Question

1. a prescription for oral clarithromycin suspension 15 mg/kg/day divided bid × 7 days is faxed to the pharmacy for a female pediatric patient weighing 44 pounds. the maximum single dose is 500 mg. which bottle size should be selected to fill this prescription? clarithromycin 125 mg/5 ml (50 ml) clarithromycin 125 mg/5 ml (75 ml) clarithromycin 125 mg/5 ml (100 ml) clarithromycin 125 mg/5 ml (150 ml)

Explanation:

Step1: Convert weight to kg

Weight = $44\ \text{lb} \times \frac{1\ \text{kg}}{2.2\ \text{lb}} = 20\ \text{kg}$

Step2: Calculate daily dose

Daily dose = $15\ \text{mg/kg/day} \times 20\ \text{kg} = 300\ \text{mg/day}$

Step3: Calculate single dose (BID)

Single dose = $\frac{300\ \text{mg/day}}{2} = 150\ \text{mg/dose}$ (≤500mg max)

Step4: Calculate mL per dose

Concentration = $\frac{125\ \text{mg}}{5\ \text{mL}} = 25\ \text{mg/mL}$
mL per dose = $\frac{150\ \text{mg}}{25\ \text{mg/mL}} = 6\ \text{mL/dose}$

Step5: Total mL needed

Total doses = $2\ \text{doses/day} \times 7\ \text{days} = 14\ \text{doses}$
Total mL = $6\ \text{mL/dose} \times 14\ \text{doses} = 84\ \text{mL}$

Step6: Select smallest bottle ≥84mL

50mL <84mL; 75mL <84mL; 100mL ≥84mL; 150mL too large

Answer:

Clarithromycin 125 mg/5 mL (100 mL)