Which of the following drugs has “double-acetylcholine” structure?

Correct Answer: D

Rationale: The correct answer is D: Succinylcholine. Succinylcholine has a "double-acetylcholine" structure because it contains two acetylcholine molecules linked together. This structure allows succinylcholine to act as a depolarizing neuromuscular blocker by mimicking the action of acetylcholine at the neuromuscular junction. Rocuronium (A) and Atracurium (C) are nondepolarizing neuromuscular blockers that do not have a double-acetylcholine structure. Carbachol (B) is a cholinergic agonist but does not have a double-acetylcholine structure like succinylcholine.

Correct Answer: D

Rationale: The correct answer is D because the statement that the ALFA1a subtype mediates both vascular and prostate smooth muscle contraction is incorrect. The ALFA1a subtype primarily mediates prostate smooth muscle contraction, while the ALFA1b subtype is responsible for vascular smooth muscle contraction. This is a key distinction in understanding the roles of different subtypes of alfa1 receptors. Choices A, B, and C are all correct statements as there are indeed at least three subtypes of alfa1 receptors (alfa1a, alfa1b, and alfa1d), ALFA1a subtype does mediate prostate smooth muscle contraction, and ALFA1b subtype does mediate vascular smooth muscle contraction, respectively.

Correct Answer: C

Rationale: Flumazenil is a benzodiazepine receptor antagonist that reverses the effects of benzodiazepines like zolpidem, making choice C correct. Flumazenil does not block the actions of phenobarbital (choice A) or morphine (choice B) as they act on different receptors. Ethanol (choice D) is not affected by flumazenil. In summary, flumazenil specifically antagonizes benzodiazepines like zolpidem, making other choices incorrect.

Correct Answer: A

Rationale: The correct answer is A: Gastrointestinal reactions, such as anorexia, pain, nausea, and vomiting. Ethosuximide is primarily used to treat absence seizures. Its common side effects include gastrointestinal reactions due to its irritant effect on the gastric mucosa. Anorexia, pain, nausea, and vomiting are commonly reported adverse effects. Exacerbated grand mal epilepsy (choice B) is not a known adverse effect of ethosuximide. Transient lethargy or fatigue (choice C) is a common side effect, but it is not dose-related. Therefore, the correct answer is A, as it accurately reflects the dose-related adverse effect of ethosuximide, while the other choices do not.

Correct Answer: D

Rationale: The correct answer is D: Trihexyphenidyl. Trihexyphenidyl is an anticholinergic drug that can worsen glaucoma by causing pupil dilation, leading to increased intraocular pressure. This can exacerbate the condition and potentially cause vision problems. Selegiline (A) is a monoamine oxidase inhibitor used in Parkinson's disease but does not affect glaucoma. Levodopa (B) is a gold standard treatment for Parkinson's and does not directly impact glaucoma. Bromocriptine (C) is a dopamine agonist used in Parkinson's but does not have a significant effect on glaucoma. Thus, the correct choice to avoid in patients with glaucoma is Trihexyphenidyl due to its potential to worsen the condition.