Route of administration of plicamycin is:

Correct Answer: A

Rationale: The correct answer is A: Intravenous. Plicamycin is a cytotoxic antibiotic that is administered intravenously to ensure direct delivery into the bloodstream for optimal absorption and distribution to target tissues. Subcutaneous and intranasal routes are not suitable for plicamycin due to its potency and potential irritation at the injection site. Oral administration is ineffective as plicamycin is poorly absorbed through the gastrointestinal tract and extensive first-pass metabolism would render it ineffective. Therefore, intravenous administration is the most appropriate route for plicamycin to achieve desired therapeutic effects.

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: Rationale for Correct Answer (C - Metronidazole or emetine): 1. Metronidazole is the drug of choice for hepatic amebiasis due to its high efficacy against Entamoeba histolytica in the liver. 2. Emetine is an alternative option for hepatic amebiasis treatment, especially in cases of resistance to metronidazole. 3. Both drugs have good tissue penetration and are effective against the protozoa causing hepatic amebiasis. Summary of Incorrect Choices: A: Diloxanide or iodoquinol - These drugs are primarily used for treating non-invasive intestinal amebiasis, not the hepatic form. B: Tetracycline or doxycycline - These antibiotics are not the first-line treatment for hepatic amebiasis. D: Erythromycin or azithromycin - These antibiotics are not effective against Entamoeba histolytica in the liver

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.