Treatment with selegilin postpones the need for levodopa for 3-9 months and may retard the progression of Parkinson′s disease.

Correct Answer: A

Rationale: 1. Selegiline is a monoamine oxidase-B inhibitor that can delay the need for levodopa by inhibiting dopamine breakdown. 2. Studies have shown that selegiline can postpone the need for levodopa by 3-9 months. 3. By delaying levodopa initiation, selegiline may slow down the progression of Parkinson's disease. 4. Therefore, the statement that treatment with selegiline postpones the need for levodopa and may retard disease progression is true. Summary: B is incorrect because evidence supports the efficacy of selegiline in delaying levodopa use. C is incorrect as there is a clear correct answer. D is incorrect as not all options are correct, only option A is supported by evidence.

Correct Answer: A

Rationale: The correct answer is A because phenothiazine derivatives exert their strong antiemetic effect by blocking dopamine receptors in the chemoreceptor trigger zone of the medulla. This area is responsible for initiating the vomiting reflex. By blocking dopamine receptors here, phenothiazines prevent the activation of the vomiting reflex. Choices B and C are incorrect because phenothiazines primarily target the chemoreceptor trigger zone in the medulla, not the receptors in the stomach or the medullar vomiting centre. Choice D is also incorrect because the antiemetic effect is specifically due to dopamine receptor blockade in the chemoreceptor trigger zone, not all of the above options.

Correct Answer: D

Rationale: The main claim for an ideal antidepressant agent should encompass all aspects mentioned in the choices. A faster onset of action ensures quicker relief for the patient. Fewer adverse effects reduce the burden on the patient. Lower toxicity in overdoses enhances safety. Therefore, D is correct as it combines these essential criteria for an ideal antidepressant. Options A, B, and C individually address important factors but do not cover the comprehensive requirements of an ideal antidepressant, making them incorrect.

Correct Answer: A

Rationale: The correct answer is A: Triazolam. Triazolam has a short duration of action due to its rapid onset and short half-life. It is commonly used for the treatment of insomnia. Clorazepate (B), Prazepam (C), and Clordiazepoxide (D) have longer durations of action compared to Triazolam. Clorazepate is a long-acting benzodiazepine used for anxiety disorders, Prazepam is an intermediate-acting benzodiazepine, and Clordiazepoxide is a long-acting benzodiazepine used for alcohol withdrawal and anxiety. Triazolam's rapid onset and short duration make it suitable for managing acute insomnia.

Correct Answer: A

Rationale: The correct answer is A: Benzodiazepines. They are the drugs of choice for reversing withdrawal syndromes due to their ability to target the central nervous system and alleviate symptoms by acting on GABA receptors. Benzodiazepines help to reduce anxiety, seizures, and other withdrawal symptoms effectively. Neuroleptics (choice B) are not typically recommended for treating withdrawal symptoms as they may worsen certain symptoms. Antidepressants (choice C) are not the first-line treatment for reversing withdrawal syndromes as they mainly target mood disorders. Choice D is incorrect because not all the options are drugs of choice for reversing withdrawal syndromes.