PART II-ESSAY QUESTIONS 

1. Pharmaceutical Calculations 

a) A child weighing 33 pounds requires a dose of 8 mg/kg of drug X. Given that a 5 mL dose is to be given each time, what volume of water must be added when the drug X powder is reconstituted? Instruction on the label indicates that dilution to 120 mL (by adding 100 mL of water) gives 125 mg drug X per 5 mL. 

(4 marks) 

b) A prescription requires the preparation of 2-g suppositories. Each one contains 30 mg morphine sulphate and 150 mg aspirin in theobroma oil base. Calculate the amount of each ingredient for 20 suppositories. The displacement values are: 1.6 for morphine sulphate and 1.1 for aspirin. Mould calibration is 1.05. 

(4 marks) 

c) You have 20%, 15%, 2% zinc oxide ointment. The prescription calls for 80 g of  10% zinc oxide ointment. Your pharmacy has 16 g of 15% zinc ointment expiring soon and therefore these must be used first. What is the amount required for each zinc oxide ointment? 

(2 marks)

d) Patient EJM is a 35-year-old female and weighs 143 lb. She is admitted for chronic immune thrombocytopenic purpura ("ITP") and requires infusion of intravenous immunoglobulin ("IVIG").  (3 marks) 

(i) The regimen is IVIG 1 g/kg intravenous infusion for 2 consecutive days. Calculate the dose for each infusion for EJM.

(ii) The IVIG product is a 10% liquid formulation, available in 50 mL, 100 mL, and 200 mL single-use vials. You are going to procure the medication for her entire IVIG regimen. How many vials do you need to order for this patient? 

(iii) The instruction for the first infusion is as follows- 

"Initiate infusion at a rate of 0.5 mg/kg/min. In the absence of infusion toxicity, increase infusion rate by 0.5 mg/kg/min increments every 30 minutes, to a maximum of 4 mg/kg/min." 

What is the minimum infusion time for her first infusion, assuming she does not have any infusion toxicity? 

e) Subsequently, patient EJM from part (d) presents with urinary tract infection. Her latest serum creatinine is 76 μmol/L. The physician prescribed gentamicin 300mg IV Q24H infused over 1 hour. (3 marks) 

(i) Gentamicin volume of distribution is estimated to be 0.25 L/kg, and clearance is expected to 100% of creatinine clearance. What is the expected half-life of gentamicin in this patient? 

(ii) Your pharmacy stocks gentamicin 80 mg/2mL vials. Your hospital policy states that extended-interval aminoglycosides should be diluted in 100 mL NS. What is the appropriate infusion rate? 

(iii) Therapeutic drug monitoring of extended-interval aminoglycoside typically involves taking a single blood level in the middle of the dosing interval. What is the expected steady state concentration at 10 hours after start of infusion? 

f) After receiving the gentamicin as in part (e), patient EJM develops hypokalemia and the doctor orders potassium chloride ("KCI") 30 mmol to be added to 500 mL of Dextrose 5% + NaCl 0.45% ("D5-2NS"), and to be infused as a continuous infusion over 5 hours. 

(3 marks) 

(i) The KCl is available in 14.9% concentrated solution. What is the volume required to prepare the infusion solution? (molecular weight of KCl is 74.5 g/mol) 

(ii) What is the approximate concentration of potassium (in mEq/L) in the infusion solution? 

(iii) What is the approximate osmolarity (in mOsmol/L) of the infusion solution? 

g) Eventually patient EJM in part (f) is discharged home with an oral antibiotic. Because she cannot swallow big capsules, she requests to have oral solution instead. 

(i) The doctor prescribed cefalexin 250mg PO BD for 5 days. Your pharmacy stocks cefalexin 250 mg oral capsules and 125 mg/5mL oral suspension in 60 mL bottles. What is the total quantity to be dispensed for this prescription? 

(1 mark) 

2. Mr Lee, a 68-year-old male, visits the community pharmacy with a new prescription for apixaban. He has a history of persistent atrial fibrillation ("AF") and recently experienced proximal deep vein thrombosis ("DVT") in his left lower extremity. He has been on warfarin therapy for the past two years, but his international normalised ratio ("INR") has been difficult to maintain within the therapeutic range. His time in therapeutic range ("TTR") is calculated to be approximately 40%. Over the past six months, Mr Lee's INR values have been inconsistent, as demonstrated by the following figures: 

• Visit 1: INR 1.7
• Visit 2: INR 3.4 
• Visit 3: INR 1.9 
• Visit 4: INR 3.2 
• Visit 5: INR 2.5
• Visit 6: INR 4.1 

Other medical conditions include hypertension, type 2 diabetes, and a prior history of peptic ulcer disease. Current medications include metformin, lisinopril, and atorvastatin. 

