Allergic reaction is:

Correct Answer: A

Rationale: The correct answer is A. Allergic reaction is a response of the immune system to an allergen that the body has previously been sensitized to. This response can be local or generalized, involving various symptoms such as itching, hives, swelling, and in severe cases, anaphylaxis. Choice B describes inflammation, not specifically related to allergies. Choices C and D are unrelated medications. In summary, choice A is correct because it accurately defines an allergic reaction, while the other choices do not specifically address the nature of allergies.

Correct Answer: B

Rationale: Selegiline is the correct answer as it is a monoamine oxidase (MAO) inhibitor. MAO inhibitors block the breakdown of monoamine neurotransmitters such as dopamine, serotonin, and norepinephrine. Physostigmine is an acetylcholinesterase inhibitor, not an MAO inhibitor. Acetazolamide is a carbonic anhydrase inhibitor used in glaucoma and altitude sickness. Disulfiram is an aldehyde dehydrogenase inhibitor used in alcohol aversion therapy.

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.