Which of the following medications is used to treat tuberculosis by inhibiting bacterial RNA synthesis?

Correct Answer: B

Rationale: The correct answer is B: Rifampin. Rifampin is used to treat tuberculosis by inhibiting bacterial RNA synthesis through binding to the beta subunit of bacterial RNA polymerase. This inhibits transcription and ultimately leads to bacterial cell death. Isoniazid (choice A) targets mycolic acid synthesis, not RNA synthesis. Amoxicillin (choice C) and Azithromycin (choice D) are antibiotics that work by interfering with bacterial cell wall synthesis or protein synthesis, respectively, not RNA synthesis. Thus, Rifampin is the correct choice for treating tuberculosis by inhibiting bacterial RNA synthesis.

Correct Answer: A

Rationale: The correct answer is A because carvedilol is a non-selective beta-blocker that blocks both beta-1 and beta-2 adrenergic receptors. By blocking these receptors, carvedilol decreases heart rate, cardiac output, and blood pressure, which helps in managing heart failure. Choices B, C, and D are incorrect because carvedilol does not increase heart rate or contractility (choice B), relax vascular smooth muscle (choice C), or inhibit aldosterone secretion (choice D). Carvedilol's mechanism of action primarily involves blocking beta-adrenergic receptors to improve heart function in heart failure patients.

Correct Answer: A

Rationale: Rationale: Clarithromycin is the correct choice because it is commonly used in combination therapy to treat Helicobacter pylori infections. It is often prescribed along with other antibiotics like amoxicillin and a proton pump inhibitor like omeprazole for effective eradication of the bacterium. Metronidazole is also used in H. pylori treatment regimens, but clarithromycin is more commonly preferred. Azithromycin is not typically used for H. pylori eradication. Omeprazole is a proton pump inhibitor that helps reduce stomach acid but is not directly used to treat the infection itself.

Correct Answer: B

Rationale: The correct answer is B: Inhibiting osteoclast-mediated bone resorption. Denosumab is a monoclonal antibody that works by inhibiting osteoclast activity, thereby reducing bone resorption. Osteoclasts are responsible for breaking down bone tissue, so inhibiting their function helps to prevent bone loss in conditions like osteoporosis. Choices A and C are incorrect as denosumab does not directly increase bone formation or promote osteoblast activity. Choice D is also incorrect as denosumab does not affect calcium absorption in the intestines.

Correct Answer: A

Rationale: The correct answer is A: Relaxing vascular smooth muscle, leading to vasodilation. Hydralazine is a direct-acting vasodilator that relaxes arterial smooth muscle, resulting in vasodilation, which decreases systemic vascular resistance and blood pressure. This mechanism of action makes it beneficial in conditions like hypertension and heart failure. Choice B is incorrect as hydralazine does not block beta-1 adrenergic receptors in the heart. Choice C is incorrect because hydralazine does not inhibit the action of aldosterone. Choice D is incorrect as hydralazine does not directly affect the excretion of sodium and water in the kidneys.