1. COMPOUNDING CALCULATIONS Jessica Johnson, Pharm. D.

2. TOPICS Percent Concentrations Ratio Concentrations Determining # of tabs/caps needed to reformulate into a liquid Recipes Enlarging Reducing

3. PERCENT CONCENTRATIONS Units need to ALWAYS be in grams and/or milliliters w/v = weight/volume = grams/mL Used when a solid is mixed into a liquid v/v = volume/volume = mL/mL Used when a liquid is mixed into another liquid w/w = weight/weight = grams/grams Used when a solid is mixed into another solid

4. Example (w/w):

5. Example (w/v):

6. Using the example from the previous page, say that we wanted to know how much liquid we could make from 15 grams of lisinopril. How would that be set up?

7. Practice – Percent Concentrations

8. You need to make a Prevacid solution (w/v) that contains 3% Prevacid. If you are making a total of 35 mL of the solution, how many g of Prevacid should be used?

9. Practice – Percent Concentrations You need to make Ranitidine 4% solution for a patient. If you are making 5 ounces total, how many mg of ranitidine should be used? Hint: Watch your units!

10. Questions?

11. Ratio Concentrations

12. Example:

13. Ratio - Practice You are making a solution (w/v) that is to contain 1:4000 active drug. If you are making a total of 100 mL, how many grams of active drug should be used?

14. Ratio  Percent

15. Ratio  Percent Practice Convert the ratio 1:12,500 (w/v) to a percent.

16. Percent  Ratio

17. Percent  Ratio Practice Convert 0.002% to a ratio

18. Questions?

19. Determining the # of tablets to use for a compound Sometimes, pharmacists and technicians will need to reformulate medication from a tablet or capsule into a liquid We need to know how to determine how many tabs/caps to use

20. Example You are preparing a Prevacid solution that should have the final concentation 30 mg/5 mL. If Prevacid is available as a 15 mg capsules, how many should be used to prepare 100 mL of solution? Two ways to solve: Determine how many mg are in the total solution, and divide by 15 mg Use Dimensional analysis

21. (Space to write from last example)

22. Example: You are preparing 200 mL of a solution that contains 25 mg/10 mL. If tablets are available as 10 mg each, how many should be used to prepare this solution?

23. Example You are making a solution that contains 30 tablets that are 10 mg each. If the final solution contains 150 mL, what is the concentration?

24. Practice You are making a solution that contains 40 mg/5 mL. If you are dispensing a total of 4 ounces, how many 15 mg tablets should be used?

25. Practice You are making a solution that contains 15 tablets that are 20 mg each. If the final solution is 200 mL, what is the concentration (mg/mL)?

26. Questions?

27. Recipes Some of you may end up with a recipe question Think of these as literal recipes, such as used in cooking, to make things easier Example recipe: Diaper Paste triamcinolone 3 grams nystatin 4 grams Eucerin qs 35 grams

28. Recipes Diaper Paste triamcinolone 3 grams nystatin 4 grams Eucerin qs 35 grams How many grams does this recipe make? What do you think we do if we only have this recipe available, but need to make 50 grams? Enlarge it!

29. Recipes

30. Do we need to calculate the amount of Eucerin needed for the new recipe? NO: Remember that qs means “quantity sufficient” Therefore, after the Triamcinolone and Nystatin have been mixed together, we would add ENOUGH Eucerin to make the final compound 50 grams Why might the amount of Eucerin added vary slightly each time this compound is made?

31. Recipe Practice Using the same idea, REDUCE the following recipe to determine how much of each ingredient would be needed to prepare 120 mL of the compound. Recipe: Magic Mouthwash Benadryl 30 mL Maalox 30 mL Viscous lidocaine 30 mL Total volume: 90 mL

32. Recipes Practice Enlarge the following recipe to calculate the amount of each ingredient needed to make 450 grams Ibuprofen Cream Ibuprofen powder 4 grams Capsaicin 0.5 grams Eucerin Cream qs 30 grams

33. Questions?

34. Practice: