NMC CBT Drug Calculations and Numeracy 3

Question 1

Heparin 25,000 units in 50 mL NaCl to run at 1,200 units/hour. What rate should the syringe pump be set to?

Accepted Answer

2.4 mL/hr

Answer

Concentration = 25000/50 = 500 units/mL. Rate = 1200/500 = 2.4 mL/hr.

Question 2

Prescription: digoxin 125 micrograms daily. Available: 0.25 mg tablets. How many tablets?

Accepted Answer

0.5 tablets

Answer

Convert: 0.25 mg = 250 mcg. Calculate: 125/250 = 0.5 tablet (half).

Question 3

An insulin infusion of 50 units Actrapid in 50 mL NaCl runs at 4 mL/hr. How many units per hour?

Accepted Answer

4 units/hr

Answer

Concentration = 50/50 = 1 unit/mL. At 4 mL/hr: 4 x 1 = 4 units/hr.

Question 4

An 80 kg patient needs gentamicin 5 mg/kg. Available: 80 mg in 2 mL ampoules. How many mL needed?

Accepted Answer

10 mL

Answer

Dose = 5 x 80 = 400 mg. Concentration = 80/2 = 40 mg/mL. Volume = 400/40 = 10 mL (5 ampoules).

Question 5

Prepare adrenaline infusion: 5 mg in 500 mL NaCl. What is the concentration in micrograms per mL?

Accepted Answer

10 mcg/mL

Answer

5 mg = 5000 mcg. Concentration = 5000/500 = 10 mcg/mL.

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