Question - Calculations

a) A 55 year old (62kg) is prescribed one dose of 40 mEq KCl to be administered to correct his hypokalemia. Your pharmacy stocks 10 ml vials of KCl 2mEq/mL. The manufacturer recommends the maximum concentration for administration is 10mEq/100ml and the max rate of administration is 0.5 mEq/kg/hr

i) How much diluent would you need to prepare the patient’s dose? (1 mark)

ii) From the solution you prepared for this patient, what specific rate of administration would you inform the nurse to give the medication? (2 mark)

iii) How long would you anticipate the infusion time to be? (1 mark)

b) You would like to prepare 30 mL of eye drops containing 1% (w/v) of pilocarpine and 2% (w/v) procaine. How many mL of 0.9% (w/v) sodium chloride should be used to make the above eye drops isotonic?

(freezing point of depression of 1% solution of pilocarpine = 0.14, procaine = 0.11, sodium chloride = 0.576) (4 marks)

c) How many mL of a 18% (w/v) concentrate of benzalkonium chloride should be used in preparing 300mL of a stock soln such that 15 ml diluted to a litre will yield a 1:5000 solution? (4 marks)

d) An orally administered drug used to treat asthma is 55% bioavailable. The patient is currently taking 5 mg daily and wishes to switch to the inhalation form of the drug, which is 87% bioavailable. How many sprays of the drug in inhalational form should the patient use every 12 hours if each meteres spray delivers 500mcg of drug? (4 marks)

e) A hospital pharmacist is required to use three lots of ichthammol ointment containing 50%, 20% and 5% ichthammol respectively. In what proportion should they be mixed to prepare 500g of 10% ichthammol ointment? (4 marks)

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