Rational anti-microbial combination is used to:

Correct Answer: D

Rationale: Rationale: 1. Choice A is correct because combining antimicrobial agents can enhance their effectiveness against resistant strains. 2. Choice B is correct because a combination can target a wider range of microorganisms. 3. Choice C is correct because using a combination can help reduce the chance of resistance developing. Summary: All of the above choices are correct because rational antimicrobial combinations provide synergism, broad coverage, and prevent resistance emergence.

Correct Answer: B

Rationale: Step 1: Tetracyclins are known to have antimalarial properties by inhibiting protein synthesis in Plasmodium species. Step 2: Aminoglycosides (choice A) primarily target bacteria, not parasites like malaria. Step 3: Carbapenems (choice C) and Penicillins (choice D) are both beta-lactam antibiotics that have no significant antimalarial effects. Summary: Tetracyclins are the correct choice as they directly target malaria parasites, while the other options do not possess antimalarial properties.

Correct Answer: B

Rationale: Methotrexate is a folic acid antagonist. It inhibits dihydrofolate reductase, leading to decreased DNA synthesis. This action makes it effective in treating cancer and autoimmune diseases. Purine antagonists target purine synthesis, antibiotics act on bacterial growth, and alkylating agents damage DNA to prevent cell division. Methotrexate's mechanism aligns with folic acid antagonism, making option B the correct choice.

Correct Answer: D

Rationale: The correct answer is D: Nitroprusside. Nitroprusside is a potent vasodilator that can rapidly induce controlled hypotension by relaxing smooth muscle in blood vessels. This helps in minimizing blood loss during surgery. Labetalol (A) is a non-selective beta-blocker with alpha-blocking activity, which may not provide rapid hypotension. Hydralazine (B) is a direct vasodilator that can cause reflex tachycardia and may not be as effective in controlled hypotension. Nifedipine (C) is a calcium channel blocker primarily used for hypertension but does not provide rapid hypotension like nitroprusside.

Correct Answer: D

Rationale: The correct answer is D: Prazosin. Prazosin is an alpha-1 adrenergic blocker that can cause orthostatic hypotension, leading to dizziness and fainting when standing up rapidly. It works by dilating blood vessels, which can cause a sudden drop in blood pressure upon standing. Propranolol (A) is a beta-blocker and can cause dizziness but is less likely to cause orthostatic hypotension. Minoxidil (B) is a vasodilator that can cause rapid heart rate but not typically dizziness upon standing. Hydralazine (C) is a direct vasodilator that can cause reflex tachycardia but is less likely to cause orthostatic hypotension compared to alpha-1 blockers like Prazosin.