a) How many ml of a 17% w/v concentrate of benzalkonium chloride should be used in preparing 300 ml of a stock solution such that 20 ml diluted to 1L will yield a 1:5000 solution? (4 marks)

b) The dose of drug X for a pediatric patient is 20mg/kg Q6H given intravenously over 30 minutes. A 250 mg vial is diluted to 100mL using 0.9% NaCl and administered to a 24 lb child. What should be the flow rate in drops/min if the infusion set delivers 60 drops/ml? (4 marks)

c) Drug X degrades by a zero order process with a rate constant of 0.05 mg/ml/year at room temperature. A 1% (w/v) solution is prepared and stored at room temperature.

i) What concentration will remain after 18 months? (3 marks)

ii) What is the half life of the drug? (3 marks)

d) Rx Oxymetazoline hydrochloride 0.5%

           Boric acid                              qs

           Purified water to                  15 ml

If a pharmacist would like to make an isotonic nose drop (15ml) how many mL of a 5% boric acid solution should be used in compounding the prescription?

(A 1% sodium chloride solution depresses the freezing point of water by 0.576C. A 1% boric acid solution depresses the freezing point of water by 0.288C. A 1% oxymetazoline hydrochloride solution depresses the freezing point of water by 0.176C).

 (4 marks)

e) In what proportion the following four ointments be mixed together to make 10% zinc oxide ointment? (2 marks)

i) 20% zinc oxide ointment

ii) 15% zinc oxide ointment

iii) 5% zinc oxide ointment

iv) 3% zinc oxide ointment