Which of the following local anesthetics is a thiophene derivative?

Correct Answer: B

Rationale: The correct answer is B: Ultracaine. Ultracaine is a thiophene derivative because it contains a thiophene ring in its chemical structure. Thiophene is a five-membered heterocyclic compound containing sulfur. Procaine (A) is an ester local anesthetic, Lidocaine (C) is an amide local anesthetic, and Mepivacaine (D) is an amide local anesthetic. Therefore, they do not belong to the thiophene derivative class. Ultracaine is the only option that fits the description of being a thiophene derivative.

Correct Answer: C

Rationale: Hexamethonium is a ganglionic blocker that acts specifically at the autonomic ganglia. It inhibits the action of acetylcholine at the ganglionic nicotinic receptors, leading to the blockade of autonomic functions. This results in the inhibition of sympathetic and parasympathetic responses. Therefore, the correct answer is C: Autonomic ganglia. Muscarinic receptor site (A) is not directly affected by Hexamethonium. Neuromuscular junction (B) is not the primary site of action for this drug. Axonal transmission (D) is not the specific target of Hexamethonium.

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.