The mechanism of vigabatrin′s action is:

Correct Answer: B

Rationale: The correct answer is B: Inhibition of GABA aminotransferase. Vigabatrin increases GABA levels by inhibiting GABA aminotransferase enzyme, which is responsible for GABA breakdown. This leads to enhanced GABAergic inhibition in the brain. A: Direct action on the GABA receptor-chloride channel complex is incorrect as vigabatrin does not directly bind to GABA receptors. C: NMDA receptor blockade via the glycine binding site is incorrect as vigabatrin does not affect NMDA receptors. D: Inhibition of GABA neuronal reuptake from synapses is incorrect as vigabatrin does not affect GABA reuptake mechanisms.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Alcohol potentiates SNS depressants by enhancing their sedative effects, vasodilators by causing further relaxation of blood vessels, and hypoglycemic agents by lowering blood sugar levels. This occurs due to alcohol's ability to enhance the effects of these substances, leading to increased sedation, blood vessel dilation, and blood sugar reduction when combined. Therefore, choosing any of the other options would be incorrect as they do not encompass the full range of substances that alcohol can potentiate.

Correct Answer: D

Rationale: Phenothiazine derivatives like chlorpromazine possess antihistaminic, anticholinergic, and antidopaminergic activities. These properties make them effective in treating various conditions like schizophrenia. Antihistaminic activity helps with sedation, anticholinergic activity reduces side effects like tremors, and antidopaminergic activity helps manage psychotic symptoms. Therefore, the correct answer is D. Choices A, B, and C are incorrect because phenothiazines typically exhibit a combination of all three activities, not just one.

Correct Answer: A

Rationale: The correct answer is A: Amitriptyline. Amitriptyline is a tricyclic antidepressant that can worsen symptoms in patients with prostatic hypertrophy, glaucoma, coronary, and cerebrovascular disease due to its anticholinergic effects. It can cause urinary retention in prostatic hypertrophy, increase intraocular pressure in glaucoma, and exacerbate cardiovascular conditions. Paroxetine, Bupropion, and Fluoxetine are generally safer options as they have less anticholinergic effects and are less likely to exacerbate these conditions.

Correct Answer: D

Rationale: The correct answer is D, all of the above. Anxiolytic dosage reduction is recommended in patients taking cimetidine due to potential drug interactions. In patients with hepatic dysfunction, reduced metabolism can lead to increased drug levels. Elderly patients may be more sensitive to anxiolytics due to age-related changes in metabolism and increased risk of adverse effects. Therefore, all three factors (cimetidine use, hepatic dysfunction, and age) can influence anxiolytic dosing, making D the correct choice.