Which of the following opioid analgesics induces withdrawal syndrome when given to a morphine addict:

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: 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.

Correct Answer: A

Rationale: Diclofenac (choice A) concentrates in synovial fluid, enhancing its efficacy in joint inflammation (e.g., arthritis). Aspirin (choice B) and Acetaminophen (choice D) don't target synovial fluid significantly. Codeine (choice C), an opioid, lacks anti-inflammatory action. Diclofenac's pharmacokinetics suit musculoskeletal conditions.

Correct Answer: A

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