The following drug can be used in prophylaxis of migraine:

Correct Answer: C

Rationale: Propranolol is the correct answer for migraine prophylaxis due to its beta-blocking properties, reducing sympathetic nervous system activity. This helps prevent migraine attacks. Noradrenaline and amphetamine increase sympathetic activity, exacerbating migraines. Ergotamine is used for acute migraine attacks, not prophylaxis.

Correct Answer: D

Rationale: The correct answer is D: Haloperidol. Haloperidol is a dopamine receptor antagonist, which means it blocks dopamine receptors. Dopamine induces renal vasodilation by acting on dopamine receptors in the kidneys. Therefore, blocking these receptors with haloperidol would antagonize the renal vasodilation effect of dopamine. A: Propranolol is a beta-blocker that acts on beta receptors, not dopamine receptors. B: Atropine is a muscarinic antagonist and does not affect dopamine receptors. C: Prazosin is an alpha-1 adrenergic antagonist and does not target dopamine receptors.

Correct Answer: A

Rationale: Neostigmine is the correct choice for treating myasthenia gravis as it is an acetylcholinesterase inhibitor that increases acetylcholine levels, improving muscle strength. Pilocarpine is a muscarinic agonist used for glaucoma. Succinylcholine is a depolarizing neuromuscular blocker used for intubation. Tubocurarine is a non-depolarizing neuromuscular blocker.

Correct Answer: D

Rationale: Adrenaline is a sympathomimetic drug that acts on adrenergic receptors. In acute situations like allergic reactions, bronchial asthma, and heart block, adrenaline can be beneficial due to its bronchodilator and vasoconstrictor effects. However, in angina pectoris, which is caused by reduced blood flow to the heart muscle, the vasoconstrictor effect of adrenaline can worsen the condition by increasing the workload of the heart. Therefore, adrenaline should not be used in angina pectoris.

Correct Answer: C

Rationale: Rationale: Labetalol is a non-selective beta-blocker that reduces cardiac contractility by blocking beta-1 receptors and inhibits sympathetic-mediated vasoconstriction by blocking alpha-1 receptors. Albuterol (A) is a beta-2 agonist, which increases cardiac contractility. Atropine (B) is a muscarinic antagonist, which increases heart rate and does not affect vasoconstriction. Isoproterenol (D) is a non-selective beta agonist, which increases cardiac contractility and vasodilation. Thus, C (Labetalol) is the only drug that can lower blood pressure by both mechanisms.