Which of the following muscle relaxants would be contraindicated in a patient with a deficiency of plasma cholinesterase?

Correct Answer: A

Rationale: Tubocurarine is a non-depolarizing muscle relaxant that is metabolized by plasma cholinesterase. In a patient with a deficiency of plasma cholinesterase, tubocurarine would not be metabolized properly, leading to prolonged effects and potential toxicity. Therefore, it would be contraindicated in this patient.

Correct Answer: D

Rationale: The correct answer is D. Botulinum toxin works by inhibiting the release of acetylcholine from cholinergic terminals, leading to muscle paralysis and relaxation. This action prevents the excessive muscle contractions seen in hemifacial spasms. Inhibition of acetylcholine exocytosis from cholinergic terminals is the mechanism behind the therapeutic effect of botulinum toxin in this case.

Correct Answer: B

Rationale: Baclofen is a muscle relaxant commonly used to treat muscle spasms, making it the most appropriate choice for a patient with muscle spasms. Phenobarbital is an antiseizure medication and would not be indicated for this patient. Tubocurarine and succinylcholine are neuromuscular blocking agents used during surgery, but baclofen would be more appropriate for muscle spasms outside of surgical settings. Chlorpromazine is an antipsychotic medication and would not be indicated for muscle spasms.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.