1. What is the mechanism of action of warfarin and how does it differ from heparin? Explain the implications for monitoring and reversal of anticoagulation. Answer: Warfarin is a vitamin K antagonist that inhibits the synthesis of clotting factors II, VII, IX and X in the liver. Heparin is an antithrombin III activator that inhibits the activity of thrombin and factor Xa in the blood. Warfarin has a delayed onset and offset of action, whereas heparin has an immediate effect. Warfarin requires regular monitoring of the international normalized ratio (INR) to adjust the dose and prevent bleeding or thrombosis. Heparin requires monitoring of the activated partial thromboplastin time (aPTT) or anti-Xa levels. Warfarin can be reversed with vitamin K or prothrombin complex concentrate (PCC). Heparin can be reversed with protamine sulfate. Rationale: This question tests the students' knowledge of the pharmacodynamics, pharmacokinetics and clinical management of two common anticoagulants. 2. What are the main adverse effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs)? How can they be prevented or managed? Answer: The main adverse effects of ACE inhibitors and ARBs are hypotension, hyperkalemia, renal impairment and cough (more common with ACE inhibitors). They can be prevented or managed by adjusting the dose, monitoring blood pressure, electrolytes and renal function, avoiding potassium supplements or potassium-sparing diuretics, and switching to an ARB if cough is intolerable. Rationale: This question tests the students' knowledge of the pharmacotherapy and safety of two common antihypertensive classes. 3. What are the indications, contraindications and interactions of metformin? What are the main precautions and side effects of this drug? Answer: Metformin is a biguanide that lowers blood glucose by reducing hepatic gluconeogenesis, increasing peripheral glucose uptake and decreasing intestinal glucose absorption. It is indicated for type 2 diabetes mellitus, polycystic ovary syndrome (PCOS) and prediabetes. It is contraindicated in patients with renal impairment, liver disease, heart failure, lactic acidosis or hypersensitivity. It interacts with alcohol, iodinated contrast media, cimetidine and other antidiabetic drugs. The main precautions are to monitor renal function, avoid dehydration and discontinue before surgery or contrast procedures. The main side effects are gastrointestinal disturbances, weight loss, lactic acidosis and vitamin B12 deficiency. Rationale: This question tests the students' knowledge of the pharmacology and clinical use of a widely prescribed antidiabetic drug. 4. What are the differences between selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) in terms of their mechanism of action, efficacy, tolerability and drug interactions? Answer: SSRIs and SNRIs are antidepressants that inhibit the reuptake of serotonin in the synaptic cleft, thereby increasing its availability. SNRIs also inhibit the reuptake of norepinephrine, which may enhance their antidepressant effect in some patients.