Calculating the Amount of Drug in 2 oz of Cream

To determine how muchdrug (active ingredient)is in2 oz (ounces) of cream, we use the given ratio and perform unit conversions.

120 gof cream contains3 gof drug.

2 ozof cream =2 × 28.35 g(since1 oz = 28.35 g)

2 oz = 56.7 g

Step 1: Identify Given DataStep 2: Set Up a Proportion3 g drug120 g cream=x g drug56.7 g cream\frac{3 \text{ g drug}}{120 \text{ g cream}} = \frac{x \text{ g drug}}{56.7 \text{ g cream}}120 g cream3 g drug​=56.7 g creamx g drug​

Step 3: Solve forxxxx=3×56.7120=170.1120=1.42≈1.5 gx = \frac{3 \times 56.7}{120} = \frac{170.1}{120} = 1.42 \approx 1.5 \text{ g}x=1203×56.7​=120170.1​=1.42≈1.5 g

Thus,1.5 g of drugis present in2 oz of cream.

B. 6 g→ Incorrect; this would assume a higher drug concentration.

C. 15 g→ Incorrect; this is a miscalculation of the ratio.

D. 60 g→ Incorrect; far exceeds the total weight of the cream.

Other Answer Choices Explained:References:

PTCB PTCE Exam Content Outline (Pharmaceutical Calculations – Ratios and Proportions)

United States Pharmacopeia (USP) General Chapters on Compounding

The Pharmacy Technician’s Pocket Drug Reference