Q3 c r5_ step4

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INTERNATIONAL CONFERENCE ON HARMONISATION OF TECHNICAL
REQUIREMENTS FOR REGISTRATION OF PHARMACEUTICALS FOR HUMAN USE

ICH HARMONISED TRIPARTITE GUIDELINE

IMPURITIES: GUIDELINE FOR RESIDUAL SOLVENTS
Q3C(R5)
Q3C(R5)

Current Step 4 version
dated 4 February 2011
Parent Guideline dated 17 July 1997
(Revised PDE for THF and NMP dated September 2002
and October 2002 incorporated in core Guideline in
November 2005 and revised PDE for Cumene incorporated
in core Guideline in February 2011)

This Guideline has been developed by the appropriate ICH Expert Working Group
and has been subject to consultation by the regulatory parties, in accordance with the
ICH Process. At Step 4 of the Process the final draft is recommended for adoption to
the regulatory bodies of the European Union, Japan and USA.


Q3C(R
Q3C(R5)
Document History
First
Codification

History

New
Codification
Nov. 2005
Nov.

Date

Parent Guideline: Impurities: Guideline for Residual Solvents
Q3C

Approval by the Steering Committee under Step 2 and release
for public consultation.

6
November
1996

Q3C

Q3C

Approval by the Steering Committee under Step 4 and
recommendation for adoption to the three ICH regulatory
bodies.

17 July
1997

Q3C

Revision of the PDE information for THF contained in the Parent Guideline
Q3C(M)
for THF

Permissible Daily Exposure (PDE) for Tetrahydrofuran (THF):
revision of PDE based on new toxicological data.

20 July
2000

in Q3C(R1)

12
September
2002

in Q3C(R1)

Approval by the Steering Committee of the new PDE for THF
under Step 2 and release for public consultation.
Q3C(M)
for THF

Approval by the Steering Committee under Step 4 and
bodies.

Revision of PDE information for NMP contained in the Parent Guideline
Q3C(M) for Permissible Daily Exposure (PDE) for N-Methylpyrrolidone
NMP
(NMP): revision of PDE based on new toxicological data.

20 July
2000

in Q3C(R2)

Q3C(M) for Approval by the Steering Committee under Step 4 and
NMP
bodies.

12
September
2002

in Q3C(R2)

Q3C(M) for Corrigendum to calculation formula approved by the Steering
NMP
Committee.

28 October
2002

in Q3C(R3)

Q3C, Q3C(M)
for THF and
Q3C(M) for
NMP

November
2005

Q3C(R3)

Approval by the Steering Committee of the Revision under Step
2 and release for public consultation.

The parent Guideline is now renamed Q3C(R3) as the two
updates (PDE for N-Methylpyrrolidone and PDE for
Tetrahydrofuran) and the corrigendum of the update for NMP
have been added to the parent Guideline.

Parent Guideline: Impurities: Guideline for Residual Solvents
Q3C(R4)

Update of Table 2, Table 3 and Appendix 1 to reflect the
revision of the PDEs for N-Methylpyrrolidone and
Tetrahydrofuran.

February
2009

Q3C(R4)

Cumene
Revision of PDE information for Cumene contained in the Parent Guideline
PDE for
Cumene

Permissible Daily Exposure (PDE) for Cumene: revision of
PDE based on new toxicological data.
Approval by the Steering Committee under Step 2 and release
for public consultation.

26 March
2010

in Q3C(R5)


Current Step 4 version
Q3C(R5)

Approval of the PDE for Cumene by the Steering Committee
under Step 4 and recommendation for adoption to the three
ICH regulatory bodies.
The PDE for Cumene document has been integrated as part IV
in the core Q3C(R4) Guideline which was then renamed
Q3C(R5).
The Table 2, Table 3 and Appendix 1 have been updated to
reflect the revision of the PDE for Cumene.

4 February
2011

Q3C(R5)


ICH Harmonised Tripartite Guideline

CONTENTS
TABLE OF CONTENTS

PART I:
1.

................................................................
...............................................................
INTRODUCTION ............................................................................................... 1

2.

................................................................
...........................................
SCOPE OF THE GUIDELINE ........................................................................... 1

3.

GENERAL PRINCIPLES....................................................................................
................................................................
GENERAL PRINCIPLES.................................................................................... 2

3.1

Classification of Residual Solvents by Risk Assessment ....................................... 2

3.2

Methods for Establishing Exposure Limits............................................................ 2

3.3

Options for Describing Limits of Class 2 Solvents................................................. 3

3.4

Analytical Procedures ............................................................................................. 4

3.5

Reporting levels of residual solvents ...................................................................... 4

4.

................................................................
...................................
LIMITS of RESIDUAL SOLVENTS ................................................................... 5

4.1

Solvents to Be Avoided............................................................................................ 5

4.2

Solvents to Be Limited ............................................................................................ 6

4.3

Solvents with Low Toxic Potential ......................................................................... 7

4.4

Solvents for which No Adequate Toxicological Data was Found........................... 8

.................................................................................................................
................................................................
GLOSSARY ................................................................................................................. 9
GUIDELINE
NE................
APPENDIX 1. LIST OF SOLVENTS INCLUDED IN THE GUIDELINE................ 10
ADDITIONAL
........................................................
APPENDIX 2. ADDITIONAL BACKGROUND ........................................................ 14
A2.1 Environmental Regulation of Organic Volatile Solvents ..................................... 14
A2.2 Residual Solvents in Pharmaceuticals ................................................................. 14
EXPOSURE LIMITS.................
APPENDIX 3. METHODS FOR ESTABLISHING EXPOSURE LIMITS................. 15
II:
PART II:
TETRAHYDROFURAN................................................................
RAN............................................................................
PDE FOR TETRAHYDROFURAN ............................................................................ 18
III:
PART III:
N(NMP)........................................................
MP)................................
PDE FOR N-METHYLPYRROLIDONE (NMP)........................................................ 20
IV:
PART IV:
.................................................................................................
................................................................
PDE FOR CUMENE ................................................................................................. 22

i


PART I:
Having reached Step 4 of the ICH Process at the ICH Steering Committee meeting on
17 July 1997, this Guideline is recommended for adoption
to the three regulatory parties to ICH

