Alligation /Alternate

1. Alligation/Alternate Purpose: An easy method to make a new strength from two existing strengths

2. Triamcinolone cream is available in strengths of 0.1% and 0.5%. What quantity of 0.1% and 0.5% cream is needed to make 100 grams of 0.2% triamcinolone cream? Sample Problem

3. % strength starting material #2 minus % strength desired (absolute value) % strength starting Material #1 0.1 0.3 % strength desired (final product) 0.2 % strength starting material #1 minus % strength desired (absolute value) % strength starting Material #2 Basic Set Up 0.1 0.5

4. % strength starting material #2 minus % strength desired (absolute value) Value is the # of parts needed of starting material #1 0.3 0.3 Value is the # of parts needed of starting material #2 % strength starting material #1 minus % strength desired (absolute value) 0.1 0.1 Total # of parts needed 0.4

5. 0.3 0.4 0.75 Value is the # of parts needed of starting material #1 Total # of parts needed Ratio needed for starting material #1 0.1 0.4 0.25 Value is the # of parts needed of starting material #2 Total # of parts needed Ratio needed for starting material #2

6. 75 grams 0.1% cream 0.75 100 grams Ratio needed for starting material #1 Final amount of product desired Amount needed of starting material #1 25 grams 0.5% cream 0.25 100 grams Ratio needed for starting material #2 Final amount of product desired Amount needed of starting material #2

7. 75 grams 0.1% cream 25 grams 0.5% cream 100 grams 0.2% cream Answer

8. How much of a 20% hydrocortisone (HC) cream and how much of a 5% HC cream would be needed to make 50 grams of a 9% HC cream? Example Problem

9. 20% 4 parts 9% 5% 11 parts Basic Set Up

10. 4 parts 4 parts 11 parts 11 parts 15 parts

11. 4 parts 15 parts 0.267 11 parts 15 parts 0.733

12. 0.267 50 grams 13.3 grams 0.733 50 grams 36.7 grams

13. 13.3 grams of 20% HC cream 36.7 grams of 5% HC cream 50 grams of 9% HC cream

14. Created by: Jeff Sundell & Doug White