Which of the following cholinomimetics is indirect-acting?

Correct Answer: B

Rationale: The correct answer is B: Edrophonium. Edrophonium is an indirect-acting cholinomimetic agent because it works by inhibiting acetylcholinesterase enzyme, leading to an increase in acetylcholine levels at the synaptic cleft. This results in enhanced cholinergic transmission. On the other hand, choices A, C, and D are direct-acting cholinomimetics. Lobeline (A) acts as a nicotinic receptor agonist, Pilocarpine (C) is a muscarinic receptor agonist, and Carbachol (D) is a non-selective cholinomimetic that directly stimulates both nicotinic and muscarinic receptors without affecting acetylcholinesterase. Therefore, Edrophonium is the only indirect-acting cholinomimetic among the provided options.

Correct Answer: D

Rationale: The correct answer is D because epinephrine acts on different receptors to induce hyperglycemia. Epinephrine stimulates beta2 receptors to increase gluconeogenesis and glycogenolysis, leading to elevated blood glucose levels. It also inhibits insulin secretion from alpha receptors, further contributing to hyperglycemia. Therefore, all options A, B, and C are correct mechanisms through which epinephrine induces hyperglycemia.

Correct Answer: A

Rationale: The correct answer is A because phentolamine is an alpha-adrenergic antagonist that blocks presynaptic alpha2 receptors. By inhibiting these receptors, it increases norepinephrine release, leading to stimulation of unblocked beta receptors on the heart, resulting in tachycardia. This mechanism directly links the action of phentolamine to the observed tachycardia. Choice B (Baroreflex mechanism) is incorrect because phentolamine-induced tachycardia is primarily mediated by the alpha2 receptor antagonism rather than the baroreflex mechanism. Choice C (Direct effect on the heart by stimulation of beta1 receptors) is incorrect because phentolamine does not directly stimulate beta1 receptors on the heart; rather, it indirectly causes cardiac stimulation through enhanced norepinephrine release. Choice D (Inhibition of transmitter reuptake at noradrenergic synapses) is incorrect because phentolamine does not inhibit

Correct Answer: B

Rationale: The correct answer is B: Cimetidine. Cimetidine is a cytochrome P450 inhibitor that can inhibit hepatic metabolism of drugs like hypnotics, leading to increased drug levels and potential toxicity. Flumazenil (A) is a benzodiazepine receptor antagonist, not a metabolic inhibitor. Phenytoin (C) induces hepatic enzymes, increasing metabolism of other drugs. Theophylline (D) is metabolized by cytochrome P450, but it doesn't inhibit metabolism of hypnotics.

Correct Answer: D

Rationale: The correct answer is D. Phenobarbital is a barbiturate medication that can cause physical and psychological dependence, leading to addiction (Choice A). It can also exacerbate petit mal epilepsy by lowering seizure threshold (Choice B). Additionally, sedation is a common side effect of phenobarbital due to its central nervous system depressant properties (Choice C). Therefore, all of the above choices are correct, making option D the correct answer.