Calcul-Part.ppt
- 1. Calculation of Doses • Prime responsibility of a pharmacist is to check the doses specified in the prescription. • He or she is ethically bound to consult the physician if he feels so or come across an unusual dose • Normally pharmacist and a physician accept the capacity of 4ml as a teaspoon. • However, certain factors such as, viscosity and surface tension of a given liquid will influence the actual volume delivered by a teaspoon
- 2. Table of Approximate Equivalents Household Measure Metric Measure Apothecaries Measure 1 teaspoonful 5ml 4/3 fluid-drachm 1 dessertspoonful 10ml 8/3 fluid-drachm 1 tablespoonful 15ml 4 fluid drachm I wineglassful 60ml 2 fluid ounce
- 3. Calibration of Droppers • A dropper may be calibrated by counting the drops of a liquid as they fall into a graduate until a measurable volume is obtained. • The volume of the drop is then calculated in terms of a defined unit e.g. ml • United states pharmacopoeia defines the official medicine dropper as being constricted at the delivery end to a round opening having an external diameter of 3 mm
- 4. Equivalents – approx. or exact • All doses in United state pharmacopoeia and National formulary are in metric system. • Therefore, it’s the responsibility of a Pharmacist to ensure approx or exact equivalents in apotheracaries system with reference to the ‘Table of Metric Doses with Approximate Apothecary Equivalents’ • Approx. dose equivalents cannot be used for the conversion of specific quantities which requires compounding – for such exact equivalents should be used and are to be rounded to 3 significant figures.
- 5. • How many 20 minim doses are contained in 40 ml of liquid • 40 ml = 40 x 16.23 m = 649.2 m • Number of does 649.2 (m) = • 20 (m) • If a table spoon is prescribed as the does of a medicine, appprox. How many doses will be contained in 12 fluidounces • 1 tablespoon = 4 fluiddrachm • 12 fluid ounce = 96 fluid drachm • Number of does = 96 = • 4 32 doses 24 doses
- 6. Calculate the number of doses in a specified amount of medicine • Number of doses = Total amount / Size of dose • Total amount and the dose must be measured in a common denomination • Example • If the dose of a drug is 200 milligrams, how many doses are contained in 10 grams? • 10 g = 10000 mg • Number of doses = 10000 (mg) = 50 doses. answer • 200 (mg)
- 7. Calculate the size of each dose • Size of dose = Total amount • Number of doses • Example • How many drops would be prescribed in each does of a medicine if 15 ml contain 60 doses • Dispensing dropper calibrates 32 drops per ml • 15 ml = 15 x 32 = 480 drops • Size of dose = 480 = 8 drops. Answer • 60
- 8. To calculate the amount of medicine • Total amount = number of doses x size of dose • Example: • How many ml of a medicine would provide a patient with a 2 tablespoon twice a day for 8 days • Number of doses = 16 • Size of dose = 2 tablespoons or 30ml • Total amount = 16 x 30 = 480 ml. answer
- 9. • How many milligrams of a drug will be needed to prepare 72 dosage forms if each is to contain 1/12 grain • Number of doses = • Size of dose = 1/12 = • Total amount of medicine = 72 x 5.4 = 72 5.4 mg 390 mg. answer
- 10. To calculate the quantity of an ingredient in each specified dose • When the number of doses in a total amount is given • Quantity in each dose = Quantity in total amount • Number of doses • But when the number of doses is not given then more convenient is to use this • Total amount = Quantity of ingredient in total • Size of dose x • X = quantity in each dose
