All of the following drugs are antibiotics, EXCEPT:

Correct Answer: C

Rationale: The correct answer is C: Co-trimoxazole. Co-trimoxazole is a combination of sulfamethoxazole and trimethoprim, which are not antibiotics but rather antimicrobial agents. Streptomycin, Penicillin, and Chloramphenicol are all antibiotics that target and kill bacteria. Antibiotics specifically target bacterial infections, while antimicrobial agents can target a broader range of microbes. Therefore, Co-trimoxazole does not fall under the category of antibiotics, making it the correct answer.

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.

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.