1.
INTRODUCTION
The objective of this guideline is to recommend acceptable amounts for residual
solvents in pharmaceuticals for the safety of the patient. The guideline recommends
use of less toxic solvents and describes levels considered to be toxicologically
acceptable for some residual solvents.
Residual solvents in pharmaceuticals are defined here as organic volatile chemicals
that are used or produced in the manufacture of drug substances or excipients, or in
the preparation of drug products. The solvents are not completely removed by
practical manufacturing techniques. Appropriate selection of the solvent for the
synthesis of drug substance may enhance the yield, or determine characteristics such
as crystal form, purity, and solubility. Therefore, the solvent may sometimes be a
critical parameter in the synthetic process. This guideline does not address solvents
deliberately used as excipients nor does it address solvates. However, the content of
solvents in such products should be evaluated and justified.
Since there is no therapeutic benefit from residual solvents, all residual solvents
should be removed to the extent possible to meet product specifications, good
manufacturing practices, or other quality-based requirements. Drug products should
contain no higher levels of residual solvents than can be supported by safety data.
Some solvents that are known to cause unacceptable toxicities (Class 1, Table 1)
should be avoided in the production of drug substances, excipients, or drug products
unless their use can be strongly justified in a risk-benefit assessment. Some solvents
associated with less severe toxicity (Class 2, Table 2) should be limited in order to
protect patients from potential adverse effects. Ideally, less toxic solvents (Class 3,
Table 3) should be used where practical. The complete list of solvents included in this
guideline is given in Appendix 1.
The lists are not exhaustive and other solvents can be used and later added to the
lists. Recommended limits of Class 1 and 2 solvents or classification of solvents may
change as new safety data becomes available. Supporting safety data in a marketing
application for a new drug product containing a new solvent may be based on
concepts in this guideline or the concept of qualification of impurities as expressed in
the guideline for drug substance (Q3A, Impurities in New Drug Substances) or drug
product (Q3B, Impurities in New Drug Products), or all three guidelines.
GUIDELINE
2.
SCOPE OF THE GUIDELINE
Residual solvents in drug substances, excipients, and in drug products are within the
scope of this guideline. Therefore, testing should be performed for residual solvents
when production or purification processes are known to result in the presence of such
solvents. It is only necessary to test for solvents that are used or produced in the
manufacture or purification of drug substances, excipients, or drug product. Although
manufacturers may choose to test the drug product, a cumulative method may be
used to calculate the residual solvent levels in the drug product from the levels in the

1


ingredients used to produce the drug product. If the calculation results in a level
equal to or below that recommended in this guideline, no testing of the drug product
for residual solvents need be considered. If, however, the calculated level is above the
recommended level, the drug product should be tested to ascertain whether the
formulation process has reduced the relevant solvent level to within the acceptable
amount. Drug product should also be tested if a solvent is used during its
manufacture.
This guideline does not apply to potential new drug substances, excipients, or drug
products used during the clinical research stages of development, nor does it apply to
existing marketed drug products.
The guideline applies to all dosage forms and routes of administration. Higher levels
of residual solvents may be acceptable in certain cases such as short term (30 days or
less) or topical application. Justification for these levels should be made on a case by
case basis.
See Appendix 2 for additional background information related to residual solvents.
3.

GENERAL PRINCIPLES

3.1 Classification of Residual Solvents by Risk Assessment
The term "tolerable daily intake" (TDI) is used by the International Program on
Chemical Safety (IPCS) to describe exposure limits of toxic chemicals and "acceptable
daily intake" (ADI) is used by the World Health Organization (WHO) and other
national and international health authorities and institutes. The new term
"permitted daily exposure" (PDE) is defined in the present guideline as a
pharmaceutically acceptable intake of residual solvents to avoid confusion of differing
values for ADI's of the same substance.
Residual solvents assessed in this guideline are listed in Appendix 1 by common names
and structures. They were evaluated for their possible risk to human health and placed
into one of three classes as follows:

Class 1 solvents: Solvents to be avoided
Known human carcinogens, strongly suspected human carcinogens, and
environmental hazards.

Class 2 solvents: Solvents to be limited
Non-genotoxic animal carcinogens or possible causative agents of other
irreversible toxicity such as neurotoxicity or teratogenicity.
Solvents suspected of other significant but reversible toxicities.

Class 3 solvents: Solvents with low toxic potential
Solvents with low toxic potential to man; no health-based exposure limit is
needed. Class 3 solvents have PDEs of 50 mg or more per day.
3.2 Methods for Establishing Exposure Limits
The method used to establish permitted daily exposures for residual solvents is
presented in Appendix 3. Summaries of the toxicity data that were used to establish
limits are published in Pharmeuropa, Vol. 9, No. 1, Supplement, April 1997.

2


Solvents
3.3 Options for Describing Limits of Class 2 Solvents
Two options are available when setting limits for Class 2 solvents.

Option 1: The concentration limits in ppm stated in Table 2 can be used. They were
calculated using equation (1) below by assuming a product mass of 10 g administered
daily.

Concentration (ppm) =

1000 x PDE
dose

(1)

Here, PDE is given in terms of mg/day and dose is given in g/day.
These limits are considered acceptable for all substances, excipients, or products.
Therefore this option may be applied if the daily dose is not known or fixed. If all
excipients and drug substances in a formulation meet the limits given in Option 1,
then these components may be used in any proportion. No further calculation is
necessary provided the daily dose does not exceed 10 g. Products that are
administered in doses greater than 10 g per day should be considered under Option 2.

Option 2: It is not considered necessary for each component of the drug product to
comply with the limits given in Option 1. The PDE in terms of mg/day as stated in
Table 2 can be used with the known maximum daily dose and equation (1) above to
determine the concentration of residual solvent allowed in drug product. Such limits
are considered acceptable provided that it has been demonstrated that the residual
solvent has been reduced to the practical minimum. The limits should be realistic in
relation to analytical precision, manufacturing capability, reasonable variation in the
manufacturing process, and the limits should reflect contemporary manufacturing
standards.
Option 2 may be applied by adding the amounts of a residual solvent present in each
of the components of the drug product. The sum of the amounts of solvent per day
should be less than that given by the PDE.
Consider an example of the use of Option 1 and Option 2 applied to acetonitrile in a
drug product. The permitted daily exposure to acetonitrile is 4.1 mg per day; thus,
the Option 1 limit is 410 ppm. The maximum administered daily mass of a drug
product is 5.0 g, and the drug product contains two excipients. The composition of the
drug product and the calculated maximum content of residual acetonitrile are given
in the following table.

Component

Amount in
formulation

Acetonitrile content Daily exposure

Drug substance

0.3 g

800 ppm

0.24 mg

Excipient 1

0.9 g

400 ppm

0.36 mg

Excipient 2

3.8 g

800 ppm

3.04 mg

Drug Product

5.0 g

728 ppm

3.64 mg

Excipient 1 meets the Option 1 limit, but the drug substance, excipient 2, and drug
product do not meet the Option 1 limit. Nevertheless, the product meets the Option 2
limit of 4.1 mg per day and thus conforms to the recommendations in this guideline.

3


Consider another example using acetonitrile as residual solvent. The maximum
administered daily mass of a drug product is 5.0 g, and the drug product contains two
excipients. The composition of the drug product and the calculated maximum content
of residual acetonitrile are given in the following table.

Component

Amount in
formulation

Acetonitrile content Daily exposure

Drug substance

0.3 g

800 ppm

0.24 mg

Excipient 1

0.9 g

2000 ppm

1.80 mg

Excipient 2

3.8 g

800 ppm

3.04 mg

Drug Product

5.0 g

1016 ppm

5.08 mg

In this example, the product meets neither the Option 1 nor the Option 2 limit
according to this summation. The manufacturer could test the drug product to
determine if the formulation process reduced the level of acetonitrile. If the level of
acetonitrile was not reduced during formulation to the allowed limit, then the
manufacturer of the drug product should take other steps to reduce the amount of
acetonitrile in the drug product. If all of these steps fail to reduce the level of residual
solvent, in exceptional cases the manufacturer could provide a summary of efforts
made to reduce the solvent level to meet the guideline value, and provide a riskbenefit analysis to support allowing the product to be utilised with residual solvent at
a higher level.
3.4 Analytical Procedures
Residual solvents are typically determined using chromatographic techniques such as
gas chromatography. Any harmonised procedures for determining levels of residual
solvents as described in the pharmacopoeias should be used, if feasible. Otherwise,
manufacturers would be free to select the most appropriate validated analytical
procedure for a particular application. If only Class 3 solvents are present, a nonspecific method such as loss on drying may be used.
Validation of methods for residual solvents should conform to ICH guidelines Text on
Validation of Analytical Procedures and Extension of the ICH Text on Validation of
Analytical Procedures.
Reporting
3.5 Reporting levels of residual solvents
Manufacturers of pharmaceutical products need certain information about the
content of residual solvents in excipients or drug substances in order to meet the
criteria of this guideline. The following statements are given as acceptable examples
of the information that could be provided from a supplier of excipients or drug
substances to a pharmaceutical manufacturer. The supplier might choose one of the
following as appropriate:
•

Only Class 3 solvents are likely to be present. Loss on drying is less than 0.5%.

•

Only Class 2 solvents X, Y, ... are likely to be present. All are below the Option 1
limit. (Here the supplier would name the Class 2 solvents represented by X, Y, ...)

•

Only Class 2 solvents X, Y, ... and Class 3 solvents are likely to be present.
Residual Class 2 solvents are below the Option 1 limit and residual Class 3
solvents are below 0.5%.

4


If Class 1 solvents are likely to be present, they should be identified and quantified.
"Likely to be present" refers to the solvent used in the final manufacturing step and
to solvents that are used in earlier manufacturing steps and not removed consistently
by a validated process.
If solvents of Class 2 or Class 3 are present at greater than their Option 1 limits or
0.5%, respectively, they should be identified and quantified.
4.

SOLVENTS
LIMITS OF RESIDUAL SOLVENTS

4.1 Solvents to Be Avoided
Solvents in Class 1 should not be employed in the manufacture of drug substances,
excipients, and drug products because of their unacceptable toxicity or their
deleterious environmental effect. However, if their use is unavoidable in order to
produce a drug product with a significant therapeutic advance, then their levels
should be restricted as shown in Table 1, unless otherwise justified. 1,1,1Trichloroethane is included in Table 1 because it is an environmental hazard. The
stated limit of 1500 ppm is based on a review of the safety data.
TABLE 1. Class 1 solvents in pharmaceutical products (solvents that should be
avoided).

Solvent

Concentration limit
(ppm)

Concern

Benzene

2

Carcinogen

Carbon tetrachloride

4

Toxic and environmental
hazard

1,2-Dichloroethane

5

Toxic

1,1-Dichloroethene

8

Toxic

1500

Environmental hazard

1,1,1-Trichloroethane

5


4.2 Solvents to Be Limited
Solvents in Table 2 should be limited in pharmaceutical products because of
their inherent toxicity. PDEs are given to the nearest 0.1 mg/day, and
concentrations are given to the nearest 10 ppm. The stated values do not
reflect the necessary analytical precision of determination. Precision should be
determined as part of the validation of the method.
TABLE 2. Class 2 solvents in pharmaceutical products.

Solvent

PDE (mg/day)

Concentration limit
(ppm)

Acetonitrile
Chlorobenzene

4.1
3.6

410
360

Chloroform

0.6

60

Cumene1

0.7

70

Cyclohexane

38.8

3880

1,2-Dichloroethene

18.7

1870

Dichloromethane

6.0

600

1,2-Dimethoxyethane

1.0

100

N,N-Dimethylacetamide

10.9

1090

N,N-Dimethylformamide

8.8

880

1,4-Dioxane

3.8

380

2-Ethoxyethanol

1.6

160

Ethyleneglycol

6.2

620

Formamide

2.2

220

Hexane

2.9

290

Methanol

30.0

3000

2-Methoxyethanol

0.5

50

Methylbutyl ketone

0.5

50

Methylcyclohexane

11.8

1180

N-Methylpyrrolidone2

5.3

530

Nitromethane

0.5

50

Pyridine

2.0

200

Sulfolane

1.6

160

The information included for Cumene reflects that included in the Revision of PDE
Information for Cumene which reached Step 4 in February 2011 and was subsequently

1

incorporated into the core Guideline. See Part IV (pages 22-25).
The information included for N-Methylpyrrolidone reflects that included in the Revision of
PDE Information for NMP which reached Step 4 in September 2002 (two mistyping corrections

2

made in October 2002), and was incorporated into the core guideline in November 2005. See
Part III (pages 20-21).

