A 65-year-old male with chronic atrial fibrillation is prescribed warfarin. Warfarin works by:

Correct Answer: B

Rationale: Correct Answer: B - Inhibiting the production of clotting factors by the liver Rationale: 1. Warfarin is a vitamin K antagonist that inhibits the production of vitamin K-dependent clotting factors (Factors II, VII, IX, X) by the liver. 2. By reducing the production of these clotting factors, warfarin helps prevent blood clots in patients with conditions like atrial fibrillation. 3. Thrombin is a key enzyme in the blood clotting process, but warfarin does not directly inhibit its action. 4. Blocking platelet aggregation is the mechanism of action for antiplatelet drugs like aspirin, not warfarin. 5. Inhibiting fibrinogen activation is not a mechanism of action for warfarin, as it primarily targets the production of clotting factors.

Correct Answer: B

Rationale: The correct answer is B: Metformin. Metformin is the first-line treatment for type 2 diabetes mellitus due to its effectiveness, safety profile, and low cost. It works by decreasing glucose production in the liver and improving insulin sensitivity. Insulin (choice A) is usually reserved for when other treatments fail. Sulfonylureas (choice C) can cause weight gain and hypoglycemia. DPP-4 inhibitors (choice D) are typically used as second-line agents.

Correct Answer: A

Rationale: The correct answer is A: Blocking aldosterone receptors. Spironolactone is a potassium-sparing diuretic that works by blocking aldosterone receptors in the distal convoluted tubules of the kidneys. By inhibiting aldosterone, spironolactone reduces sodium and water retention, decreases potassium excretion, and helps reduce fluid overload in heart failure patients. Choices B, C, and D are incorrect because spironolactone does not directly increase sodium and water excretion in the kidneys, inhibit the action of angiotensin II, or block beta-1 adrenergic receptors in the heart.

Correct Answer: B

Rationale: The correct answer is B: Phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are used for treating erectile dysfunction by increasing blood flow to the penis. Beta-blockers (A), ACE inhibitors (C), and diuretics (D) are not indicated for erectile dysfunction treatment as they do not target the underlying physiological mechanisms responsible for erectile function. PDE5 inhibitors specifically target the vasodilation process in the penis, leading to improved erectile function.

Correct Answer: A

Rationale: The correct answer is A: Osteoporosis. Proton pump inhibitors (PPIs) can inhibit calcium absorption, potentially leading to osteoporosis. PPIs reduce stomach acid production, increasing the risk of bone fractures. B: Gastritis is incorrect as PPIs are actually used to treat gastritis by reducing stomach acid. C: Weight loss is incorrect as PPIs are not associated with weight loss. D: Hypoglycemia is incorrect as PPIs do not affect blood sugar levels significantly.