- 11. • Examples • If 0.050 g. of a substance is used in preparing 125 tablets, how many micrograms are represented in each tablet • 0.050 g. = 50 mg = 5000 ug • 5000 / 125 = • If a preparation contains 5 g. of a drug in 500ml., how many grams are contained in each tablespoonful dose. • 1 tablespoon = 15 ml • 500 (ml) = 5 (g) • 15 (ml) x • X = 0.15 g. answer 400ug. answer
- 12. Calculate the quantity of an ingredient in a specified total amount of medicine • When the number of doses is known • Quantity in total = Quantity in dose x Number of doses • Otherwise • Size of dose = Quantity of ingredient in each dose • Total amount x
- 13. • Examples: • How many grams of a chemical are required to make 120 ml of a solution each of teaspoon of which will contain 3mg of the chemical • 1 teaspoon = 5ml • 5 (ml) = 3 (mg) • 120 (ml) x (mg) • X = 72 mg. answer
- 14. Calculate the dose of a drug, given the amount per kilo of body weight • Example • The dose of a drug is 1/10 grain per kilo of body weight. How many milligrams should be given to a person weighing 154 lb. • 1/10 gr. = 6.5 mg • 1 Kilo = 2.2 lb. • 2.2 (lb) = 6.5 (mg) • 154 (lb) x (mg) • X = 455 mg. answer
- 15. Calculation of dose for children • Most commonly used method is known as Young’s rule • Divide the age of the child by age plus 12 and multiply by the adult dose • Age x Adult dose = Dose for child • Age + 12 • Example • If the adult dose of a drug is 5mg, what is the dose for a child 8 years old • 8 x 5mg = 2/5 x 5 = 2 mg. answer • 8 + 12
- 16. Other Methods • Cowling’s Rule • Age at next birthday (in years) x Adult dose = Dose for child • 24 • Fried’s Rule for Infants • Age (in months) x Adult dose = Dose for child • 150 • Clark’s Rule • Weight (in pounds) x Adult dose = Dose for child • 150
- 17. Calculate dose for children on a basis of surface area as related to weight • Today many physician believe that doses for children should be based upon body surface area • Since the correct dosage of drugs seems more nearly proportional to the surface area. Reference Table by Crawford, Jhon, D. et al., 1950 Kilograms Pounds Square meters Percent of Adult dose 2 4.4 0.12 6 5 11 0.25 13 10 22 0.44 22 20 44 0.79 40 30 66 1.07 51 50 110 1.53 75
- 18. Practice problems • If the dose of a drug is 150 microgrmas, how many doses are contained in 0.120 g. ? • A medicine is to be taken in 5-minim doses. How many doses are contained in 15ml of the medicine. • What is the doses in teaspoonfuls if 500 ml of a medicine contain 50 doses. • If 240 ml of a liquid contain 0.120 g. of a chemical and 2 teaspoonful are taken at a dose, how many grains will each dose contain? • 240 = 120 (mg) = • 10 x = 0.120 x 1000,000 = 120000 / 150 = 800 doses = 15 x 16.23 = 243.45 / 5 = 48 doses = 500 / 50 = 10 / 5 = 2 teaspoonful 1/13 grains., answer
- 19. Practice problems • The adult dose of a liquid medication is 1 ml. per 10 kilograms body weight to be administered in a single dose. How many teaspoonfuls should be administered to a person weighing 220lb. ? • 22 (lb) = 1 (ml) = • 220 (lb) x • If the usual adult dose of a drug is 0.10 g., what is the dose for a child 4 years old? • Age x Adult dose = Dose for child • Age + 12 • 4 x 100 (mg) = • 4 + 12 220 / 22 = 10 ml = 2 teaspoonfuls = 25mg. Or 0.025 g. answer
- 20. Reducing and Enlarging Formulas • In dispensing, pharmacist may have to reduce and enlarge official formulas in manufacturing. • Official formulas may have quantities of 1000ml or 1000g • Whereas prescriptions may have small quantities such as 30 ml of 30 g. • For quantity manufacturing there may require large quantities such as, 5 gallons or 25 pounds.
