Half-life of OKT-3 is:

Correct Answer: A

Rationale: The correct answer is A: 18-24 hours. The half-life of a drug is the time it takes for half of the drug to be removed from the body. OKT-3 has a relatively short half-life, typically ranging from 18 to 24 hours. This means that after 18-24 hours, only half of the initial dose of OKT-3 will remain in the body. Choice B (25-35 minutes) is too short for a drug like OKT-3 which is used for immunosuppression and requires a longer duration of action. Choice C (4-16 hours) falls within the correct range but is not as specific as the 18-24 hours range. Choice D (21 days) is too long for OKT-3, as drugs with such long half-lives are typically not used for immunosuppression due to the difficulty in adjusting dosages.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Bile acid-binding resins can bind to various drugs and vitamins in the gastrointestinal tract, leading to reduced absorption. This occurs due to the resins' ability to form complexes with these substances, preventing their uptake into the bloodstream. This interference can potentially impact the effectiveness of medications or the absorption of essential vitamins. Choices B, C, and D are incorrect because they do not accurately reflect the specific mechanism of action of bile acid-binding resins in drug and vitamin absorption.

Correct Answer: A

Rationale: The correct answer is A: Hepatic toxicity. Dihydrotachysterol is a vitamin D analog used to treat hypoparathyroidism and hypocalcemia. It can cause liver damage as a side effect due to its metabolism in the liver. General malaise (B), lymphocytopenia (C), and hypertension (D) are not typically associated with dihydrotachysterol use. Therefore, the correct answer is A based on the drug's mechanism of action and known side effects.

Correct Answer: C

Rationale: Rationale: Chronic use of Furosemide can lead to distal tubular hypertrophy, reducing its diuretic effect due to compensatory changes in the nephron function. Furosemide is a loop diuretic acting in the thick ascending limb of the loop of Henle. Acetazolamide is a carbonic anhydrase inhibitor acting in the proximal tubule. Amiloride is a potassium-sparing diuretic acting on the collecting duct. Hydrochlorothiazide is a thiazide diuretic acting in the distal convoluted tubule. Only Furosemide among the options affects the loop of Henle, leading to distal tubular hypertrophy over time.

Correct Answer: B

Rationale: The correct answer is B: Lincomycin. Lincomycin belongs to the lincosamides class of antibiotics, which also includes clindamycin. Lincomycin works by inhibiting bacterial protein synthesis. Erythromycin (A) is a macrolide antibiotic, not a lincosamide. Azithromycin (C) is another macrolide antibiotic. Aztreonam (D) is a monobactam antibiotic, not a lincosamide. Therefore, the correct answer is B because it is the only drug belonging to the lincosamides class.