Which of the following antidepressants is an unselective MAO blocker and produces extremely long-lasting inhibition of the enzyme?

Correct Answer: B

Rationale: The correct answer is B: Tranylcypramine. Tranylcypramine is an unselective MAO blocker, inhibiting both MAO-A and MAO-B, leading to long-lasting enzyme inhibition. Moclobemide (A) is a reversible MAO-A inhibitor. Selegiline (C) is a selective MAO-B inhibitor. Fluoxetine (D) is a selective serotonin reuptake inhibitor (SSRI) and does not inhibit MAO enzymes. Therefore, Tranylcypramine is the correct choice for producing long-lasting MAO inhibition.

Correct Answer: B

Rationale: The correct answer is B: More addictive and fast-acting. Heroin is derived from morphine and is more potent, leading to a faster onset of action and increased addictive potential. The rapid crossing of the blood-brain barrier contributes to its fast-acting properties. It is crucial to differentiate between heroin and morphine due to their varying addictive nature and speed of action. Choices A, C, and D are incorrect because heroin is not typically used clinically, is not more effective orally, and is actually more potent and faster-acting than morphine, making it not less potent and long-acting.

Correct Answer: B

Rationale: Step 1: Ketamine is the correct choice for dissociative anesthesia due to its unique mechanism of action, which involves blocking NMDA receptors, leading to dissociation of sensory input from conscious perception. Step 2: Midazolam (A) is a benzodiazepine used for sedation and anxiolysis, not dissociative anesthesia. Step 3: Fentanyl (C) is an opioid analgesic used for pain control, not dissociative anesthesia. Step 4: Thiopental (D) is a barbiturate used for induction of general anesthesia, not specifically for dissociative anesthesia.

Correct Answer: D

Rationale: The correct answer is D: Apomorphine hydrochloride. Apomorphine hydrochloride is not an antiemetic; it is a dopamine agonist primarily used to treat Parkinson's disease. Metoclopramide, Ondansetron, and Chlorpromazine are all antiemetic drugs that work by different mechanisms to alleviate nausea and vomiting. Metoclopramide acts as a dopamine antagonist and 5-HT3 receptor antagonist, Ondansetron is a selective 5-HT3 receptor antagonist, and Chlorpromazine is a dopamine antagonist with antiemetic properties. Therefore, D is the correct answer as it does not belong to the class of antiemetic drugs.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Sugar molecules in glycosides can affect cardiotonic action by enhancing heart function, impact pharmacokinetic properties by influencing drug absorption and metabolism, and contribute to toxic properties by affecting bioavailability and toxicity. Therefore, all the options (A, B, C) are influenced by sugar molecules in glycosides.