Vitamin-like compounds are:

Correct Answer: A

Rationale: The correct answer is A because vitamin-like compounds are a group of compounds that are essential for health but are not classified as vitamins. These compounds have specific roles in the body, particularly during periods of rapid growth and development. They are not inorganic nutrients (B) or organic substances needed in large quantities (C). They are also not products of endocrine gland secretion (D). The key is to understand that vitamin-like compounds are essential for certain stages of development and growth, making choice A the most appropriate answer.

Correct Answer: D

Rationale: Gemfibrozil (Lopid) increases lipoprotein lipase (LPL) activity in adipose tissue. Firstly, it is a fibric acid derivative that specifically targets LPL, leading to increased breakdown of triglyceride-rich lipoproteins. This mechanism helps lower triglyceride levels in the blood. Cholestyramine (A) is a bile acid sequestrant that does not affect LPL activity. Lovastatin (B) is a statin that primarily works by inhibiting cholesterol synthesis in the liver. Nicotinic acid (C) mainly acts by reducing circulating levels of LDL cholesterol and triglycerides, not by enhancing LPL activity.

Correct Answer: D

Rationale: Step-by-step rationale for the correct answer (D): 1. Pamidronate is a bisphosphonate used to treat conditions involving excessive bone breakdown. 2. Hypercalcemia is a condition characterized by elevated calcium levels in the blood. 3. Pamidronate works by inhibiting bone resorption, which helps lower blood calcium levels in hypercalcemia. 4. Therefore, the indication for pamidronate administration is hypercalcemia. Summary of other choices: A: Failure of vitamin D formation in skin - Not related to pamidronate use. B: Hypoparathyroidism - Pamidronate is not indicated for hypoparathyroidism. C: Elevated skeletal turnover - While pamidronate is used for conditions involving high skeletal turnover, hypercalcemia is the primary indication for its administration.

Correct Answer: D

Rationale: The correct answer is D: Carbonic anhydrase inhibitors. These drugs act at the proximal tubule by inhibiting the enzyme carbonic anhydrase, which leads to decreased reabsorption of bicarbonate and sodium. This results in increased urinary excretion of bicarbonate and sodium, leading to diuresis. Loop diuretics (A) act at the thick ascending limb of the loop of Henle, thiazide diuretics (B) act at the distal convoluted tubule, and potassium-sparing diuretics (C) act at the collecting duct. Therefore, choices A, B, and C are incorrect as they do not target the proximal tubule.

Correct Answer: A

Rationale: The correct answer is A: Penicillin G. This is because Penicillin G has a shorter duration of action compared to the other choices. B, C, and D are all forms of long-acting penicillin preparations designed for sustained release over an extended period. Penicillin G, on the other hand, is a short-acting formulation that requires more frequent dosing due to its rapid elimination from the body. Therefore, Penicillin G does not demonstrate a prolonged effect like the other options.