A patient weighing 70 kg is prescribed heparin 12 units/kg/hr. The heparin solution is 25,000 units in 250 mL. What is the required mL/hr to infuse?

• A. 6 mL/hr
• B. 8 mL/hr
• C. 10 mL/hr
• D. 12 mL/hr

Answer: (B)

Calculating IV infusion rate from a weight-based dose and solution strength is done by turning the prescribed units per hour into a volume per hour using the concentration of the IV solution.

First find the required units per hour: 12 units/kg/hr × 70 kg = 840 units/hr. The solution provides 25,000 units in 250 mL, which is 100 units per mL. To get 840 units per hour, you need 840 ÷ 100 = 8.4 mL/hr. Since infusion rates are given as whole mL per hour in the answer options, you round to the nearest whole number, which makes 8 mL/hr the appropriate choice.

Therefore, the required infusion rate is 8 mL/hr.