Select the narcotic analgesic which is an antagonist or partial mu receptor agonist:

Correct Answer: B

Rationale: The correct answer is B: Pentazocine. Pentazocine is a mixed opioid receptor agonist-antagonist, acting as a partial agonist at the mu receptor and antagonist at the kappa receptor. This dual mechanism provides analgesia with less risk of respiratory depression compared to full mu agonists like Fentanyl, Codeine, and Methadone. Fentanyl (A) is a potent mu agonist, Codeine (C) is a prodrug that is metabolized to morphine, a full mu agonist, and Methadone (D) is a full mu agonist used for opioid addiction treatment. By understanding the pharmacological properties of these drugs, we can determine that Pentazocine is the only correct choice.

Correct Answer: D

Rationale: The correct answer is D, Fluoxetine. Second-generation heterocyclic drugs refer to selective serotonin reuptake inhibitors (SSRIs), which include fluoxetine. SSRIs are considered second-generation due to their improved safety and tolerability compared to first-generation heterocyclic drugs like tricyclic antidepressants (e.g., imipramine and maprotiline). Phenelzine is a monoamine oxidase inhibitor (MAOI), not a heterocyclic drug. Imipramine and maprotiline are tricyclic antidepressants, falling under the first-generation category. Therefore, the correct choice is D as it fits the criteria for a second-generation heterocyclic drug.

Correct Answer: A

Rationale: Step-by-step rationale for the correct answer (A): Sydnocarb is a stimulant drug known to decrease fatigue, enhance professional work performance, and combat drowsiness. This aligns with the statement in choice A. The drug does not induce feelings of prosperity, relaxation, or euphoria (choice B), as it is not a psychoactive substance. Sydnocarb does not cause an influx of physical and mental forces or excitation of locomotive and speech (choice C), as it primarily targets fatigue and alertness. Additionally, Sydnocarb does not exhibit peripheral sympathomimetic action (choice D), which involves mimicking the effects of the sympathetic nervous system on peripheral organs.

Correct Answer: D

Rationale: The correct answer is D because tolerance involves multiple mechanisms. A is correct because tolerance can involve compensating for the drug effect. B is correct because chronic use can lead to increased drug disposition. C is correct because tolerance can result from changes in receptors, enzymes, or membrane actions. Therefore, all of the above (A, B, and C) are associated with tolerance, making option D the correct answer. Each option individually addresses a different aspect of tolerance mechanisms, making them incorrect as standalone choices.

Correct Answer: A

Rationale: Step 1: Identify benzodiazepine derivatives - Midazolam is a benzodiazepine derivative used as an intravenous anesthetic. Step 2: Eliminate other options - Thiopental is a barbiturate, Ketamine is a dissociative anesthetic, and Propofol is a sedative-hypnotic. Step 3: Verify knowledge - Benzodiazepines like Midazolam act on GABA receptors, producing sedative and anxiolytic effects. Step 4: Confirm choice - Midazolam's pharmacological profile aligns with a benzodiazepine derivative used for anesthesia. Summary: Midazolam (A) is the correct answer as it is a benzodiazepine derivative, while the other choices (B, C, D) represent different classes of intravenous anesthetics.