a) Explain the factors that should be considered when selecting an appropriate anticoagulant for Mr Lee and how each of these factors may impact the choice of therapy. (4 marks) 

b) Discuss the appropriateness of apixaban as an anticoagulant for Mr Lee considering his medical history and current medications and provide rationale. Please provide the appropriate dosing regimen for apixaban in the primary treatment phase of DVT. (5 marks) 

c) Is it possible to discontinue Mr Lee's anticoagulation therapy after the primary  treatment phase of 3-6 months for DVT? Why or why not? (2 marks)

d) What are the key patient counselling points and monitoring parameters that should be considered when transitioning Mr Lee from warfarin to apixaban therapy? (4 marks) 

3. VIRGAN® 1.5 mg/g, eye gel contains an antiviral agent called ganciclovir (molecular weight=255.23 g/mol, slightly soluble in water, logP=-1.65). It is indicated in the treatment of certain superficial and viral eye infections (cornea). The eye gel also contains carbomer (carbopol 974P), sorbitol, sodium hydroxide, benzalkonium chloride and purified water. 

a) Describe the function of carbomer (carbopol 974P), sorbitol, sodium hydroxide, and benzalkonium chloride in the formulation. (4 marks)

b) From the properties of ganciclovir, please suggest why it can be developed into an eye gel. (2 marks) 

c) Ganciclovir is also available in oral and intravenous dosage forms. Please discuss the advantages and disadvantages of the eye gels over the other two administration routes. (3 marks) 

d) Apart from eye gels, eye drops and ointments are also common topical ophthalmic drug delivery systems. Please discuss the differences between these dosage forms. (6 marks) 

4. Ms S is an 85-year-old female living in a residential care home. Her medical history includes schizophrenia, constipation and sialorrhea. She has no signs or symptoms of extrapyramidal side effects now. She had been previously admitted to hospital due to generalised tonic-clonic seizure, severe faecal impaction and gastrointestinal hypomotility. Medications before admission were: 

• Clozapine 550 mg nocte 
• Benzhexol 4 mg tds 
• Lactulose 10 ml bd 
• Senna 15 mg nocte 

After medical treatment at hospital for a few days, she was discharged back to residential care home with the following medications: 

• Clozapine 300 mg nocte
• Benzhexol 4 mg tds 
• Lactulose 15 ml bd 
• Senna 15 mg nocte 
• Psyllium 1 teaspoon tds 
• Levetiracetam 750 mg bd 

Her psychotic symptoms had been previously well controlled before admission. But after adjustment of medications and going back to the residential care home, she has frequent relapse of psychosis. 

a) Please identify the likely cause of Ms S's seizure, intestinal obstruction in her previous admission, and the relapse of psychosis after discharge, respectively. (3 marks)

b) The medical team asked for your advice for pharmacological interventions. Perform a full medication review and give your advice on the medication regimen of this patient. Provide rationale for your recommendations. (12 marks) 

5. KJP is a 68-year-old male admitted to a hospital due to severe rectal bleeding. His medical history includes prostatic cancer (diagnosed in December 2023 and received radiation therapy in March 2024), prostatitis, osteoporosis, hypertension and dyslipidaemia. 

Medications prior to admission: 

• Losartan 25 mg daily 
• Amlodipine 10 mg daily 
• Calcium carbonate 1000 mg QID 
• Atorvastatin 40 mg daily 
• Ezetimibe 10 mg daily 
• Cholecalciferol 1000 international units daily 
• Levofloxacin 500 mg daily for 4 weeks (started 20 days ago) 

On day 1 of hospitalisation, the lab values are: 

• Estimated glomerular filtration rate ("eGFR"): 53 ml/min 
• Haemoglobin 9.7 (ref: 13.5-17 g/dL) 
• Haematocrit: 30.6% (ref: 40-52%) 
• Mean Corpuscular Volume ("MCV"): 84.9 (ref: 81-97 fL) 
• Mean Corpuscular Haemoglobin ("MCH"): 27.4 (ref: 27-32 pg/cell) 
• Mean Corpuscular Haemoglobin Concentration ("MCHC"): 32.7 (ref: 31-35 g/dL) 
• Total calcium: 1.9 (ref: 2.1-2.6 mmol/L) 
• Sodium: 141 (ref: 136-148 mmol/L) 
• Potassium: 3.5 (ref: 3.6-5.0 mmol/L) 
• Phosphate: 0.6 (ref: 0.8-1.4 mmol/L)
• Albumin within normal limits 

a) KJP's usual medications are not withheld. After the morning ward round, a doctor prescribed 20% calcium chloride in 50 mL NS IV infusion over 5 minutes. Please comment on the doctor's order for the treatment of hypocalcaemia. You may make suggestions where appropriate. (8 marks) 

b) On the same day, the doctor prescribed PO 2 g sucralfate Q4h for 2 doses to manage his rectal bleed caused by proctitis due to radiation. When verifying the order, a warning "separate administration of sucralfate and calcium by at least 2 hours" is shown. What is the rationale of this warning? What suggestions can be made concerning the calcium preparation in (a) and KJP's usual medicines? (5 marks) 

c) KJP's doctor also prescribed 10 mmol of potassium phosphate (KH2PO4 + K2HPO4) IV infusion over 2.5 hours. The ward nurse would like to know if it can be co-administered with the calcium preparation in (a) via the same IV line, and why. (2 marks) 

END OF PAPER