PTCE Dosage Calculations 2

Question 1

A patient weighs 154 lbs. A drug is dosed at 5 mg/kg/day divided into 2 equal doses. How many mg per dose?

Accepted Answer

175 mg

Answer

154 lbs ÷ 2.2 = 70 kg; 70 × 5 = 350 mg/day ÷ 2 doses = 175 mg per dose.

Question 2

A vial contains 250 mg/5 mL. The order is for 375 mg. How many mL should be administered?

Accepted Answer

7.5 mL

Answer

375 mg ÷ (250 mg/5 mL) = 375 × 5/250 = 7.5 mL.

Question 3

An IV infusion of 1,000 mL must run over 8 hours. What is the flow rate in mL/hr?

Accepted Answer

125 mL/hr

Answer

1,000 mL ÷ 8 hours = 125 mL/hr.

Question 4

A physician orders amoxicillin 40 mg/kg/day in 3 divided doses for a 33-lb child. The suspension is 125 mg/5 mL. How many mL per dose?

Accepted Answer

6 mL

Answer

33 ÷ 2.2 = 15 kg; 15 × 40 = 600 mg/day ÷ 3 = 200 mg/dose; 200 ÷ (125/5) = 8 mL — wait, 200/25 = 8 mL.

Question 5

A heparin infusion is ordered at 1,200 units/hr. The bag contains 25,000 units in 250 mL. What rate (mL/hr) should the pump be set to?

Accepted Answer

12 mL/hr

Answer

Concentration = 25,000/250 = 100 units/mL; 1,200 ÷ 100 = 12 mL/hr.

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