6


Tetrahydrofuran3

7.2

720

Tetralin

1.0

100

Toluene

8.9

890

1,1,2-Trichloroethene

0.8

80

Xylene*

21.7

2170

*usually

60% m-xylene, 14% p-xylene, 9% o-xylene with 17% ethyl benzene

4.3 Solvents with Low Toxic Potential
Solvents in Class 3 (shown in Table 3) may be regarded as less toxic and of lower risk
to human health. Class 3 includes no solvent known as a human health hazard at
levels normally accepted in pharmaceuticals. However, there are no long-term
toxicity or carcinogenicity studies for many of the solvents in Class 3. Available data
indicate that they are less toxic in acute or short-term studies and negative in
genotoxicity studies. It is considered that amounts of these residual solvents of 50 mg
per day or less (corresponding to 5000 ppm or 0.5% under Option 1) would be
acceptable without justification. Higher amounts may also be acceptable provided
they are realistic in relation to manufacturing capability and good manufacturing
practice.
qualityTABLE 3. Class 3 solvents which should be limited by GMP or other quality-based
requirements.
requirements.
Acetic acid

Heptane

Acetone

Isobutyl acetate

Anisole

Isopropyl acetate

1-Butanol

Methyl acetate

2-Butanol

3-Methyl-1-butanol

Butyl acetate

Methylethyl ketone

tert-Butylmethyl ether

Methylisobutyl ketone

Dimethyl sulfoxide

2-Methyl-1-propanol

Ethanol

Pentane

Ethyl acetate

1-Pentanol

Ethyl ether

1-Propanol

Ethyl formate

2-Propanol

Formic acid

Propyl acetate

3 The information included for Tetrahydrofuran reflects that included in the Revision of PDE
Information for THF which reached Step 4 in September 2002, and was incorporated into the

core guideline in November 2005. See Part II (pages 18-19).

7


4.4 Solvents for which No Adequate Toxicological Data was Found
The following solvents (Table 4) may also be of interest to manufacturers of
excipients, drug substances, or drug products. However, no adequate toxicological
data on which to base a PDE was found. Manufacturers should supply justification
for residual levels of these solvents in pharmaceutical products.
which
TABLE 4. Solvents for which no adequate toxicological data was found.
1,1-Diethoxypropane

Methylisopropyl ketone

1,1-Dimethoxymethane

Methyltetrahydrofuran

2,2-Dimethoxypropane

Petroleum ether

Isooctane

Trichloroacetic acid

Isopropyl ether

Trifluoroacetic acid

8


GLOSSARY
Genotoxic Carcinogens:
Genotoxic Carcinogens:
Carcinogens which produce cancer by affecting genes or chromosomes.
LOEL:
Abbreviation for lowest-observed effect level.
LowestLevel:
Lowest-Observed Effect Level:
The lowest dose of substance in a study or group of studies that produces biologically
significant increases in frequency or severity of any effects in the exposed humans or
animals.
Factor:
Modifying Factor:
A factor determined by professional judgment of a toxicologist and applied to bioassay
data to relate that data safely to humans.
Neurotoxicity:
eurotoxicity:
The ability of a substance to cause adverse effects on the nervous system.
NOEL:
Abbreviation for no-observed-effect level.
No-ObservedLevel:
No-Observed-Effect Level:
The highest dose of substance at which there are no biologically significant increases
in frequency or severity of any effects in the exposed humans or animals.
PDE:
Abbreviation for permitted daily exposure.
Exposure:
Permitted Daily Exposure:
The maximum acceptable intake per day of residual solvent in pharmaceutical
products.
Toxicity
Reversible Toxicity:
The occurrence of harmful effects that are caused by a substance and which
disappear after exposure to the substance ends.
Carcinogen:
Strongly Suspected Human Carcinogen:
A substance for which there is no epidemiological evidence of carcinogenesis but there
are positive genotoxicity data and clear evidence of carcinogenesis in rodents.
Teratogenicity:
Teratogenicity:
The occurrence of structural malformations in a developing fetus when a substance is
administered during pregnancy.

9


APPENDIX 1. LIST OF SOLVENTS INCLUDED IN THE GUIDELINE

Solvent

Other Names

Structure

Class

Acetic acid

Ethanoic acid

CH3COOH

Class 3

Acetone

2-Propanone

CH3COCH3

Class 3

CH3CN

Class 2

Propan-2-one
Acetonitrile
Anisole

Methoxybenzene

Benzene

Benzol

1-Butanol

n-Butyl alcohol

OCH3

Class 3
Class 1

CH3(CH2)3OH

Class 3

CH3CH2CH(OH)CH3

Class 3

Butan-1-ol
2-Butanol

sec-Butyl alcohol
Butan-2-ol

Butyl acetate

Acetic acid butyl ester

CH3COO(CH2)3CH3

Class 3

tert-Butylmethyl

2-Methoxy-2-methylpropane

(CH3)3COCH3

Class 3

ether
Carbon tetrachloride

Tetrachloromethane

CCl4

Class 1

Cl

Chlorobenzene
Chloroform

Trichloromethane

Cumene1

Isopropylbenzene

Class 2

CHCl3

Class 2

CH(CH3)2

Class 2

(1-Methyl)ethylbenzene
Cyclohexane

Hexamethylene

Class 2

1,2-Dichloroethane

sym-Dichloroethane

CH2ClCH2Cl

Class 1

Ethylene dichloride
Ethylene chloride

The information included for Cumene reflects that included in the Revision of PDE
Information for Cumene which reached Step 4 in February 2011 and was subsequently

1

incorporated into the core Guideline. See Part IV (pages 22-25).

