pharmaceutical calculations for the pharmacy technician copyright © 2008 wolters kluwer health |...
TRANSCRIPT
![Page 1: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/1.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 10
Dilution and Concentration
![Page 2: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/2.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Objectives
• Upon completion of this chapter, you will be able to:
– Describe the relationship of active ingredients and diluents if the amount of active ingredient remains constant and the amount of diluent is increased or decreased
– Determine the percent strength and ratio strength of a given product when the active ingredient remains constant and the amount of diluent is increased or decreased
![Page 3: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/3.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Objectives (cont.)
– Determine the volume of solution of a desired strength given a specified quantity of any given strength
– Determine the volume of a specified stock solution needed to prepare a given solution
– Determine the quantity of an active ingredient in a specified amount of solution needed to prepare a given solution
– Define the alligation methods of problem solving
![Page 4: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/4.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Objectives (cont.)
– Utilize the alligation methods (alligation alternate and alligation medial) to determine the percent strength of alcohol mixtures
– Utilize the alligation methods (alligation alternate and alligation medial) to determine relative amounts of components mixed together to make a mixture of a required strength
![Page 5: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/5.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Definitions
• Diluent:– A substance that is added to a
pharmaceutical product to reduce the strength of the product. A diluent most often has no drug substance in it, sterile water and petrolatum for example.
• Stock solutions:– Strong solutions from which weaker ones are
made
![Page 6: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/6.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Rules
These two rules, wherever they may be applied, greatly simplify the calculation:
• 1. When ratio strengths are given, convert them to percentage strengths before setting up a proportion
• 2. Whenever proportional parts enter into a calculation, reduce them to lowest terms
them to percentage strengths before setting up a proportion
calculation, reduce them to lowest terms
![Page 7: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/7.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Relationship Between Strength and Quantity
• The amount of active ingredient remains constant; any change in the quantity of a solution or mixture of solids is inversely proportional to the percentage or ratio strength. (Or, as the volume increases the strength decreases.)
![Page 8: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/8.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Methods of Problem Solving
• 1. Inverse proportion
• 2. The equation:
Q1 (C1) = Q2 (C2)
• 3. By determining the quantity of active constituent (solute) needed and then calculating the quantity of the available solution (usually concentrated or stock solution) that will provide the needed amount of constituent
![Page 9: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/9.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Which one to use?
• For most problems, the equation (#2) is the easiest to use
• In some situations, when using vials or amps as your stock product, #3 would be the best method
![Page 10: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/10.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Dilutions and Concentrations of Liquids• Example
– If 500 mL of a 15% (v/v) solution of methyl salicylate in alcohol are diluted to 1500 mL, what will be the percentage strength (v/v)?
• Q1 (C1) = Q2 (C2)
500 mL (15 %) = (1500 mL) (X %)
X = 5% (answer)
![Page 11: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/11.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example
• If 50 mL of a 1:20 (w/v) solution of aluminum acetate are diluted to 1000 mL, what is the ratio strength (w/v)?
• Use same formula
(50 mL) (5 %) = 1000 mL (X %)
X = 0.25% = 1:400 (answer)
![Page 12: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/12.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Determine Amount of Solution of a Desired Strength• How many grams of 10% (w/w)
ammonia solution can be made from 1800 g of 28% (w/w) strong ammonia solution?
• Use the same formula
(1800 g)(28 %) = (X g) (10%)
X = 5040 g (answer)
![Page 13: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/13.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example
• How many milliliters of a 1:5000 (w/v) solution of phenylmercuric acetate can be made from 125 mL of a 0.2% solution?
• 1:5000 = 0.02%
• Use the same formula
(125 mL) (0.2 %) =(X mL) (0.02 %)
X = 1250 mL (answer)
![Page 14: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/14.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How many milliliters of a 1:400 (w/v) stock
solution should be used to make 4 liters of a 1:2000 (w/v) solution?
• 4 liters = 4000 mL
• 1:400 = 0.25% 1:2000 = 0.05%
• Use the same formula
X mL (0.25 %) = 4000 mL (0.05%)
X = 800 mL (answer)
![Page 15: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/15.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How many milliliters of a 1:400 (w/v)
stock solution should be used in preparing 1 gallon of a 1:2000 (w/v) solution?
• 1 gallon = 3785 mL
• 1:400 = 0.25% 1:2000 = 0.05%
X (0.25%) = (3785 mL)(0.05%)
X = 757 mL (answer)
![Page 16: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/16.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Using a Vial or Amp Stock
• We are to prepare 30 mL of a 5 mg/mL oral phenobarbital solution using 1 mL vials with a concentration of 65 mg/mL. How much stock solution will be required?
