C °C % r.h.
Derived data
Temp humidity
°C % r.h.
Climatic Zone I
"Temperate"
Japan, United Kingdom,
Northern Europe,
Canada, Russia, United
States
20 20 42 21 45
Climatic Zone II
"Mediterranean,
Subtropical"
Japan, United States,
Southern Europe
26.4 22 52 25 60
04/05/2012 185

Climatic Zone
Countries
Calculated data
Temp. MKT humidity
°C °C % r.h.
Derived data
Temp humidity
°C % r.h.
Climatic Zone III
"Hot, dry"
Iran, Iraq, Sudan
26,4 27,9 35 30 35
Climatic Zone IV
"Hot, humid"
Brazil, Ghana, Indonesia,
Nicaragua,
Philippines
26,7 27,4 76
30 70
04/05/2012 186
Climatic Zones / Storage conditions

What or Who is ICH?
• ICH stands for International Conference on Harmonization of
Technical Requirements for Registration of Pharmaceuticals for
Human use
• Objectives of ICH
• Harmonization of registration applications within the three
regions of the EU, Japan and the United States.
• ICH is a joint initiative involving both regulators and industry
as equal partners in the scientific and technical discussions of
the testing procedures which are required to ensure and assess
the safety,quality and efficacy of medicines.
04/05/2012 187

What or Who is ICH?
There are Six Parties directly involved in the decision making
process
• EU: European Commission - European Union
• EFPIA: European Federation of Pharmaceutical Industries and
Associations
• MHLW: Ministry of Health, Labor and Welfare, Japan
• JPMA: Japan Pharmaceutical Manufacturers Association
• FDA: US Food and Drug Administration
• PhRMA: Pharmaceutical Research and Manufacturers of America
04/05/2012 188

• There are additionally observers installed to act as a
link with non-ICH countries and regions
• WHO
• The European Free Trade Area (EFTA),
represented by Swissmedic Switzerland
• Health Canada
٠Global guidelines
04/05/2012 189

ICH Guidelines
• Quality Guidelines “Q” (chemical and pharmaceutical QA)
– details see next slide
• Safety Guidelines “S” (in vitro and in vivo pre-clinical studies)
– covering Carcinogenicity Testing, Genotoxicity Testing,
Toxicokinetics and Pharmacokinetics ….. etc.
• Efficacy Guidelines “E” (clinical studies in human subject)
– Covering clinical safety, Dose Response Studies, Good
Clinical Practices, Clinical evaluation …. etc.
• Multidisciplinary Guidelines “M”
– Covering Medical Terminology, Electronic Standards for
Transmission of Regulatory Information …… etc.
– Important for Stability !
» Guideline M4: The Common Technical Document (CTD)
04/05/2012 190

ICH Q-Guidelines (Quality)
• Stability Testing in Climatic Zone I and II (Q1A)
• Photostability Testing (Q1B)
• Stability Testing for New Dosage Forms (Q1C)
• Bracketing and Matrixing Designs (Q1D)
• Evaluation of Stability Data (Q1E)
• Stability Testing in Climatic Zones III and IV
(Q1F)
• Validation of Analytical Procedures (Q2)
• Impurities (Q3)
• Biotechnological Products (Q5)
• Specifications (Q6)
04/05/2012 191

Q1A(R2) Stability testing of
New Drug Substances & Products
• Stability Testing in Climatic Zone I and II (Q1A)
• Photostability Testing (Q1B)
• Stability Testing for New Dosage Forms (Q1C)
• Bracketing and Matrixing Designs (Q1D)
• Evaluation of Stability Data (Q1E)
• Stability Testing in Climatic Zones III and IV
(Q1F)
• Validation of Analytical Procedures (Q2)
• Impurities (Q3)
• Biotechnological Products (Q5)
• Specifications (Q6)
04/05/2012 192

Study Storage condition
Minimum time period
covered by data at
submission
Long term 25°C ± 2°C / 60% ± 5% r.h or
30°C ± 2°C / 65% ± 5% r.h.
12 months
Intermediate 30°C ± 2°C / 65% ± 5% r.h. 6 months
Accelerated 40°C ± 2°C / 75% ± 5% r.h. 6 months
Drug substances - General case
Drug substances - intended for storage in a Refrigerator
Study Storage condition Minimum time period
covered by data at
submission
Long term 5°C ± 3°C 12 months
04/05/2012 193