10


Solvent

Other Names

Structure

Class

1,1-Dichloroethene

1,1-Dichloroethylene

H2C=CCl2

Class 1

ClHC=CHCl

Class 2

Vinylidene chloride
1,2-Dichloroethene

1,2-Dichloroethylene
Acetylene dichloride

Dichloromethane

Methylene chloride

CH2Cl2

Class 2

1,2-Dimethoxyethane

Ethyleneglycol dimethyl
ether

H3COCH2CH2OCH3

Class 2

Monoglyme
Dimethyl Cellosolve
N,NDimethylacetamide

DMA

CH3CON(CH3)2

Class 2

N,NDimethylformamide

DMF

HCON(CH3)2

Class 2

Dimethyl sulfoxide

Methylsulfinylmethane

(CH3)2SO

Class 3

Methyl sulfoxide
DMSO
1,4-Dioxane

p-Dioxane

O

O

Class 2

[1,4]Dioxane
Ethanol

Ethyl alcohol

CH3CH2OH

Class 3

2-Ethoxyethanol

Cellosolve

CH3CH2OCH2CH2OH

Class 2

Ethyl acetate

Acetic acid ethyl ester

CH3COOCH2CH3

Class 3

Ethyleneglycol

1,2-Dihydroxyethane

HOCH2CH2OH

Class 2

CH3CH2OCH2CH3

Class 3

1,2-Ethanediol
Ethyl ether

Diethyl ether
Ethoxyethane
1,1’-Oxybisethane

Ethyl formate

Formic acid ethyl ester

HCOOCH2CH3

Class 3

Formamide

Methanamide

HCONH2

Class 2

HCOOH

Class 3

CH3(CH2)5CH3

Class 3

Formic acid
Heptane

n-Heptane

11


Solvent

Other Names

Structure

Class

Hexane

n-Hexane

CH3(CH2)4CH3

Class 2

Isobutyl acetate

Acetic acid isobutyl ester

CH3COOCH2CH(CH3)2

Class 3

Isopropyl acetate

Acetic
ester

Methanol

acid

isopropyl CH3COOCH(CH3)2

Class 3

Methyl alcohol

CH3OH

Class 2

2-Methoxyethanol

Methyl Cellosolve

CH3OCH2CH2OH

Class 2

Methyl acetate

Acetic acid methyl ester

CH3COOCH3

Class 3

3-Methyl-1-butanol

Isoamyl alcohol

(CH3)2CHCH2CH2OH

Class 3

CH3(CH2)3COCH3

Class 2

Isopentyl alcohol
3-Methylbutan-1-ol
Methylbutyl ketone

2-Hexanone
Hexan-2-one

Methylcyclohexane

Cyclohexylmethane

Methylethyl ketone

2-Butanone

CH3

Class 2

CH3CH2COCH3

Class 3

CH3COCH2CH(CH3)2

Class 3

(CH3)2CHCH2OH

Class 3

MEK
Butan-2-one
Methylisobutyl
ketone

4-Methylpentan-2-one
4-Methyl-2-pentanone
MIBK

2-Methyl-1-propanol

Isobutyl alcohol
2-Methylpropan-1-ol

N-Methylpyrrolidone

1-Methylpyrrolidin-2-one
1-Methyl-2-pyrrolidinone

Nitromethane

Class 2
N

O

CH3

CH3NO2

Class 2

Pentane

n-Pentane

CH3(CH2)3CH3

Class 3

1-Pentanol

Amyl alcohol

CH3(CH2)3CH2OH

Class 3

Pentan-1-ol
Pentyl alcohol

12


Solvent

Other Names

Structure

Class

1-Propanol

Propan-1-ol

CH3CH2CH2OH

Class 3

(CH3)2CHOH

Class 3

CH3COOCH2CH2CH3

Class 3

Propyl alcohol
2-Propanol

Propan-2-ol
Isopropyl alcohol

Propyl acetate

Acetic acid propyl ester

Pyridine

Class 2

N

Sulfolane

Tetrahydrothiophene 1,1dioxide

Class 2
O

Tetrahydrofuran2

S

O

Tetramethylene oxide

Class 2
O

Oxacyclopentane
Tetralin

1,2,3,4-Tetrahydronaphthalene

Class 2

Toluene

Methylbenzene

1,1,1-Trichloroethane

Methylchloroform

CH3CCl3

Class 1

1,1,2-Trichloroethene

Trichloroethene

HClC=CCl2

Class 2

Xylene*

Dimethybenzene

CH3

Class 2

Class 2

CH3

CH3

Xylol
*usually

60% m-xylene, 14% p-xylene, 9% o-xylene with 17% ethyl benzene

2 The information included for Tetrahydrofuran reflects that included in the Revision of PDE
Information for THF which reached Step 4 in September 2002, and was incorporated into the

core guideline in November 2005. See Part II (pages 18-19).

13


ADDITIONAL
APPENDIX 2. ADDITIONAL BACKGROUND
A2.1 Environmental Regulation of Organic Volatile Solvents
Several of the residual solvents frequently used in the production of pharmaceuticals
are listed as toxic chemicals in Environmental Health Criteria (EHC) monographs and
the Integrated Risk Information System (IRIS). The objectives of such groups as the
International Programme on Chemical Safety (IPCS), the United States Environmental
Protection Agency (USEPA), and the United States Food and Drug Administration
(USFDA) include the determination of acceptable exposure levels. The goal is
protection of human health and maintenance of environmental integrity against the
possible deleterious effects of chemicals resulting from long-term environmental
exposure. The methods involved in the estimation of maximum safe exposure limits are
usually based on long-term studies. When long-term study data are unavailable,
shorter term study data can be used with modification of the approach such as use of
larger safety factors. The approach described therein relates primarily to long-term or
life-time exposure of the general population in the ambient environment, i.e., ambient
air, food, drinking water and other media.
A2.2 Residual Solvents in Pharmaceuticals
Exposure limits in this guideline are established by referring to methodologies and
toxicity data described in EHC and IRIS monographs. However, some specific
assumptions about residual solvents to be used in the synthesis and formulation of
pharmaceutical products should be taken into account in establishing exposure
limits. They are:
1)

Patients (not the general population) use pharmaceuticals to treat their diseases
or for prophylaxis to prevent infection or disease.

2)

The assumption of life-time patient exposure is not necessary for most
pharmaceutical products but may be appropriate as a working hypothesis to
reduce risk to human health.

3)

Residual solvents are unavoidable components in pharmaceutical production and
will often be a part of drug products.

4)

Residual solvents should not exceed recommended levels except in exceptional
circumstances.

5)

Data from toxicological studies that are used to determine acceptable levels for
residual solvents should have been generated using appropriate protocols such as
those described for example by OECD, EPA, and the FDA Red Book.

14


ESTABLISHING
APPENDIX 3. METHODS FOR ESTABLISHING EXPOSURE LIMITS
The Gaylor-Kodell method of risk assessment (Gaylor, D. W. and Kodell, R. L.: Linear
Interpolation algorithm for low dose assessment of toxic substance. J Environ.
Pathology, 4, 305, 1980) is appropriate for Class 1 carcinogenic solvents. Only in
cases where reliable carcinogenicity data are available should extrapolation by the
use of mathematical models be applied to setting exposure limits. Exposure limits for
Class 1 solvents could be determined with the use of a large safety factor (i.e., 10,000
to 100,000) with respect to the no-observed-effect level (NOEL). Detection and
quantitation of these solvents should be by state-of-the-art analytical techniques.
Acceptable exposure levels in this guideline for Class 2 solvents were established by
calculation of PDE values according to the procedures for setting exposure limits in
pharmaceuticals (Pharmacopeial Forum, Nov-Dec 1989), and the method adopted by
IPCS for Assessing Human Health Risk of Chemicals (Environmental Health Criteria
170, WHO, 1994). These methods are similar to those used by the USEPA (IRIS) and
the USFDA (Red Book) and others. The method is outlined here to give a better
understanding of the origin of the PDE values. It is not necessary to perform these
calculations in order to use the PDE values tabulated in Section 4 of this document.
PDE is derived from the no-observed-effect level (NOEL), or the lowest-observed
effect level (LOEL) in the most relevant animal study as follows:

PDE =

NOEL x Weight Adjustment
F1 x F2 x F3 x F4 x F5

(1)

The PDE is derived preferably from a NOEL. If no NOEL is obtained, the LOEL may
be used. Modifying factors proposed here, for relating the data to humans, are the
same kind of "uncertainty factors" used in Environmental Health Criteria
(Environmental Health Criteria 170, World Health Organization, Geneva, 1994), and
"modifying factors" or "safety factors" in Pharmacopeial Forum. The assumption of
100% systemic exposure is used in all calculations regardless of route of
administration.
The modifying factors are as follows:
F1 = A factor to account for extrapolation between species
F1 = 5 for extrapolation from rats to humans
F1 = 12 for extrapolation from mice to humans
F1 = 2 for extrapolation from dogs to humans
F1 = 2.5 for extrapolation from rabbits to humans
F1 = 3 for extrapolation from monkeys to humans
F1 = 10 for extrapolation from other animals to humans
F1 takes into account the comparative surface area:body weight ratios for the species
concerned and for man. Surface area (S) is calculated as:
(2)
S = kM0.67
in which M = body mass, and the constant k has been taken to be 10. The body
weights used in the equation are those shown below in Table A3.1.

15


F2 = A factor of 10 to account for variability between individuals
A factor of 10 is generally given for all organic solvents, and 10 is used consistently in
this guideline.
F3 = A variable factor to account for toxicity studies of short-term exposure
F3 = 1 for studies that last at least one half lifetime (1 year for rodents or rabbits;
7 years for cats, dogs and monkeys).
F3 = 1 for reproductive studies in which the whole period of organogenesis is
covered.
F3 = 2 for a 6-month study in rodents, or a 3.5-year study in non-rodents.
F3 = 5 for a 3-month study in rodents, or a 2-year study in non-rodents.
F3 = 10 for studies of a shorter duration.
In all cases, the higher factor has been used for study durations between the time
points, e.g., a factor of 2 for a 9-month rodent study.
F4 = A factor that may be applied in cases of severe toxicity, e.g., non-genotoxic
carcinogenicity, neurotoxicity or teratogenicity. In studies of reproductive toxicity, the
following factors are used:
F4 = 1 for fetal toxicity associated with maternal toxicity
F4 = 5 for fetal toxicity without maternal toxicity
F4 = 5 for a teratogenic effect with maternal toxicity
F4 = 10 for a teratogenic effect without maternal toxicity
F5 = A variable factor that may be applied if the no-effect level was not established
When only an LOEL is available, a factor of up to 10 could be used depending on the
severity of the toxicity.
The weight adjustment assumes an arbitrary adult human body weight for either sex
of 50 kg. This relatively low weight provides an additional safety factor against the
standard weights of 60 kg or 70 kg that are often used in this type of calculation. It is
recognized that some adult patients weigh less than 50 kg; these patients are
considered to be accommodated by the built-in safety factors used to determine a
PDE. If the solvent was present in a formulation specifically intended for pediatric
use, an adjustment for a lower body weight would be appropriate.
As an example of the application of this equation, consider a toxicity study of
acetonitrile in mice that is summarized in Pharmeuropa, Vol. 9, No. 1, Supplement,
April 1997, page S24. The NOEL is calculated to be 50.7 mg kg-1 day-1. The PDE for
acetonitrile in this study is calculated as follows:

50.7 mg kg -1 day -1 x 50 kg
PDE =
= 4.22 mg day -1
12 x 10 x 5 x 1 x 1
In this example,
F1 = 12 to account for the extrapolation from mice to humans
F2 = 10 to account for differences between individual humans
F3 = 5 because the duration of the study was only 13 weeks
F4 = 1 because no severe toxicity was encountered
F5 = 1 because the no effect level was determined

16


A3.1.
Table A3.1. Values used in the calculations in this document.
rat body weight

425 g

mouse respiratory volume

43 L/day

pregnant rat body weight

330 g

rabbit respiratory volume

1440 L/day

mouse body weight

28 g

guinea
volume

pregnant
weight

mouse

body 30 g

pig

respiratory 430 L/day

human respiratory volume

28,800
L/day

dog respiratory volume

9,000 L/day

monkey respiratory volume

1,150 L/day

4 kg

mouse water consumption

5 mL/day

beagle dog body weight

11.5 kg

rat water consumption

30 mL/day

rat respiratory volume

290 L/day

rat food consumption

30 g/day

guinea pig body weight
Rhesus
monkey
weight
rabbit body weight
(pregnant or not)

500 g

body 2.5 kg

The equation for an ideal gas, PV = nRT, is used to convert concentrations of gases
used in inhalation studies from units of ppm to units of mg/L or mg/m3. Consider as
an example the rat reproductive toxicity study by inhalation of carbon tetrachloride
(molecular weight 153.84) is summarized in Pharmeuropa, Vol. 9, No. 1, Supplement,
April 1997, page S9.

n
P
300 x 10 -6 atm x 153840 mg mol -1
46.15 mg
=
=
=
= 1.89 mg / L
-1
-1
V
RT
0.082 L atm K mol x 298 K
24.45 L
The relationship 1000 L = 1 m3 is used to convert to mg/ m3.

17


PART II:
IMPURITIES: RESIDUAL SOLVENTS (MAINTENANCE)
PDE FOR TETRAHYDROFURAN
Having reached Step 4 of the ICH Process at the ICH Steering Committee meeting
on 12 September, 2002 and incorporated into the core Guideline in November 2005,
this Guideline is recommended for
adoption to the three regulatory parties to ICH