- 21. • When a formula specifies a total amount, then one may determine how much of each ingredient is needed to obtain a desired amount • Total amount specified in frmla = Quantity of each ingredient in frmla • Total amount desired X • X = Quantity of each ingredient in amount desired
- 22. • However, all problems can be solved by this proportion • But it is more convenient to solve them by use of shortcuts • For example, if we want to prepare 1 gallon (3785 ml) of a formula whose official amount is 1000ml then • We simply multiply each ingredient by the factor 3.785
- 23. • Fro example if we have official amount of 1000 ml or 1000 g we may multiply or divide by power of 10 by moving decimal point to the right or left. • However, some formulas do not specify a total amount rather indicate relative quantities of each ingredient or proportion parts
- 24. • Such problems may be solved by this proportion • Total number of parts in formula = Total amount desired • Number of parts of each ingredient X • X = Quantity of each ingredient in amount desired
- 25. • In solving problems – reducing of enlarging formulas, some facts should be taken into consideration • 1. To make a valid ratio – total amounts compared must be expressed in a common denomination. • If they are not then one must be reduced or converted to common denomination • For example: if formula is given in metric system and the required quantity is in common system then it is best to convert the required quantity in metric system
- 26. • 2. As quantity of each ingredient is calculated separately, it does not matter if the formula includes an assortment terms (pounds and fluidounces, grams and milliliters)
- 27. Formulas that specify amounts of ingredients • Example: • Calamine 80g • Zinc Oxide 80g • Glycerine 20ml • Bentonite Magma 250ml • Lime water, to make 1000ml • Calculate the quantity of each ingredient required to make 240 ml of Calamine lotion
- 28. • Use factor 0.24 – because 0.24 x 1000 = 240 or 240 / 1000 = 0.24 • Calamine = 80 x 0.24 = 19.2 g • Zinc oxide = 80 x 0.24 = 19.2 • Glycerine = 20 x 0.24 = 4.8 ml • Bentonite Magma = 250 x 0.24 = 60 ml • Lime water, to make 240 ml
- 29. • Example. 2 • Benzoin 100g • Aloe 20g • Storax 80g • Tolu Balsam 40g • Alcohol to make 1000ml • We have to make it for I gallon (1 gallon = 3785 ml)
- 30. • So using factor 3.785 since, 1000ml x 3.785 = 3785 ml • Benzoin = 100 x 3.785 = 378.5g • Aloe = 20 x 3.785 = 75.7g • Storax = 80 x 3.785 = 302.8g • Tolu Balsam = 40 x 3.785 = 151.4g • Alcohol to make 1 gallon
- 31. • Example 3 • Belladonna Extract 1.0g • Ephedrine Sulphate 1.6g • Phenobarbital 2.0g • Aspirin 32.0g • We have to make each ingredients for 24 capsules since this formula is for 100 capsules
- 32. • Using factor 0.24 – since 0.24 x 100 = 24 or 24 / 100 = 0.24 • Belladonna Extract 1.0 x 0.24 = 0.24g • Ephedrine Extract 1.6 x 0.24 = 0.384g • Phenobarbital 2.0 x 0.24 = 0.48g • Aspirin 32.0 x 0.24 = 7.68g
- 33. Formulas that specify proportional parts • some facts about proportional parts • 1. when parts by weight are specified, we can convert only to weights and not to volumes – same goes for parts by volume • 2. Our calculations will always result in single denominations
- 34. • Examples • Calculate the quantity of each ingredient required to make 1000 g. of the ointment • Cade Oil 5 parts • Zinc Oxide 10 parts • Hydrophilic Ointment 50 parts • Total number of parts = 65 • Means 1000 g. will contain 65 parts
- 35. • Cade Oil 5 parts • 65 (parts) = 1000 (g) • 5 (parts) X (g) • = 65X = 5000 = 5000 / 65 • X = 76.92 g. of Cade Oil
- 36. • Zinc Oxide 10 parts • 65 (parts) = 1000 (g) • 10 (parts) Y (g) • = 65Y = 10,000 = 10,000 / 65 • Y = 153.85 g. of Zinc Oxide
- 37. • Hydrophilic Ointment 50 parts • 65 (parts) = 1000 (g) • 50 (parts) Z (g) • = 65Z = 50,000 = 50,000 / 65 • = Z = 769.23 g. of Hydrophilic Ointment
- 38. • Calculate the quantity of each ingredient required to make 5 lb. of the powder • Bismuth Sub-carbonate 8 parts • Kaolin 15 parts • Magnesium Oxide 2 parts • Total number of parts 25 parts • 5lb. (454 g. x 5) or 2270 g. will contain 25 parts
- 39. • Bismuth Subcarbonate 8 parts • 25 (parts) = 2270 (g) • 8 (parts) X (g) • = 25X = 18160 = 18160 / 25 • X = 726.4 g. of Bismuth Sub-carbonate
