Xerophthalmia is:

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.

Correct Answer: D

Rationale: The correct answer is D because the metabolic products of probenecid are not uricosuric. Probenecid itself is uricosuric, meaning it promotes the excretion of uric acid from the body by inhibiting its reabsorption in the kidney tubules. Choice A is correct as probenecid does indeed promote the renal tubular secretion of penicillin. Choice B is correct as probenecid is used in the treatment of gout by lowering uric acid levels in the blood. Choice C is correct as probenecid, at appropriate doses, promotes the excretion of uric acid, thereby helping to manage conditions like gout.

Correct Answer: C

Rationale: The correct answer is C, Calcium chloride (0.68-1.36 meq calcium/mL), as it has the highest concentration of calcium per mL among the options. This makes it the most preferable for IV injection, providing a more efficient delivery of calcium to the body. Choice A, Calcium gluceptate, has a lower calcium concentration compared to Calcium chloride, making it less preferable for IV injection. Choice B, Calcium gluconate, also has a lower calcium concentration compared to Calcium chloride, making it less optimal for IV administration. Therefore, Calcium chloride is the best choice for IV injection due to its higher calcium concentration, ensuring effective calcium supplementation.

Correct Answer: C

Rationale: Metolazone acts at the distal convoluted tubule. It inhibits sodium and chloride reabsorption, leading to increased diuresis. The distal convoluted tubule is where sodium and chloride reabsorption are regulated by aldosterone. Metolazone's mechanism of action aligns with this site, making choice C the correct answer. Choices A, B, and D are incorrect because Metoljson's action is not targeted at the proximal convoluted tubule, ascending thick limb of the loop of Henle, or the collecting duct.

Correct Answer: D

Rationale: Step 1: Vancomycin is associated with pseudomembranous colitis due to disruption of normal gut flora. Step 2: Vancomycin can cause hepatotoxicity, indicated by elevated liver enzymes. Step 3: "Red neck" syndrome and phlebitis are potential adverse effects of rapid infusion. Step 4: Since all the mentioned effects are associated with vancomycin, D is the correct answer. Summary: A, B, and C are incorrect because they do not encompass all the unwanted effects of vancomycin as mentioned in the question.