The ICH Q3C guidance reached Step 5 in December of 1997. It had been agreed
by the members of the Expert Working Group (EWG) that the permissible daily
exposure (PDE) could be modified if reliable and more relevant toxicity data was
brought to the attention of the group. In 1999, a maintenance agreement was
instituted and a Maintenance EWG was formed. The agreement provided for the
re-visitation of solvent PDEs and allowed for minor changes to the guidance that
included the existing PDEs. It was also agreed that new solvents and PDEs could
be added based upon adequate toxicity data.
The EWG visited new toxicity data for the solvent tetrahydrofuran (THF) late last
year and earlier this year. The data in review was the information published by
the U. S. National Toxicology Program (NTP) that consisted of data from several
mutagenicity studies and two carcinogenicity studies in rodents via the
inhalational route of administration. Information was sent to the members of the
EWG for their analysis.
Animal Toxicity
Genetic toxicology studies were conducted in Salmonella typhimurium, Chinese
hamster ovary cells, Drosophila melanogaster, mouse bone marrow cells and
mouse peripheral blood cells. The in vitro studies were conducted with and
without exogenous metabolic activation from induced S9 liver enzymes. With the
exception of an equivocal small increase above baseline in male mouse
erythrocytes, no positive findings were found in any of the genetic toxicology
studies.
Groups of 50 male and 50 female rats were exposed to 0, 200, 600, or 1,800 ppm
tetrahydrofuran by inhalation, 6 hours per day, 5 days per week, for 105 weeks.
Identical exposures were given to groups of 50 male and 50 female mice. Under
the conditions of the studies, there was some evidence of carcinogenic activity of
THF in male rats due to increased incidences of adenoma or carcinoma (combined)
of the kidney. There was clear evidence of carcinogenic activity of THF in female
mice due to increased incidences of hepatocellular adenomas and carcinomas. No
evidence for carcinogenicity was found in female rats and male mice.

18


Using the lowest THF exposure in the most sensitive specie, the male rat at 200
ppm was used for the PDE calculation.

200 ppm =

200 x 72.10
= 589.8 mg/m 3 = 0.59 mg/L
24.45

For continuous dosing =

Daily dose =

PDE =

0.59 x 6 x 5
= 0.105 mg/L
24 x 7

0.105 x 290
= 71.65 mg/kg
0.425

71.65 x 50
= 7.165 mg/day = 7.2 mg/day
5 x 10 x 1 x 10 x 1
Limit =

7.2 x 1000
= 720 ppm
10

Conclusion:
The former PDE for this solvent was greater than 50 mg/day (121 mg/day) and
THF was placed in Class 3. The newly calculated PDE for tetrahydrofuran based
upon chronic toxicity/carcinogenicity data is 7.2 mg/day, therefore, it is
recommended that Tetrahydrofuran be placed into Class 2 in Table 2 in the ICH
Impurities: Residual Solvents Guideline. This is also the appropriate Class for
THF because this Class contains those solvents that are non-genotoxic
carcinogens and THF has been demonstrated to be a non-genotoxic carcinogen in
rodents.

19

PART III:
IMPURITIES : RESIDUAL SOLVENTS (MAINTENANCE)
PDE FOR N-METHYLPYRROLIDONE (NMP)
Having reached Step 4 of the ICH Process at the ICH Steering Committee meeting
on 12 September 2002 and incorporated into the core Guideline in November 2005,
this Guideline is recommended for

(Two mistyping corrections in the first calculation formula have been given
on October 28, 2002 – this version is corrected)
The ICH Q3C guidance reached Step 5 in December of 1997. It had been agreed
by the members of the Expert Working Group (EWG) that the permissible daily
exposure (PDE) could be modified if reliable and more relevant toxicity data was
brought to the attention of the group. In 1999, a maintenance agreement was
instituted and a Maintenance EWG was formed. The agreement provided for the
re-visitation of solvent PDEs and allowed for minor changes to the guidance that
included the existing PDEs. It was also agreed that new solvents and PDEs could
be added based upon adequate toxicity data.
The EWG received new toxicity data for the solvent N-methylpyrrolidone late last
year. It had been provided to the FDA by the NMP Producers Group. It was a 2year chronic feeding study in rats performed by E.I. Dupont de Nemours & Co
(unpublished data). The data was sent to the members of the EWG for their
analysis. At the time, that data appeared to be the best available upon which to
make a recommendation to the Steering Committee regarding a change in the
status of NMP. At the last ICH meeting, February 28 to March 2, 2000, I briefed
the Steering Committee on the results of the EWG’s analysis and its consensus
decision. The consensus was to remove NMP from Class 2 (PDE of 48.4 mg/day)
and place it into Class 3 with a new PDE of 207 mg/day. Shortly thereafter,
members of the EWG provided additional comment and data from which lower
PDEs could be determined. The following paragraphs contain an analysis of an
appropriate and more sensitive study from which to calculate a new PDE.
Animal Toxicity
The following paper was used for the calculation of the PDE for NMP:
“Effects Of Prenatal Exposure To N-Methylpyrrolidone On Postnatal
Development And Behaviour In Rats”, Hass U. et al., Neurotoxicol. Teratol.: 1994,
16, (3), 241-249.
Wistar rats were exposed by inhalation to 150ppm NMP for 6 hours/day, daily
from days 7-20 of gestation and were then allowed to litter. No maternal toxicity
was detected and litter size was unaffected by treatment. No physical
abnormalities were described. The offspring were reduced in weight, the
difference being statistically significant up to week 5 after birth. Pre-weaning
development was impaired as was higher cognitive function related to solving of
difficult tasks. Basal function of the CNS was normal and there were no effects on
learning of low grade tasks. A NOEL was not established.

20


150 ppm =

150 x 99.13
= 608.16 mg/m 3 = 0.608 mg/L
24.45


Daily dose =

PDE =

0.608 x 6
= 0.152 mg/L
24

0.152 x 290
= 133.58 mg/kg
0.33

133.58 x 50
= 5.3 mg/day
5 x 10 x 1 x 5 x 5

Limit =

5.3 x 1000
= 530 ppm
10

Conclusion:
This study was chosen because of the toxicity endpoint that was seen, that is, the
effect of the solvent on the function of the developing nervous system in utero.
This is a potentially serious toxicity since we do not know if it is a permanent
effect or if it is reversible. We are not sure if this delayed development could be
due to the lower body weight of the pups. However, the EWG has decided to be
cautious in its interpretation and in its safety decision.
The EWG members thus recommend that N-methylpyrrolidone should be kept in
methylpyrrolidone
Class 2 in Table 2 in the ICH Impurities: Residual Solvents Guideline. A new
PDE and limit as described above should also be declared for this solvent. Class 2
contains those solvents that have significant toxicities such as neurotoxicity, nongenotoxic carcinogenicity, teratogenicity etc., and should be limited in their use up
to the PDE limits listed in the table.