![Page 17: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/17.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Step 1:
• Calculate the amount of phenobarbital needed
– 30 ml x 5 mg/mL tells us we need 150 mg of phenobarbital for the solution
![Page 18: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/18.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Step 2:
• Calculate the volume of available stock needed. Our supply is 65 mg/mL, so
65 mg = 150 mg 1 mL X
X = 2.3 mL of phenobarbital will have to be drawn up
![Page 19: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/19.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
In order to use our formula we must calculate the percent strength of each ingredient5 mg/mL = 0.005 g/mL which is a 0.5% solution65 mg/mL = 0.065 g/mL = 6.5% solutionX (6.5%) = (30 mL) (0.5%)X = 2.3 ml of phenobarbital required (answer)
• In order to use our formula we must calculate the percent strength of each ingredient
• 5 mg/mL = 0.005 g/mL which is a 0.5% solution
• 65 mg/mL = 0.065 g/mL = 6.5% solution
X (6.5%) = (30 mL) (0.5%)
X = 2.3 ml of phenobarbital required (answer)
![Page 20: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/20.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Determining Quantity of Active Ingredient in Specified Amount of Solution Given Strength of Diluted Portion
![Page 21: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/21.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How much silver nitrate should be used
in preparing 50 mL of a solution such that 5 mL diluted to 500 mL will yield a 1:1000 solution?
1000 mL = 1 g 500 mL X g
– X = 0.5 g of silver nitrate in 500 mL of diluted solution (1:1000), which is also the amount in 5 mL of the stronger (stock) solution, since the 50 mL and the 5 mL are the same strength
![Page 22: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/22.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
5 mL = 0.5 g 50 mL X g
X = 5 g (answer)
![Page 23: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/23.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Amount of Diluent Needed for Preparing Solution of Specified Lower Strength
![Page 24: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/24.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How many milliliters of water should be
added to 300 mL of a 1:750 (w/v) solution of benzalkonium chloride to make a 1:2500 (w/v) solution?
– 1:750 = 0.133% 1:2500 = 0.04%
– Using our formula, recall that the Q2 always represents the FINAL volume
– (300 mL) (0.133%) = X (0.04%)
– X = 997.5 or 1000 mL
![Page 25: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/25.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
– This is the volume of our 0.04% solution; therefore, we must subtract the volume of the 0.133% solution (the amount we started with) from this final volume to determine how much water or diluent was added.
1000 mL – 300 mL = 700 mL (answer)
![Page 26: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/26.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Alligation
• Arithmetical method of solving problems that involves mixing of solutions or solids that have different percentage strengths
![Page 27: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/27.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Alligation Medial
• Uses the weighted average
• Used when the percent strength of each component is KNOWN
• Express the percent strength by a decimal fraction
• Multiply the decimal by the corresponding quantity
• Add the products and divide by the total quantity of the mixture
![Page 28: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/28.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example
• What is the percent strength of a product that is made up of 3000 mL of 40% alcohol, 1000 mL of 60% alcohol and 1000 mL of 70% alcohol?
– 40% = 0.4 x 3000 mL = 1200 mL
– 60% = 0.6 x 1000 mL = 600 mL
– 70% = 0.7 x 1000 mL = 700 mL
– Add total volume = 5000 mL
![Page 29: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/29.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
– Add the products 1200 mL + 600 mL + 700 mL = 2500 mL
– Divide 2500 mL by 5000 mL = 0.5 (change this to a percent) x 100 = 50%
– Therefore by mixing these products the final product is 5000 mL of a 50% alcohol product
![Page 30: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/30.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Alligation Alternate• This method calculates the number of
PARTS of two or more components of a certain strength. The final proportion allows us to use proportional parts to make any amount of the product we wish.
• Strength of the final product must be in-between the strengths of the components we are mixing
![Page 31: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/31.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example
• Mix a 95% product with a 50% product to get a 70% product
– Subtract 70 from 95 and get 25
– Subtract 50 from 70 and get 20
– Now we have 20 parts of 95% and 25 parts of 50%
– Remember to REDUCE 20:25 = 4:5
![Page 32: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/32.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
![Page 33: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/33.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
– So if we mix 4 parts of 95% and 5 parts of 50% we will get a 70% product
– We can apply this to liquids or solids
– Say we need 1 pound of a 70% coal tar product, how much of 95% and how much of 50% will we need?
4 = X 9 454 grams
![Page 34: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/34.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
– The final product is 1 pound or 454 grams that is represented by 9 total parts (4 + 5)
– Solve for X and 201.7 grams of 95%
– 454 - 201.7 = 252.3 grams of 50%
![Page 35: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/35.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Using Alligation Alternate When the Quantity of One Ingredient Is Known
![Page 36: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/36.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How many grams of 2.5%
hydrocortisone cream should be mixed with 360 g of 0.25% cream to make a 1% hydrocortisone cream?
2.5% 0.75 part of 2.5% cream
1%
0.25% 1.5 parts of 0.25% cream
Relative amounts: 0.75:1.5, or 1:2
![Page 37: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/37.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
2 parts = 360 g 1 part X g
X = 180 g (answer)
![Page 38: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/38.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example• How many grams of white petrolatum
should be mixed with 250 g of 5% and 750 g of 15% sulfur ointments to prepare a 10% ointment?
12.5% 10 parts of 12.5% mixture
10%
0% 2.5 parts of white petrolatum
Relative amounts: 10:2.5, or 4:1
![Page 39: Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 10 Dilution and](https://reader035.vdocument.in/reader035/viewer/2022081504/56649cf45503460f949c1b8d/html5/thumbnails/39.jpg)
Pharmaceutical Calculations for the Pharmacy Technician Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
Example (cont.)
4 parts = 1000 g 1 part X g
X = 250 g (answer)