A physician writes the following prescription order for an 8month old infant (weight 10.5 lbs)

Propranolol suspension 3.4mg/kg/day given twice a day x 1 month

Your institution’s formula is as follows:

i) The pharmacy prepares 500 ml of the above solution to keep in stock. How much (in ml) of the above suspension would the patient need for each dose? (3 marks)

Weight conversion 1 lbs = 0.45 kg

Weight of infant in kg: 10.5 lbs * 0.45 = 4.725 kg

Propranolol dosage 3.4 mg/kg -> 3.4 * 4.725 = 16.065 mg per day

Twice a day dosing - > 16.065/2 = 8.0325 mg per dose

Concentration of the propranolol syrup:

10 mg * 50 = 500mg - > 500mg/100ml or 5mg/ml

Amount of 5mg/ml syrup required for one dose:

8.0325/5 = 1.6 ml

ii) You are asked to freshly prepare a 28-day supply of the above prescription for the patient. How much of each ingredient would you need to ensure sufficient amount but minimal excess? (2 marks)

Amount of syrup required per day: 1.6*2 = 3.2 ml

Amount required for 28 days: 3.2*28 = 89.6ml

Round up to 90 ml of 5mg/ml.

Amount of propranolol needed: 90*5 = 450mg.

Amount of syrup required = 90 ml