21

PART IV:
IMPURITIES : RESIDUAL SOLVENTS (MAINTENANCE)
PDE FOR CUMENE
Having reached Step 4 of the ICH Process and incorporated into the core Guideline
on 4 February 2011, this Guideline is recommended for

Introduction
Cumene
[synonyms:
Cumol;
isopropylbenzene;
isopropylbenzol;
(1methyl/ethyl)benzene; 2-phenylpropane] is listed in the ICH Q3C guideline in Class
3, i.e., as a solvent with low toxicity. A summary of the toxicity data used by the
EWG to establish a Permitted Daily Exposure (PDE) value for cumene at the time
when the ICH Q3C guideline was signed off at Step 2 in November 1996 is published
in Connelly et al. (1).
According to this report from the EWG no data from carcinogenicity studies with
cumene were available. Regarding genotoxicity data cumene was reported negative in
an Ames test and in Saccaromyces cerevisiae and positive in in vitro UDS and cell
transformation assays using mouse embryo cells. Calculation of a PDE value was
based on a rat toxicity study published in 1956. Female Wistar rats were given
cumene at doses of 154, 462 and 769 mg/kg by gavage 5 days/week for 6 months. No
histopathological changes but slight increases in kidney weights at the two higher
doses were observed suggesting a NOEL of 154 mg/kg. It was concluded that the PDE
for cumene is 55.0 mg/day i.e., cumene is a solvent with low toxicity to be listed in
Class 3. (1)
Meanwhile new toxicity data have been published including results from NTP 2-year
inhalation studies showing that cumene is carcinogenic in rodents. (2) A reappraisal
of the PDE value of cumene according to the maintenance agreement from 1999 is
therefore initiated. For establishing a revised PDE value in this document the
standard approaches (modifying factors, concentration conversion from ppm to mg/L,
values for physiological factors) as described in detail in Connelly et al. (1) were used.
Genotoxicity
Cumene was not mutagenic in S. typhimurium strain TA97, TA98, TA100, or
TA1535, when tested with and without liver S9 activation enzymes. Cumene induced
small, but significant, increases in micronucleated polychromatic erythrocytes in
bone marrow of male rats treated by intraperitoneal injection. In contrast, no
increase in micronucleated erythrocytes was observed in peripheral blood of male (up
to 1000 ppm) or female (up to 500 ppm) mice exposed to cumene by inhalation for 3
months. (2)

p53 and K-ras mutations were found in 52% and 87% of lung neoplasms in exposed
mice compared to 0% and 14% in the chamber controls, respectively. This pattern of
mutations identified in the lung tumors suggests that DNA damage and genomic
instability may be contributing factors to the development of lung cancer in mice. (3)
However, the overall genotoxic profile does not provide sufficient evidence for a direct
mutagenic mode of action of cumene or its metabolites as the primary cause in
tumorigenesis. (2)

22


Carcinogenicity
F344 rats were exposed to concentrations of 250, 500, or 1000 ppm of cumene in air
by inhalation 6h/day, 5 days/week for 2 years. Increased incidences of respiratory
epithelial adenoma in the nose and renal tubule adenoma or carcinoma (combined) in
males at all dose levels. Increased incidences of respiratory epithelium adenoma in
the nose in females at all dose levels. (2)
Molecular weight of cumene: 120.19
LOEL 250 ppm (a NOEL for carcinogenic effects was not established)

250 ppm =

250 x 120.19
= 1229 mg/m³ = 1.23 mg/l
24.45


Daily dose =

1.23 x 6 x 5
= 0.22 mg/l
24 x 7

0.22 mg l -1 x 290 l day -1
= 150 mg/kg/day
0.425 kg

Rat respiratory volume: 290 l day-1
Rat body weight: 0.425 kg

PDE =

150 x 50
= 1.50 mg/day
5 x 10 x 1 x 10 x 10

F1 = 5 to account for extrapolation from rats to humans
F3 = 1 because long duration of treatment (105 weeks)
F4 = 10 because oncogenic effect was reported
F5 = 10 because a NOEL was not established

Limit =

1.5 x 1000
= 150 ppm
10

23


B6C3F1 mice were exposed to concentrations of 125, 250, or 500 ppm (females) or
250, 500, or 1000 ppm (males) of cumene in air by inhalation 6h/day, 5 days/week for
2 years. Increased incidences of alveolar/bronchiolar neoplasms in males and females
at all dose levels. Incidences of hepatocellular adenoma or carcinoma (combined)
showed a dose-related increase in female mice. (2)
LOEL 125 ppm (female mice)

125 ppm =

125 x 120.19
= 614 mg/m³ = 0.61 mg/l
24.45


Daily dose =

0.61 x 6 x 5
= 0.11 mg/l
24 x 7

0.11 mg l -1 x 43 l day -1
= 169 mg/kg/day
0.028 kg

Mouse respiratory volume: 43 l day-1
Mouse body weight: 0.028 kg

PDE =

169 x 50
= 0.70 mg/day
12 x 10 x 1 x 10 x 10

F1 = 12 to account for extrapolation from mice to humans
F3 = 1 because long duration of treatment (105 weeks)
F4 = 10 because oncogenic effect was reported
F5 = 10 because a NOEL was not established

Limit =

0.7 x 1000
= 70 ppm
10

Conclusion
The main carcinogenic effects in the rodent studies can be related to the inhalation
route of administration (respiratory and olfactory tissues) and may therefore not be
relevant for a residual solvent in (mainly) orally applied pharmaceuticals. However,

24


systemic carcinogenic effects were also reported (kidney in male rats, liver in female
mice) and the use of the NTP study data for calculation of a PDE is therefore
considered appropriate.
The former PDE for this solvent was greater than 50 mg/day (55 mg/day) and cumene
was placed in Class 3. The newly calculated PDE for cumene based upon
carcinogenicity data is 0.7 mg/day, therefore, it is recommended that cumene be
placed into Class 2 in Table 2 in the ICH Impurities: Residual Solvents Guideline.
into
References
1. Connelly JC, Hasegawa R, McArdle JV, Tucker ML. ICH Guideline Residual
Solvents. Pharmeuropa (Suppl) 1997;9:57.
2. Toxicology and Carcinogenesis Studies of Cumene (CAS No. 98-82-8) in
F344/N Rats and B6C3F1 Mice (Inhalation Studies). Natl Toxicol Program
Tech Rep Ser 2009;542;NIH 09-5885.
3. Hong HHL, Ton TVT, Kim Y, Wakamatsu N, Clayton NP, Chan PC et al.
Genetic Alterations in K-ras and p53 Cancer Genes in Lung Neoplasms from
B6C3F1 Mice Exposed to Cumene. Toxicol Pathol, 2008;36:720-6.

25

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