Pharmacy Dosage Calculations 3

Question 1

A patient weighs 88 kg and is prescribed 5 mg/kg/day of a medication divided into two doses. What is each dose in mg?

Accepted Answer

220 mg

Answer

Daily dose: 88 kg × 5 mg/kg = 440 mg/day. Each dose: 440 ÷ 2 = 220 mg.

Question 2

How many grams of dextrose are in 500 mL of D5W (5% dextrose in water)?

Accepted Answer

25 g

Answer

5% means 5 g per 100 mL. In 500 mL: 5 g/100 mL × 500 mL = 25 g.

Question 3

A prescription reads: metformin 1,000 mg PO BID × 30 days. How many tablets of 500 mg strength are needed to fill this prescription?

Accepted Answer

120 tablets

Answer

1,000 mg ÷ 500 mg/tab = 2 tabs per dose. BID = 2 doses/day. 2 × 2 × 30 = 120 tablets.

Question 4

An ointment requires 3% salicylic acid. The pharmacy has 6% and 1% preparations. Using alligation, what ratio of 6% to 1% is needed?

Accepted Answer

2:3

Answer

Alligation: higher (6%) – desired (3%) = 3 parts of lower; desired (3%) – lower (1%) = 2 parts of higher. Ratio 6%:1% = 2:3.

Question 5

Convert 2.5 tablespoons to mL. (1 tablespoon = 15 mL)

Accepted Answer

37.5 mL

Answer

2.5 tbsp × 15 mL/tbsp = 37.5 mL.

Pharmacy Practice Test