Indicate the narcotic analgesic which is a natural agonist:

Correct Answer: C

Rationale: The correct answer is C: Morphine. Morphine is a natural opioid analgesic that acts as an agonist at the mu-opioid receptors in the central nervous system, producing pain relief and sedation. It is derived from the opium poppy plant, making it a natural agonist. Meperidine (A) and Fentanyl (B) are synthetic opioids, while Naloxone (D) is an opioid antagonist used to reverse opioid overdose by blocking the effects of opioids. Therefore, the natural agonist among the options is Morphine.

Correct Answer: B

Rationale: The correct answer is B: Amitriptyline. Tricyclic antidepressants, like Amitriptyline, have a tricyclic chemical structure. They work by affecting neurotransmitters in the brain. Nefazodone (A) is a serotonin modulator, Fluoxetine (C) is an SSRI, and Isocarboxazid (D) is a monoamine oxidase inhibitor, not related to tricyclic antidepressants.

Correct Answer: B

Rationale: The correct answer is B: Sydnocarb. Sydnocarb is a CNS psychostimulant that is a sydnonymine derivative. This is because the chemical structure of Sydnocarb contains the sydnone imine group, which is characteristic of sydnonimine derivatives. A: Caffeine is not a sydnonimine derivative, as it does not contain the sydnone imine group. C: Meridil (methylphenidate hydrochloride) is not a sydnonimine derivative, as it does not contain the sydnone imine group. D: Amphetamine is not a sydnonimine derivative, as it does not contain the sydnone imine group.

Correct Answer: D

Rationale: Step 1: Psychologic dependence can involve decreased responsiveness (tolerance) to a drug due to repeated exposure. Step 2: It can also manifest as drug-specific withdrawal symptoms upon sudden discontinuation. Step 3: Additionally, psychologic dependence includes compulsive drug-seeking behavior. Step 4: Therefore, the correct answer is D, as it encompasses all these aspects of psychologic dependence. Summary: A is incorrect as it only covers tolerance, B is incorrect as it focuses solely on withdrawal symptoms, and C is incorrect as it mentions only compulsive drug-seeking behavior. The correct answer, D, includes all these components, making it the most comprehensive choice.

Correct Answer: B

Rationale: Step-by-step rationale for choice B: Thiopental: 1. Thiopental is an ultra-short-acting barbiturate commonly used as an intravenous anesthetic. 2. It has a rapid onset of action and short duration of effect, making it ideal for induction of anesthesia. 3. Its pharmacokinetics allow for quick recovery and minimal residual effects. 4. Fentanyl (choice A) is a synthetic opioid, Midazolam (choice C) is a benzodiazepine, and Ketamine (choice D) is a dissociative anesthetic, not barbiturate.