Which of the following CNS psychostimulants is a sydnonymine derivative?

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: 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.

Correct Answer: A

Rationale: The correct answer is A: Fenfluramine. Fenfluramine is an anorexigenic agent that affects the serotoninergic system by increasing serotonin levels, leading to appetite suppression. It works by inhibiting the reuptake of serotonin, thereby increasing its availability in the brain. This mechanism helps in reducing food intake and promoting weight loss. Other choices - B: Fepranone, C: Desopimone, and D: Masindole - do not directly affect the serotoninergic system and are not known for their anorexigenic effects. Fepranone is a beta-adrenergic agonist, Desopimone is a dopamine reuptake inhibitor, and Masindole is a monoamine oxidase inhibitor. These mechanisms are not primarily associated with appetite suppression or weight loss.

Correct Answer: A

Rationale: Tranexamic acid is structurally similar to aminocaproic acid, making it an analog. This similarity allows tranexamic acid to competitively inhibit the activation of plasminogen to plasmin, effectively reducing fibrinolysis. Therefore, the statement is TRUE. Choices B, C, and D are incorrect because tranexamic acid is indeed an analog of aminocaproic acid, making them mutually exclusive options.

Correct Answer: A

Rationale: The correct answer is A: Skeletal muscle weakness. Calcium channel blockers primarily affect smooth muscle in blood vessels and the heart, not skeletal muscles. Dizziness, headache, and flushing are common adverse effects due to vasodilation and reduced cardiac output. Therefore, the correct answer is A because skeletal muscle weakness is not a typical adverse effect of calcium channel blockers.