Barbiturates are being replaced by hypnotic benzodiazepines because of:

Correct Answer: D

Rationale: The correct answer is D: All of the above. Barbiturates have a low therapeutic index, leading to a narrow range between therapeutic and toxic doses. They suppress REM sleep, which can lead to negative effects on sleep quality. Barbiturates also have a high potential for physical dependence and abuse, making them less desirable compared to benzodiazepines. Therefore, all the given reasons collectively contribute to the shift towards using hypnotic benzodiazepines over barbiturates.

Correct Answer: D

Rationale: The correct answer is D: All of the above. In the antinociceptive descending pathways, multiple endogenous opioids play a role in pain modulation. Beta-endorphin, met- and leu-enkephalin, and dynorphin all act as chemical mediators to inhibit pain signals. Each of these opioids bind to different opioid receptors in the central nervous system, contributing to the overall analgesic effect. Therefore, the correct answer includes all three options as they collectively participate in the antinociceptive pathways. Choices A, B, and C alone are not sufficient to fully explain the complexity of the pain modulation system, making option D the most comprehensive and accurate choice.

Correct Answer: D

Rationale: The correct answer is D: Acetaldehyde. Disulfiram inhibits the enzyme aldehyde dehydrogenase, leading to accumulation of acetaldehyde when alcohol is consumed. Acetaldehyde buildup causes unpleasant symptoms like flushing, nausea, and headache. Formaldehyde (A) is not directly related to this interaction. Acetate (B) is a product of alcohol metabolism, not affected by disulfiram. Formic acid (C) is associated with methanol toxicity, not disulfiram-alcohol reaction. Therefore, the correct answer is D, as it aligns with the mechanism of action of disulfiram.

Correct Answer: C

Rationale: The correct answer is C: Haloperidol. Haloperidol is preferable in patients with coronary and cerebrovascular disease due to its lower risk of causing cardiovascular adverse effects compared to the other options. Chlorpromazine (A) can cause orthostatic hypotension and prolong QT interval. Fluphenazine (B) can lead to QT prolongation and hypotension. Perphenazine (D) also carries a risk of QT prolongation and orthostatic hypotension. In contrast, Haloperidol has a more favorable cardiovascular safety profile, making it the preferred choice for patients with coronary and cerebrovascular disease.

Correct Answer: A

Rationale: The correct answer is A: Meridil. Psychostimulants are substances that can increase alertness, attention, and energy levels. Meridil, also known as methylphenidate, is a commonly prescribed psychostimulant used to treat conditions like ADHD. Camphor (B) is a topical analgesic, Piracetam (C) is a nootropic agent, and Pantocrin (D) is a herbal supplement with purported energy-boosting properties. Therefore, only Meridil (A) fits the classification of a psychostimulant among the choices provided.