The main reason for using alfa-receptor antagonists in the management of pheochromocytoma is:

Correct Answer: B

Rationale: The correct answer is B because alpha-receptor antagonists block alpha2 receptors on vascular smooth muscle, preventing vasoconstriction caused by epinephrine and reducing blood pressure in patients with pheochromocytoma. This helps manage symptoms of hypertension and tachycardia associated with excessive catecholamine release. Incorrect choices: A: Alpha-receptor antagonists do not inhibit the release of epinephrine from the adrenal medulla. C: Alpha-receptor antagonists do not interact with or inhibit beta2 adrenoreceptors. D: Alpha-receptor antagonists do not antagonize the release of renin.

Correct Answer: C

Rationale: The correct answer is C, Lamotrigine. Lamotrigine is a phenyltriazine derivative, making it the antiseizure drug in the list. This drug works by stabilizing neuronal membranes and inhibiting voltage-gated sodium channels. Phenobarbital (A) is a barbiturate, Clonazepam (B) is a benzodiazepine, and Carbamazepine (D) is an iminostilbene derivative, not a phenyltriazine derivative like Lamotrigine.

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 moderate alcohol consumption has been shown to raise serum levels of high-density lipoproteins (HDL), also known as "good" cholesterol. HDL helps remove other forms of cholesterol from the bloodstream, reducing the risk of cardiovascular disease. Increased HDL levels are associated with a lower risk of heart disease. On the other hand, choices B, C, and D are incorrect. Choice B, increasing low-density lipoproteins (LDL), is not a typical effect of moderate alcohol consumption and is associated with an increased risk of heart disease. Choice C, decreasing HDL levels, contradicts the known positive effect of alcohol on HDL. Choice D, raising very low-density lipoproteins (VLDL), is not a common result of moderate alcohol intake and is typically associated with an increased risk of heart disease.

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.