Which of the following drugs would be most appropriate for this patient to substitute for valproic acid therapy?

Correct Answer: A

Rationale: The correct answer is A: Carbamazepine. This is because carbamazepine is commonly used as an alternative to valproic acid due to its similar efficacy in treating certain types of seizures. Carbamazepine is also effective in treating bipolar disorder, which may be a reason for switching from valproic acid. Clonazepam (B) and phenytoin (C) are not appropriate substitutes for valproic acid as they have different mechanisms of action and are used for different types of seizures. Ethosuximide (D) is primarily used for absence seizures and would not be a suitable substitute for valproic acid in this case.

Correct Answer: B

Rationale: The correct answer is B: Levodopa. Levodopa is a common medication used to treat Parkinson's disease. The symptoms described by the patient, such as facial grimacing, lip smacking, and rocking of the trunk, are characteristic of levodopa-induced dyskinesias, which can occur as a side effect of long-term levodopa therapy. Levodopa-induced dyskinesias usually develop after 1-2 hours of taking the medication, as seen in this case. Choice A: Selegiline is a selective MAO-B inhibitor and is less likely to cause the described adverse effects compared to levodopa. Choice C: Entacapone is a catechol-O-methyltransferase (COMT) inhibitor used in combination with levodopa, but it is not known to cause the specific dyskinesias described. Choice D: Amantadine is an antiviral agent with antiparkinsonian effects, but it is

Correct Answer: B

Rationale: The correct answer is B: Decreased acetylcholine release from cholinergic terminals. Acetylcholine release from cholinergic terminals contributes to the parasympathetic response, which can cause adverse effects such as bradycardia. By decreasing acetylcholine release, the parasympathetic response is reduced, leading to a more balanced autonomic control of the heart rate. Activation of cardiac dopamine receptors (choice A) and β receptors (choice C) would usually have positive effects on the heart, while blockade of cardiac M receptors (choice D) would exacerbate the adverse effects by blocking the already decreased parasympathetic response.

Correct Answer: D

Rationale: The correct answer is D: Clozapine. Clozapine is the most appropriate choice for a 29-year-old man with chronic paranoid schizophrenia at this stage due to its efficacy in treatment-resistant cases and lower risk of extrapyramidal side effects. It is often considered a last resort due to its potential side effects, such as agranulocytosis, which requires regular monitoring. A: Fluphenazine and B: Thioridazine are typical antipsychotics with a higher risk of extrapyramidal side effects and are less effective in treatment-resistant cases compared to Clozapine. C: Fluoxetine is an antidepressant and not typically used as a first-line treatment for schizophrenia. It is more commonly used for depressive symptoms that may co-occur with schizophrenia.

Correct Answer: C

Rationale: The correct answer is C: Haloperidol. The patient's syndrome is most likely caused by Haloperidol, an antipsychotic drug known to cause extrapyramidal symptoms such as dystonia, akathisia, and parkinsonism. Imipramine (A) is a tricyclic antidepressant associated with anticholinergic effects. Temazepam (B) is a benzodiazepine used for insomnia. Fluoxetine (D) is a selective serotonin reuptake inhibitor used for depression and not typically associated with extrapyramidal symptoms. Therefore, the most likely culprit is Haloperidol due to its known side effect profile.