Which of the following sympathomimetics is not a catecholamine:

Correct Answer: C

Rationale: The correct answer is C: Amphetamine. Amphetamine is not a catecholamine because it is a synthetic drug, not naturally produced by the body like adrenaline (A), noradrenaline (B), and isoprenaline (D). Catecholamines are a class of neurotransmitters that include dopamine, adrenaline, and noradrenaline, all of which have a catechol group in their chemical structure. Amphetamine, on the other hand, is a substituted phenethylamine with no catechol group. This distinction makes amphetamine the only non-catecholamine among the given options.

Correct Answer: B

Rationale: The correct answer is B: Trimetaphan. Nicotinic receptors are blocked by non-depolarizing neuromuscular blockers like Trimetaphan. Propranolol (A) is a beta-blocker, Prazosin (C) is an alpha-1 blocker, and Pilocarpine (D) is a muscarinic agonist, none of which block nicotinic receptors. Therefore, Trimetaphan (B) is the only choice that directly blocks nicotinic receptors.

Correct Answer: D

Rationale: Selective beta2 stimulants typically cause skeletal muscle tremors due to their action on beta2 receptors in skeletal muscles. They can also lead to tolerance with prolonged use, requiring higher doses for the same effect. Additionally, they can cause tachycardia by stimulating beta2 receptors in the heart. Therefore, all of the above choices (A, B, and C) are correct.

Correct Answer: D

Rationale: The correct answer is D, Edrophonium. Edrophonium is a short-acting cholinesterase inhibitor used in the diagnosis of myasthenia gravis. It does not possess muscarinic blocking activity, as its mechanism of action involves inhibition of acetylcholinesterase leading to increased acetylcholine levels at the neuromuscular junction. The other choices, Amitriptyline (A) is a tricyclic antidepressant with anticholinergic properties, Meperidine (B) has weak antimuscarinic effects, and Ipratropium (C) is an anticholinergic medication used in respiratory conditions. These choices exhibit muscarinic blocking activity, unlike Edrophonium.

Correct Answer: A

Rationale: The correct answer is A: Stimulation of beta adrenergic receptors. Propranolol is a beta-blocker that works by blocking beta adrenergic receptors, not stimulating them. Blocking these receptors leads to decreased heart rate, reduced cardiac contractility, and lowered blood pressure. Choices B, C, and D are incorrect because propranolol actually blocks beta adrenergic receptors, depresses cardiac contractility, and decreases blood pressure, respectively.