Which of the following processes proceeds in the second phase of biotransformation?

Correct Answer: A

Rationale: The correct answer is A: Acetylation. In the second phase of biotransformation, conjugation reactions occur where a functional group is added to the drug molecule. Acetylation involves the addition of an acetyl group to the drug molecule, making it more water-soluble and easier to excrete. Reduction (B) typically occurs in the first phase, oxidation (C) can occur in both phases, and hydrolysis (D) usually occurs in the first phase as well. Therefore, acetylation is the most likely process to proceed in the second phase of biotransformation.

Correct Answer: C

Rationale: Nicotine is the correct answer because it activates both muscarinic and nicotinic receptors. Nicotinic receptors are ligand-gated ion channels found at neuromuscular junctions and autonomic ganglia. Muscarinic receptors are G-protein coupled receptors found in various tissues. Lobeline primarily acts on nicotinic receptors, pilocarpine primarily acts on muscarinic receptors, and bethanechol primarily acts on muscarinic receptors. Therefore, nicotine is the only cholinomimetic that activates both receptor types.

Correct Answer: B

Rationale: Step-by-step rationale for why B (Atropine) is the correct answer: 1. Scopolamine is an anticholinergic drug, similar to Atropine. 2. Both drugs block the action of acetylcholine at muscarinic receptors. 3. They are used for similar indications like treating motion sickness. 4. Hexamethonium is a ganglionic blocker, Succinylcholine is a depolarizing muscle relaxant, and Pilocarpine is a muscarinic agonist, making them unrelated to scopolamine's pharmacologic actions.

Correct Answer: C

Rationale: The correct answer is C: Uterus. Both alpha and beta1 adrenergic stimulation in the uterus leads to relaxation of the smooth muscle. Alpha adrenergic stimulation causes vasoconstriction in blood vessels (choice A). In the intestine (choice B), alpha adrenergic stimulation leads to decreased motility while beta1 adrenergic stimulation increases heart rate in bronchial muscles (choice D). Thus, the uterus is the only tissue where both alpha and beta1 adrenergic stimulation have the same effect of muscle relaxation.

Correct Answer: D

Rationale: Step-by-step rationale for why Phenoxybenzamine (choice D) is the correct answer: 1. Phenoxybenzamine is an irreversible alpha receptor antagonist, blocking alpha-1 and alpha-2 receptors. 2. It forms covalent bonds with the receptors, leading to long-lasting and irreversible blockade. 3. This irreversible binding distinguishes Phenoxybenzamine from reversible alpha blockers like Prazosin (choice C). 4. Tolazoline (choice A) is a nonselective alpha blocker, and Labetalol (choice B) is a mixed alpha and beta blocker, but neither are irreversible. Summary: Phenoxybenzamine is the correct choice as it irreversibly blocks alpha receptors, unlike the other options which are either nonselective or reversible blockers.