Question

A 450 lb. weanling requires treatment with potassium penicillin at a dose of 22,000 IU/kg q.i.d. The bottle of potassium penicillin has been reconstituted to a dosage strength of 500,000 IU/mL. What’s the correct dosage?

Answer 1

Explanation:

Since the unit conversion from pounds (lbs) to kilograms (kg) follows the relation

                                               $1 \ \text{lb} \ \approx \ 0.45359 \ \text{kg}$,

Using dimensional analysis, the correct dosage in units of mililitres is

           $\text{Dosage} \ = \ 450 \ \text{lb} \ \times \ \displaystyle\frac{0.45359 \ \text{kg}}{1 \ \text{lb}} \ \times \ \displaystyle\frac{22,000 \ \text{IU}}{1 \ \text{kg}} \ \times \ \displaystyle\frac{1 \ \text{mL}}{500,000 \ \text{IU}} \\ \\ \text{Dosage} \ = \ 8.9 \ \text{mL} \ \ \ \ \ \ (1 \ \text{d.p.})$.