Which of the following drugs has the highest potency among the new potential inhalational anesthetics tested in laboratory animals?

Correct Answer: D

Rationale: The correct answer is D: Drug S. Potency refers to the amount of drug needed to produce a specific effect. Drug S has the highest potency among the options because it requires the smallest dose to achieve the desired effect compared to Drugs P, Q, and R. In laboratory testing, Drug S consistently showed a strong and rapid onset of action at lower doses, making it the most potent inhalational anesthetic among the options. Drug S is therefore the correct choice for having the highest potency. Choices A, B, and C are incorrect because they do not exhibit the same level of potency as Drug S based on the laboratory testing results.

Correct Answer: D

Rationale: The correct answer is D: Convulsions. Lidocaine is a local anesthetic that can cause central nervous system toxicity, leading to symptoms like seizures or convulsions. When administered near the brachial plexus for a peripheral nerve block, lidocaine can inadvertently reach systemic circulation, increasing the risk of CNS side effects. Ventricular tachycardia (A) is a cardiac adverse effect, not commonly associated with lidocaine toxicity. Abdominal colic (B) is unrelated to lidocaine administration near the brachial plexus. Drowsiness (C) is a common systemic side effect of lidocaine but is less likely to occur after administration near the brachial plexus compared to CNS effects like convulsions.

Correct Answer: B

Rationale: The correct answer is B: Vecuronium. Vecuronium is a non-depolarizing neuromuscular blocking agent that inhibits acetylcholine from binding to nicotinic receptors, leading to muscle paralysis including respiratory muscles, thus decreasing spontaneous breathing. Diazepam (A) is a benzodiazepine that acts on the central nervous system but does not directly affect respiratory muscles. Botulinum toxin (C) blocks acetylcholine release at the neuromuscular junction but is not suitable for systemic use to decrease spontaneous breathing. Dantrolene (D) is a muscle relaxant that acts on skeletal muscles but does not directly inhibit respiratory muscles.

Correct Answer: B

Rationale: The correct answer is B: Somatic nerve terminals. Botulinum toxin acts by inhibiting the release of acetylcholine at the neuromuscular junction, leading to muscle paralysis. In the context of ocular muscles in strabismus, the toxin would target the somatic nerve terminals that innervate the extraocular muscles. This action results in the relaxation of the affected muscle, helping to correct the misalignment of the eyes. Choices A, C, and D are incorrect as they do not directly relate to the mechanism of action of botulinum toxin at the neuromuscular junction.

Correct Answer: B

Rationale: The correct answer is B: Succinylcholine. Succinylcholine is a depolarizing neuromuscular blocker that causes initial muscle fasciculations followed by flaccid paralysis within minutes. This pattern of transient fasciculations progressing to generalized paralysis aligns with the patient's symptoms. Cisatracurium (A) and Vecuronium (D) are non-depolarizing neuromuscular blockers that do not typically cause fasciculations. Dantrolene (C) is a skeletal muscle relaxant used to treat malignant hyperthermia and muscle spasticity, but it does not cause the rapid progression of paralysis described in the scenario.