Drug substances/Product- intended for storage in Freezer
covered by data at
submission
Long term -20°C ± 5°C 12 months
Drug products - General case
covered by data at
submission
Long term 25°C ± 2°C / 60% ± 5% r.h. or
30°C ± 2°C / 65% ± 5% r.h.
12 months
04/05/2012 194

Drug products - packaged in Semi-permeable containers
covered by data at
submission
Long term 25°C ± 2°C / 40% ± 5% r.h. or
30°C ± 2°C / 35% ± 5% r.h.
12 months
Drug products - intended for storage in a Refrigerator
covered by data at
submission
Long term 5°C ± 3°C 12 months
04/05/2012 195

. From the graph no : time period to have 90% potency for each temperature
namely 37°c, 45°c and 60°c were ascertained for Formulation F3 which are
depicted in the following table
Temperature under study Time required to have a 90%
potency (days) i.e.‘t’ 90%
37°C 262
45°C 192
60°C 95
CALCULATIONS FOR SHELF LIFE PREDICTION
‘t’ 90% values from the above table then convert into log ‘t’ 90% and their
coresponding temperature (t) into absolute temperature (‘T’). Then reciprocal of
absolute temperature 1/T was calculated at each temperature.
04/05/2012 196

AT 37°C
‘t’ 90% = 262
log ‘t’ 90% = 2.41
T = ‘t’+273
= 37+273
T =310 1/T=1/310=3.225*10-3
AT 45°C
‘t’ 90% = 192
log ‘t’ 90% = 2.28
T = ‘t’ +273
= 45+273
T =318 1/T=1/318=3.144*10-3
At 60°C
1/T=1/333=3.00*10-3
04/05/2012 197
CALCULATIONS FOR SHELF LIFE
PREDICTION

TABLE DEPICTING ‘t’ 90% ,1/T AND LOG ‘t’
90% VALUES FOR FORMULATION F3 AT
37°C, 45°C AND 60°C
Temperature
under study
‘t’ 90% (days) 1/T Log ‘t’ 90%
37°C 262 3.225*10-3 2.41
45°C 192 3.14*10-3 2.28
60°C 95 3.000*10-3 1.97
04/05/2012 198

• At 30°C(Room Temperature)
T = ‘t’ +273
= 30+273
T = 303 1/T=1/303=3.30*10-3
Depicts a plot between log t 90% and 1/T10-3 Formulation F3 at 37°C
, 45°C,60 °C. The straight line so obtained was extra plotted to 1/T
value at 30°C & the corresponding log ‘t’ at 30°C on y axis was
noted down. It was found to be 2.69.
Now log’ t’ 90% at 30°C = 2.69
‘t’ 90°C at 30°C = 490 days.
Therefore shelf life of formulation F3 in years = 490/365 = 1.342
years or = 1.3 years.
04/05/2012 199
TABLE DEPICTING ‘t’ 90% ,1/T AND LOG ‘t’
90% VALUES FOR FORMULATION F3 AT
37°C, 45°C AND 60°C

04/05/2012 204
Any Questions
on the
Recap units

REFERENCES
1. Ansel’s pharmaceutical Dosage forms & Drug delivery
systems, 8th edition by Loyd V. Allen, Nicholas G.popovich,
Howard C. Ansel, publised by B.I.Publication pvt. Ltd.,
page no:- 187-193,42 & 43,126-133.
2. Pharmaceutical preformulation by J.T.Cartensen published
by technomic publishing Co., page no:- 1-6, 211-212.
3. Textbook of physical pharmaceutics by C.V.S.
Subrahmanyam, published by Vallabh prakashan, page no:-
182-208, 222-226.
04/05/2012 206

4. The theory & practice of industrial pharmacy by
Leon Lachman, Herbert A. Lieberman, Joseph L.
kenig, 3rd edition, published by Varghese
Publishing house, page no:- 171-184.
5. Martin’s Physical pharmacy & Pharmaceutical
science, 5th edition by Patrick J. Sinco, Published by
Lippincott williams & wilkins, page no:- 547-550.
6. Pharmaceutical dosage forms : Tablet volume1,
edited by Herbert A. Lieberman & Leon Lachman,
published by Marcel dekker, page no:- 1-10.
04/05/2012 207
REFERENCES

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