MPharm Master of Pharmacy Master of Pharmacy: Pharmacology and Therapeutics 3 — Questions and Answers
Question 1: A 60-year-old diabetic patient develops hypoglycemia while on a sulfonylurea. Which mechanism directly causes insulin secretion with this drug class?
- Activation of GLP-1 receptors on beta cells
- Closure of ATP-sensitive potassium channels in beta cells (Correct answer)
- Inhibition of alpha-glucosidase in the intestinal brush border
- Activation of PPAR-gamma receptors in adipose tissue
Correct answer: Closure of ATP-sensitive potassium channels in beta cells
Sulfonylureas bind the SUR1 subunit of K-ATP channels, closing them and causing membrane depolarization that triggers insulin release regardless of glucose levels.
Question 2: Which pharmacokinetic parameter best predicts antibiotic efficacy for beta-lactams?
- Peak concentration to MIC ratio (Cmax/MIC)
- Area under the curve to MIC ratio (AUC/MIC)
- Time above MIC (T>MIC) (Correct answer)
- Trough concentration
Correct answer: Time above MIC (T>MIC)
Beta-lactam antibiotics exhibit time-dependent killing; their efficacy correlates with the duration free drug concentrations remain above the MIC.
Question 3: A patient on methotrexate develops severe mucositis. Which rescue agent is administered?
- Vitamin B12
- Leucovorin (folinic acid) (Correct answer)
- N-acetylcysteine
- Folic acid
Correct answer: Leucovorin (folinic acid)
Leucovorin bypasses DHFR inhibition by methotrexate by providing a reduced folate form, rescuing normal cells without diminishing antitumor effects.
Question 4: Which adverse effect is most associated with long-term use of proton pump inhibitors?
- Hyperkalemia
- Hypomagnesemia and increased fracture risk (Correct answer)
- Hyperuricemia and gout
- Pulmonary fibrosis
Correct answer: Hypomagnesemia and increased fracture risk
Chronic PPI use impairs active magnesium absorption in the intestine and reduces gastric acid necessary for calcium salt dissolution, increasing fracture risk.
Question 5: A patient taking clozapine develops an absolute neutrophil count of 500/mm³. What is the immediate action?
- Reduce clozapine dose by 50%
- Discontinue clozapine immediately and never rechallenge (Correct answer)
- Add lithium to stimulate granulopoiesis and continue clozapine
- Switch to olanzapine at equivalent dose
Correct answer: Discontinue clozapine immediately and never rechallenge
Agranulocytosis (ANC <500) from clozapine is a life-threatening emergency requiring immediate discontinuation; rechallenge is contraindicated per REMS guidelines.
Question 6: Which mechanism explains the antiarrhythmic action of adenosine in paroxysmal supraventricular tachycardia?
- Blocks sodium channels to slow phase 0 depolarization
- Activates A1 receptors, hyperpolarizing AV nodal cells and slowing conduction (Correct answer)
- Blocks calcium channels in ventricular myocardium
- Prolongs QT interval by blocking potassium channels
Correct answer: Activates A1 receptors, hyperpolarizing AV nodal cells and slowing conduction
Adenosine activates A1 purinergic receptors, opening K+ channels that hyperpolarize AV nodal cells, transiently blocking AV conduction to terminate reentrant SVT.
Question 7: A pharmacist calculates the volume of distribution (Vd) for a drug is 500 L in a 70 kg patient. What does this indicate?
- The drug is extensively bound to plasma proteins and stays in the vascular compartment
- The drug is highly distributed into tissues and not confined to plasma (Correct answer)
- The drug has poor bioavailability and limited absorption
- The drug is primarily eliminated by the kidneys
Correct answer: The drug is highly distributed into tissues and not confined to plasma
A large Vd (>0.6 L/kg) indicates extensive tissue distribution, meaning the drug partitions preferentially into tissues rather than remaining in plasma.
MPharm Master of Pharmacy Master of Pharmacy: Pharmacology and Therapeutics 3
A 60-year-old diabetic patient develops hypoglycemia while on a sulfonylurea.
Which mechanism directly causes insulin secretion with this drug class?