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: In this question, the correct answer is D) Verapamil. Verapamil is a calcium channel blocker that decreases heart rate by inhibiting calcium ion influx, leading to decreased myocardial oxygen demand. This effect helps in the treatment of angina by reducing the workload of the heart and preventing vasospastic angina attacks. Option A) Isosorbide dinitrate and option C) Nitroglycerin are nitrates that primarily work by dilating blood vessels to increase oxygen supply to the heart muscle. While they are effective in treating angina, they do not consistently decrease heart rate like verapamil. Option B) Nifedipine is a calcium channel blocker like verapamil, but it mainly acts on the peripheral vasculature to reduce blood pressure and coronary vasospasm. It does not have as significant an effect on heart rate as verapamil. Educationally, understanding the mechanisms of action of different cardiovascular drugs is crucial for prescribing the most appropriate treatment for patients with angina. Verapamil's specific effect on heart rate makes it a suitable choice for patients with angina who also require heart rate control. This knowledge helps healthcare providers tailor treatment plans to individual patient needs effectively.