## Part a - Ratios

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 institutionâ€™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**