Correct Answer: A

Rationale: The correct answer is A: Use of nitrates. Sildenafil (Viagra) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both cause vasodilation, which can lead to a dangerous drop in blood pressure. Choice B (Use of antihypertensive medications) is incorrect because antihypertensive medications are not a critical contraindication for sildenafil use. Choice C (History of hypertension) is incorrect as it is not a contraindication for sildenafil; in fact, sildenafil is sometimes used in patients with hypertension. Choice D (History of peptic ulcer disease) is also incorrect as it is not a critical contraindication for sildenafil use.

Correct Answer: B

Rationale: The correct answer is B: 'vigilant adherence to the drug regimen.' When initiating oral contraceptive therapy, the success of preventing pregnancy relies heavily on the patient's commitment to following the prescribed regimen consistently. Compliance with taking the oral contraceptives as directed is crucial for their effectiveness. Choice A, 'current health status,' is not the primary factor for successful prevention of pregnancy with oral contraceptives. Choice C, 'knowledge of sexual health,' while important, is not the primary determinant of contraceptive efficacy. Choice D, 'risk factors for adverse effects,' though relevant for monitoring and managing side effects, is not the primary focus for ensuring contraceptive success.

Correct Answer: B

Rationale: Swelling during acute inflammation is primarily caused by the accumulation of fluid exudate in the affected tissues. This fluid exudate contains proteins and cells that leak from blood vessels due to increased vascular permeability. Collagenase (Choice A) is an enzyme that breaks down collagen and is not directly responsible for swelling. Lymphocytic margination (Choice C) is the process where white blood cells line up along the blood vessel walls, which does not directly cause swelling. Anaerobic glycolysis (Choice D) is a metabolic process that occurs in the absence of oxygen and is not related to the mechanism of swelling in acute inflammation.

Correct Answer: B

Rationale: The correct answer is B: Metronidazole (Flagyl). When treating extraintestinal amebiasis, chloroquine is often used in combination with metronidazole to ensure the eradication of the parasite. Metronidazole helps to target the infection more effectively. Choices A, C, and D are incorrect. Iodoquinol (Yodoxin) is another antiprotozoal agent but is not typically used in combination with chloroquine for amebiasis. Metyrosine (Demser) is used in the management of pheochromocytoma, and carbamazepine (Tegretol) is an anticonvulsant and mood-stabilizing drug, neither of which are indicated for extraintestinal amebiasis.

Correct Answer: C

Rationale: The correct answer is C. Hormonal contraceptives increase blood levels of clotting factors, particularly factors II, VII, IX, and X. This elevation in clotting factors can predispose individuals to thromboembolic events, including blood clots. Choices A, B, and D are incorrect because hormonal contraceptives do not have a significant effect on serum triglycerides and cholesterol, platelet levels, or causing direct injury to blood vessel linings as the primary mechanism for clot formation.