Cephalosporines are drugs of choice for treatment of:

Correct Answer: C

Rationale: Cephalosporins are broad-spectrum antibiotics effective against both gram-positive and gram-negative bacteria. They are commonly used when penicillins are ineffective. This makes choice C the correct answer, as it accurately reflects the versatility and effectiveness of cephalosporins. A: Gram-positive microorganisms - Incorrect. Cephalosporins are effective against both gram-positive and gram-negative bacteria. B: Gram-negative microorganisms - Incorrect. Cephalosporins are effective against both gram-positive and gram-negative bacteria. D: Only bacteroide infections - Incorrect. Cephalosporins are effective against a wide range of bacteria, not limited to just bacteroide infections.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Saquinavir is a protease inhibitor used in the treatment of HIV by blocking viral proteases essential for viral replication. 2. Rimantadine is an antiviral drug used for influenza A virus, not inhibiting viral proteases. 3. Acyclovir is an antiviral drug for herpes simplex virus, working by inhibiting viral DNA synthesis, not proteases. 4. Zalcitabine is a nucleoside analog used for HIV, but it inhibits reverse transcriptase, not viral proteases. Summary: Saquinavir is the correct answer as it specifically inhibits viral proteases crucial for viral replication. The other choices target different viral enzymes or processes, making them incorrect for this question.

Correct Answer: C

Rationale: The correct answer is C: Nitroglycerin. Nitroglycerin is a vasodilator that works by releasing nitric oxide, which leads to decreased platelet aggregation. This helps improve blood flow and reduce symptoms like chest pain in patients with heart conditions. Propranolol (A) is a beta-blocker that doesn't directly affect platelet aggregation. Isosorbide mononitrate (B) is a vasodilator but doesn't have a significant impact on platelet aggregation. Nifedipine (D) is a calcium channel blocker that also doesn't directly influence platelet aggregation.

Correct Answer: A

Rationale: The correct answer is A: Severe postural hypotension. Adding a third drug that decreases central sympathetic outflow (possibly a centrally acting alpha-2 adrenergic agonist) can lead to a sudden drop in blood pressure upon standing, causing postural hypotension. This occurs due to decreased sympathetic tone leading to vasodilation and reduced vascular tone. This effect is more likely to occur shortly after initiating therapy with the new drug. Choice B: Megaloblastic anemia is not a common adverse effect of drugs that decrease sympathetic outflow. Choice C: Palpitations are not typically associated with drugs that decrease sympathetic outflow. Choice D: Pronounced sedation is not a common side effect of centrally acting sympatholytic drugs.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.