Hypertensive effect of adrenaline is reversed by:

Correct Answer: C

Rationale: Step-by-step rationale: 1. Adrenaline causes vasoconstriction leading to increased blood pressure. 2. Prazosin is an alpha-1 adrenergic receptor antagonist. 3. By blocking alpha-1 receptors, prazosin reverses the vasoconstrictive effects of adrenaline. 4. Propranolol (A) is a non-selective beta-blocker and would not directly counteract adrenaline's vasoconstrictive effects. 5. Phenylephrine (B) is a vasoconstrictor itself and would further exacerbate the hypertensive effect of adrenaline. 6. Amphetamine (D) is a sympathomimetic drug that would also enhance the hypertensive effects of adrenaline. Summary: Prazosin (C) is the correct answer as it specifically targets the alpha-1 adrenergic receptors responsible for the hypertensive effects of adrenaline. Propranolol, phenylephrine, and amphetamine would

Correct Answer: C

Rationale: Rationale: C: Prazosin can block Alpha1 receptor only. - Prazosin is a selective Alpha1 blocker, mainly used for hypertension. - By blocking Alpha1 receptors, it reduces vasoconstriction and lowers blood pressure. - Prazosin does not affect Alpha2 receptors, distinguishing it from non-selective Alpha blockers. - Correct as it accurately describes Prazosin's mechanism of action. Incorrect: A: Phentolamine is a non-selective Alpha blocker, affecting both Alpha1 and Alpha2 receptors. B: Alpha2 blockers increase noradrenaline release by inhibiting the negative feedback control. D: Alpha blockers typically decrease blood pressure, but can increase heart rate due to vasodilation.

Correct Answer: B

Rationale: Step-by-step rationale for why B (Carbachol) is the correct answer: 1. Carbachol is a cholinergic drug that acts on both muscarinic and nicotinic receptors. 2. It is resistant to hydrolysis by both true and pseudo cholinesterase enzymes. 3. Acetylcholine (A) is rapidly hydrolyzed by both cholinesterases. 4. Bethanechol (C) is a muscarinic agonist but not a nicotinic agonist. 5. Succinylcholine (D) is a depolarizing neuromuscular blocking agent, not a cholinergic agonist. Summary: Carbachol is the only drug among the choices that has both muscarinic and nicotinic actions and is resistant to hydrolysis by cholinesterases. Acetylcholine is rapidly hydrolyzed, Bethanechol does not have nicotinic actions, and Succinyl

Correct Answer: D

Rationale: Pilocarpine is a parasympathomimetic agent that stimulates the muscarinic receptors in the eye, causing pupillary constriction and reducing intraocular pressure. This mechanism of action makes it effective in treating glaucoma. Heart failure (A), bronchial asthma (B), and urinary obstruction (C) are not indications for pilocarpine use based on its pharmacological properties and effects.

Correct Answer: D

Rationale: The correct answer is D. Atropine blocks the effects of cholinesterase inhibitors on muscarinic receptors but not on nicotinic receptors, which are responsible for skeletal muscle overstimulation. Atropine can block bronchoconstriction, increased bladder activity, and increased bowel motility as they are mediated by muscarinic receptors. Therefore, the effects on skeletal muscle overstimulation, leading to paralysis, will not be blocked by atropine.