A 53-year-old man with schizophrenia presents to his primary care physician for follow-up. He has been treated with multiple different antipsychotic agents during his lifetime. Which of the following antipsychotic agents has the highest affinity for the \(D_2\) receptors?

Correct Answer: D

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

Correct Answer: C

Rationale: Nalbuphine (choice C), a mixed agonist-antagonist (kappa agonist, mu antagonist), can precipitate withdrawal in morphine addicts by antagonizing mu receptors, displacing morphine and reversing its effects, causing symptoms like anxiety and sweating. Meperidine (choice A), Methadone (choice B), and Fentanyl (choice D), all full mu agonists, maintain opioid effects, not inducing withdrawal unless stopped abruptly. Nalbuphine's antagonistic action at mu receptors in dependent patients makes it the correct choice. This highlights the importance of receptor pharmacology in managing opioid-dependent patients, avoiding unintended withdrawal.

Correct Answer: A

Rationale: Buspirone (choice A) is an anxiolytic acting as a partial agonist at 5-HT1A serotonin receptors, reducing anxiety without sedation, unlike benzodiazepines. Flurazepam (choice B) and Diazepam (choice C) enhance GABAa effects, not serotonin. Chloral hydrate (choice D), a sedative, lacks receptor specificity. Buspirone's unique mechanism avoids dependence, making it distinct in anxiety treatment.

Correct Answer: A

Rationale: Aminophylline, a methylxanthine, bronchodilates (choice D), acts as a diuretic (choice B), and stimulates respiration (choice C) via phosphodiesterase inhibition and adenosine antagonism. It increases cardiac output, not decreases it (choice A), by enhancing contractility and heart rate. This exception reflects its cardiovascular stimulation, key in asthma therapy.

Correct Answer: B

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