Combination of sulfonamides with trimethoprim:

Correct Answer: B

Rationale: Step-by-step rationale for Choice B being correct: 1. Trimethoprim inhibits bacterial dihydrofolate reductase. 2. Sulfonamides inhibit dihydropteroate synthetase. 3. Combination blocks sequential steps in folate synthesis. 4. Synergistic effect enhances antimicrobial activity. Summary: A: Incorrect. Combination does not decrease unwanted effects of sulfonamides. C: Incorrect. Combination does not decrease antimicrobial activity. D: Incorrect. Combination does not increase elimination of sulfonamides.

Correct Answer: C

Rationale: The correct answer is C: Mitotic arrest at metaphase. Plant alkaloids like vinca alkaloids and taxanes disrupt microtubule function, leading to mitotic arrest at metaphase. This prevents cell division and ultimately inhibits cancer cell growth. Option A is incorrect because plant alkaloids do not directly inhibit DNA-dependent RNA synthesis. Option B is incorrect as cross-linking of DNA is not a mechanism of action for plant alkaloids. Option D is incorrect as plant alkaloids do not target aromatases. In summary, the correct mechanism for plant alkaloids is disrupting microtubule function, leading to mitotic arrest at metaphase.

Correct Answer: D

Rationale: The correct answer is D: Procainamide. Procainamide is a Class 1A antiarrhythmic agent that is effective for both supraventricular and ventricular arrhythmias. It works by blocking sodium channels, prolonging the action potential duration. This helps to stabilize the cardiac rhythm. Lidocaine (A) is more specific for ventricular arrhythmias. Verapamil (B) is a calcium channel blocker more suitable for supraventricular arrhythmias. Propranolol (C) is a beta-blocker that is effective for preventing arrhythmias but not as effective for acute treatment compared to procainamide.

Correct Answer: A

Rationale: The correct answer is A: Hydrochlorothiazide. This diuretic is appropriate for a patient with hypertension due to its ability to reduce blood volume and lower blood pressure. It is often recommended as a first-line treatment for essential hypertension. Propranolol (B) is a beta-blocker that may not be as effective as a diuretic in this case. Captopril (C) is an ACE inhibitor that may be used as an alternative, but not as the most appropriate choice. Clonidine (D) is a centrally acting alpha-2 agonist and typically considered a second-line treatment option.

Correct Answer: B

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