DHA Pharmacist Clinical Pharmacology 1 — Questions and Answers
Question 1: A patient taking simvastatin is prescribed clarithromycin for a respiratory infection. What is the primary concern?
- Clarithromycin inhibits CYP3A4, dramatically increasing simvastatin levels and the risk of myopathy/rhabdomyolysis (Correct answer)
- No clinically significant interaction exists
- The combination reduces the efficacy of clarithromycin
- Simvastatin increases clarithromycin levels
Correct answer: Clarithromycin inhibits CYP3A4, dramatically increasing simvastatin levels and the risk of myopathy/rhabdomyolysis
Clarithromycin is a potent CYP3A4 inhibitor; co-administration with simvastatin (a CYP3A4 substrate) raises statin plasma levels, greatly increasing the risk of myopathy and rhabdomyolysis.
Question 2: Which receptor type mediates the bronchodilator effect of salbutamol (albuterol)?
- Beta-2 adrenergic receptors in bronchial smooth muscle (Correct answer)
- Alpha-1 adrenergic receptors
- Muscarinic M3 receptors
- H1 histamine receptors
Correct answer: Beta-2 adrenergic receptors in bronchial smooth muscle
Salbutamol is a selective beta-2 adrenergic agonist; its binding to beta-2 receptors in bronchial smooth muscle activates adenylyl cyclase, increasing cAMP and causing bronchodilation.
Question 3: What is the mechanism of action of metformin in type 2 diabetes?
- Activates AMPK to reduce hepatic glucose production and improve insulin sensitivity (Correct answer)
- Stimulates pancreatic beta cells to secrete more insulin
- Blocks alpha-glucosidase to delay carbohydrate absorption
- Inhibits SGLT-2 to increase urinary glucose excretion
Correct answer: Activates AMPK to reduce hepatic glucose production and improve insulin sensitivity
Metformin primarily activates AMP-activated protein kinase (AMPK), which suppresses hepatic gluconeogenesis and improves peripheral insulin sensitivity without causing hypoglycaemia.
Question 4: Which adverse effect is uniquely associated with ACE inhibitors and distinguishes them from ARBs?
- Dry, persistent cough caused by bradykinin accumulation (Correct answer)
- Hyperkalaemia
- Angioedema (also seen with ARBs but much less commonly)
- Hypotension on first dose
Correct answer: Dry, persistent cough caused by bradykinin accumulation
ACE inhibitors prevent the breakdown of bradykinin in the lungs; accumulation of bradykinin causes the characteristic dry, persistent cough not seen with ARBs.
Question 5: What is the pharmacological basis for using atropine to treat bradycardia?
- Atropine blocks muscarinic receptors, preventing acetylcholine-induced slowing of the heart rate (Correct answer)
- Atropine stimulates beta-1 receptors directly
- Atropine releases norepinephrine from nerve terminals
- Atropine blocks potassium channels in the SA node
Correct answer: Atropine blocks muscarinic receptors, preventing acetylcholine-induced slowing of the heart rate
Atropine is a competitive muscarinic antagonist that blocks vagal (acetylcholine-mediated) slowing of the SA node, thereby increasing heart rate.
Question 6: Which enzyme does aspirin irreversibly inhibit to achieve its antiplatelet effect?
- Cyclooxygenase (COX-1) (Correct answer)
- Phospholipase A2
- Thrombin
- Factor Xa
Correct answer: Cyclooxygenase (COX-1)
Aspirin irreversibly acetylates and inhibits COX-1 in platelets, preventing thromboxane A2 synthesis and thereby inhibiting platelet aggregation for the platelet's entire lifespan.
DHA Pharmacist Clinical Pharmacology 1
A patient taking simvastatin is prescribed clarithromycin for a respiratory infection.
What is the primary concern?