Which of the following local anesthetics would be appropriate for a pregnant woman with a history of anaphylactic reaction to para-aminobenzoic acid?

Correct Answer: C

Rationale: Lidocaine would be the most appropriate choice for a pregnant woman with a history of anaphylactic reaction to para-aminobenzoic acid (PABA). Lidocaine is an amide local anesthetic that does not contain PABA and is less likely to trigger an allergic reaction in individuals sensitive to this compound. It is important to choose a local anesthetic that is safe for the patient and avoids any potential allergic responses.

Correct Answer: B

Rationale: Botulinum toxin primarily acts at somatic nerve terminals by blocking the release of acetylcholine, leading to muscle paralysis. In the context of strabismus treatment, the toxin targets the nerve terminals supplying the extrinsic ocular muscles, specifically affecting neuromuscular transmission at the neuromuscular junction. This action results in localized muscle weakness and temporary paralysis, aiding in the correction of strabismus.

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: B

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

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.