This drug reduces blood pressure by acting on vasomotor centers in the CNS:

Correct Answer: B

Rationale: The correct answer is B: Clonidine. Clonidine acts on vasomotor centers in the central nervous system (CNS) by stimulating alpha-2 adrenergic receptors, leading to decreased sympathetic outflow, resulting in reduced peripheral vascular resistance and ultimately lowering blood pressure. Labetalol (A) is a non-selective beta and alpha blocker, Enalapril (C) is an ACE inhibitor, and Nifedipine (D) is a calcium channel blocker, all of which work by different mechanisms to reduce blood pressure compared to Clonidine.

Correct Answer: C

Rationale: The correct answer is C: All of the above. Recombinant DNA techniques involve inserting the proinsulin gene into E. coli or yeast to produce human insulin. This is a common method used in commercial insulin production. Postmortem insulin extraction from human autopsy pancreas is also a valid source of human insulin, although it is less common due to ethical and practical considerations. Therefore, both A and B are valid sources of human insulin production, making option C the correct choice. Option D is incorrect because we have established that both A and B are valid methods for human insulin production.

Correct Answer: B

Rationale: In pharmacology, understanding the duration of action of glucocorticoids is crucial for appropriate clinical decision-making. In the context of long-acting glucocorticoids, dexamethasone stands out among the options provided (Option B). Dexamethasone has a longer half-life compared to prednisolone (Option A) and triamcinolone (Option C). This extended half-life allows for less frequent dosing, making it a preferred choice in certain conditions requiring sustained anti-inflammatory effects over an extended period. Prednisolone, while effective, is classified as an intermediate-acting glucocorticoid with a shorter duration of action compared to dexamethasone. Triamcinolone is also an intermediate-acting glucocorticoid, not falling into the category of long-acting drugs. Educationally, this question highlights the importance of knowing the pharmacokinetic profiles of different drugs within the same class. Understanding the duration of action helps healthcare providers select the most suitable therapy based on the clinical needs of the patient. This knowledge is valuable in optimizing treatment outcomes and minimizing potential adverse effects associated with inappropriate drug selection or dosing regimens.

Correct Answer: B

Rationale: Step-by-step rationale for choice B (Cyproheptadine) as the correct answer: 1. Cyproheptadine is a potent H1 receptor antagonist. 2. It is also known for its significant serotonin-blocking effect. 3. This dual mechanism of action makes it effective for treating conditions involving both histamine and serotonin imbalances. 4. Brompheniramine (A), Suprastine (C), and Dimedrol (D) do not exhibit significant serotonin-blocking effects, making them incorrect choices.

Correct Answer: A

Rationale: The correct answer is A: Extreme dryness of the conjunctiva resulting from a disease localized in the eye or from systemic deficiency of vitamin A. Xerophthalmia refers to extreme dryness of the eyes due to vitamin A deficiency. It affects the conjunctiva, leading to dry eyes. This condition can be localized in the eye or due to systemic deficiency of vitamin A. Choice B is incorrect because it describes a condition known as keratomalacia, which involves softening, ulceration, and perforation of the cornea, not extreme dryness of the conjunctiva. Choice C is also incorrect as it describes night blindness, a condition where vision is weak in dim light due to vitamin A deficiency, not extreme dryness of the conjunctiva. Choice D is incorrect because it includes all the statements, but xerophthalmia specifically refers to extreme dryness of the conjunctiva due to vitamin A deficiency, not the other conditions mentioned.