CETP Pharmaceutical Calculations 3

Question 1

A 250 mg vancomycin dose is prepared in 250 mL of NS and must infuse over 90 minutes. What is the required infusion rate in mL/hr?

Accepted Answer

166.7 mL/hr

Answer

250 mL ÷ (90 min ÷ 60 min/hr) = 250 ÷ 1.5 = 166.7 mL/hr.

Question 2

Calculate the osmolarity of a solution containing 154 mEq/L of sodium and 154 mEq/L of chloride.

Accepted Answer

308 mOsm/L

Answer

Total osmolarity = sum of all dissolved particles = 154 + 154 = 308 mOsm/L (equivalent to 0.9% NaCl).

Question 3

A prescription requires hydrocortisone 2.5% cream, 60 g. How many grams of hydrocortisone active ingredient are needed to prepare this compound?

Accepted Answer

1.5 g

Answer

2.5% w/w of 60 g = 0.025 × 60 = 1.5 g of hydrocortisone.

Question 4

A patient has a GFR of 30 mL/min. A drug is normally dosed at 500 mg every 8 hours for patients with normal renal function (GFR ≥ 90 mL/min). Using proportional dose reduction, what is the renally adjusted dose?

Accepted Answer

167 mg every 8 hours

Answer

Adjusted dose = (patient GFR ÷ normal GFR) × normal dose = (30 ÷ 90) × 500 = 167 mg.

Question 5

How many mL of a 1:1000 epinephrine solution must be drawn up to administer a 0.5 mg dose?

Accepted Answer

0.5 mL

Answer

1:1000 = 1 mg/mL; 0.5 mg ÷ 1 mg/mL = 0.5 mL.

Canadian Entry To Practice

Canadian Entry To Practice

CETP Pharmaceutical Calculations 3