- 40. • Kaolin 15 parts • 25 (parts) = 2270 (g) • 15 (parts) Y (g) • = 25Y = 34050 = 34050 / 25 • Y = 1362 g. of Kaolin
- 41. • Magnesium Oxide 2 parts • 25 (parts) = 2270 (g) • 2 (parts) Z (g) • = 25Z = 4540 = 4540 / 25 • Z = 181.6 g. of Magnesium Oxide
- 42. Calculate the quantities of ingredients in a desired amount when proportional parts may be reckoned from the formula • If ingredients are all measured by weight or volume • We may consider the sum of the weights (or volumes) when expressed in a common denominations as total number of parts
- 43. • Example • Calculate the quantity of each ingredient required to make 500g. Of the powder • Boric Acid 5 g • Starch 20 g • Talc 50 g • Total number of parts = 75 • So 500 g will contain 75 parts
- 44. • For Boric Acid • 75 (parts) = 500 (g) • 5 (parts) X (g) • X = 33.3 g. of Boric Acid
- 45. • For Starch • 75 (parts) = 500 (g) • 20 (parts) Y (g) • Y = 133.3 g. of Starch
- 46. • For Talc • 75 (parts) = 500 (g) • 50 (parts) Z (g) • Z = 333.3 g. of Talc
- 47. Practice Problems • Calculate the quantities required to make 180 ml of Benzyl Benzoate Lotion • Benzyl Benzoate 250 ml • Tri-ethanolamine 5 g • Oleic acid 20 g • Purified water, to make 1000ml Factor = 0.18
- 48. Problem - 2 • Calculate the quantities required to make 5 gallons of a Camphor and Soap Liniment • Green Saop 120 g • Camphor 45 g • Rosemary Oil 10 ml • Alcohol 700 ml • Purified Water, to make 1000 ml Factor = 3.785
- 49. Problem - 3 • Calculate the quantity of each ingredient required to make 10 lb. of Green Soap. 10lb = 4540 g • Vegetable Oil 380 g • Oleic acid 20 g • Potassium hydroxide 91.7 g • Glycerin 50 ml • Purified water, to make 1000 g Factor = 4.54
- 50. Problem - 4 • Calculate the quantity of each ingredient required to make 1500 g. of the powder • Calcium Carbonate 5 parts • Magnesium Oxide 1 part • Sodium Bi-coarbonate 4 parts • Bismuth Sub-carbonate 3 parts 13 (parts) = 1500 (g) 5 (parts) X (g)
- 51. Problem - 5 • How much of each ingredient should be used to prepare 5 lb. of the following ointment • Stearic Acid 14 g • Tri-ethanolamine 1 g • Cetyl Alcohol 4 g • Glycerin 8 g • Water 63 g Total parts = 90 5lb = 2270 g 90 (parts) = 2270 (g) 14 (parts) X (g)
- 52. Density, Specific Gravity and specific Volume • Density: mass per unit volume – g/ml • Specific Gravity: is a ratio of weight of a substance to the weight of an equal volume of a substance chosen as a standard – both having same temperature • Water is used as the standard for the specific gravities of liquids and solids • While most useful standard for gases is hydrogen
- 53. • According to United state pharmacopoeia the standard temperature for specific gravities • is 25 degree Celsius and for • alcohol is 15.56 degree Celsius
- 54. How to Calculate the specific gravity of a liquid when its weight and volume are known • Example • If 54.96 ml of an oil weigh 52.78 g, what is the specific gravity of the oil • 54.96 ml of water weigh 54.96 g. • Specific gravity of Oil = 52.78 / 54.96 • Sp. Gr = 0.9603, answer
- 55. How to calculate the specific gravity of a liquid, determined with a specific gravity bottle • First weigh the empty Sp. Gravity bottle • Weigh the container first filled with water and then with the liquid. • By subtracting the weight of the empty container we get the weights of the equal volumes.
- 56. • Example • A specific gravity bottle weighs 23.66 g. When filled with water it weighs 72.95 g. when filled with another liquid it weighs 73.56 g. What is the specific gravity of the liquid? • Weight of liquid = 73.56 – 23.66 = 49.90 g. • Weight of water = 72.95 – 23.66 = 49.29 g. • Specific gravity of Liquid = 49.90 / 40.29 = 1.0123. Answer
- 57. Calculate the Sp. Gravity of a liquid determined by displacement method or Plummet method • Determination based on Archimedes's principle – that a body immersed in a liquid displaces an amount of the liquid equal to its own volume and suffers an apparent loss in weight equal to the weight of the displaced liquid.
- 58. • Example • A glass plummet weights 12.64 g. in air, 8.57 g. When immersed in water and 9.12 g. when immersed in an oil. Calculate the specific gravity of the oil • Oil displacement = 12.64 – 9.12 = 3.52 • Water displacement = 12.64 – 8.57 = 4.07 • Specific Gravity of Oil = 3.52 / 4.07 = 0.865, answer