Indicate the mechanism of barbiturate action (at hypnotic doses):

Correct Answer: D

Rationale: The correct answer is D because barbiturates act by increasing the duration, frequency, and direct activation of GABA-gated Cl- channels. This leads to hyperpolarization of neurons, resulting in sedative and hypnotic effects. Choice A is correct as barbiturates prolong the opening of Cl- channels. Choice B is incorrect as barbiturates enhance, not directly activate, the Cl- channels. Choice C is incorrect as barbiturates increase the duration, not frequency, of Cl- channel opening events. Therefore, the correct answer is D as it encompasses all the mechanisms of barbiturate action.

Correct Answer: C

Rationale: Rationale: 1. Tolcapone inhibits catechol-O-methyltransferase (COMT), reducing levodopa peripheral metabolism. 2. By prolonging levodopa's action, it enhances its efficacy in treating Parkinson's disease. 3. Carbidopa enhances levodopa bioavailability, not directly affecting its peripheral metabolism. 4. Clozapine is an antipsychotic with no COMT inhibitory activity. 5. Rasagiline is a monoamine oxidase-B inhibitor, not a COMT inhibitor.

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.