Pharmaceutical calculations

a) What is the total osmolarity (mOsm/L) A solution containing 80 mEq KCl in 500 ml of 0.9% NaCl? (MW = Cl = 35.5; K = 39; Na= 23) (3 marks)

b) A prescription calls for 250 mL of 2.5% Sodium Bicarbonate solution. You have the 50 g/250 mL sodium Bicarbonate concentrate and D5W as diluent. How much of each would you need to prepare the above prescription? (1 mark)

c) A 78-year-old female (wt = 52. 4 kg) is prescribed Amiodarone IV infusion at 1 mg/ min for six hours. The preparation of amiodarone IV solution available in your hospital is 150 mg/3 mL vials. The manufacturer recommends the solution to be diluted to a concentration of less than 2 mg/mL in D5W Or normal saline (“NS“)

(i) How would you prepare a 6-hour dose for the patient ? (2 marks)

(ii) The next day after admission, the patient is prescribed KCl SR (Slow-K) 600 mg PO daily. How much K+ (in mEq) is in each dose of KCl? (MW = CL equals 35.5; K equals 39). (2 marks)

d) You receive a stat medication order for Intravenous fluids for a 10 month old patient (wt= 16.0 lbs). The medication order is written for 0.9% NS + D5W at 4 mL/kg/hour continuous infusion.

(i) Your hospital stocks 500 mL solutions of the above IV fluids. At what rate should the nurse administer the solution? (2 marks)

(ii) What is the total duration of infusion for a 500 mL IV bag? (1 mark)

e) A 67-year-old male patient (ht = 162 cm; wt= 59.3 kg) is admitted to the ICU for severe methicillin resistant Staphylococcus aureus (“MRSA”) pneumonia. The patient is prescribed Vancomycin 500 mg IV Q6 hours. The treating physician would like to make sure the prescribed dose reaches the target area under the curve (“AUC”) of 400 - 600.

(i) The patient’s current serum creatinine is 95 µmol/L. What is the patient's estimated creatinine clearance (“CrCl”)? (2 marks)

(ii) The estimated clearance for Vancomycin based on population parameters is (0.689* CrCl +3.66) mL/min. What is the patient’s estimated vancomycin clearance (L/hr)? (1 mark)

(iii)  What is the expected AUC of Vancomycin in this patient? (2 marks)

(iv) What is the expected half life of Vancomycin for this patient? Estimated Vd (L) equals 89*bodyweight. (2 marks)

(v) A few days later, the physician writes a medication order for Acyclovir IV 250 mg/m² / dose  every 12 hours. What is the total amount of acyclovir (mg) the patient will receive per dose?