What is the mechanism that allows mannitol to produce diuresis?

Correct Answer: D

Rationale: The correct answer is D because mannitol is an osmotic diuretic that increases the osmolarity of plasma. This high osmolarity creates an osmotic pressure gradient that pulls water out of the tissues into the bloodstream, leading to increased urine production. Choice A is incorrect because mannitol does not compete with aldosterone for cellular receptor sites. Choice B is incorrect because mannitol primarily works in the proximal tubule, not the loop of Henle. Choice C is incorrect because mannitol does not interfere with the absorption of sodium ions across the distal renal tubule.

Correct Answer: A

Rationale: The correct answer is A: Intravenous. In cardiovascular collapse, immediate action is crucial. Intravenous administration ensures rapid delivery of medications directly into the bloodstream, achieving quick onset of action. Oral route is too slow, rectal route may be unreliable, and topical route is not suitable for immediate systemic effects. Intravenous route is the most appropriate in this critical situation.

Correct Answer: C

Rationale: The correct answer is C because drugs with a significant first-pass effect are extensively metabolized by the liver upon oral administration, leading to reduced bioavailability and potentially minimal therapeutic effects. This is due to the high enzymatic activity in the liver that rapidly breaks down the drug before it reaches the systemic circulation. Choices A, B, and D are incorrect because drugs with a significant first-pass effect are not limited to oral administration only, do not bypass hepatic circulation, and are not necessarily converted to more active and fat-soluble forms by the liver.

Correct Answer: B

Rationale: The correct answer is B: Biological half-life. The biological half-life of a drug determines the duration of action and how frequently it needs to be administered. Cephalexin has a short half-life of around 1 hour, so it needs to be given every 8 hours to maintain therapeutic levels. Explanation for why the other choices are incorrect: A: Propensity to go to the target receptor - While this is important for drug efficacy, it does not dictate the dosing frequency. C: Pharmacodynamics - While pharmacodynamics refers to how a drug works in the body, it does not directly impact the dosing interval. D: Safety and side effects - While safety and side effects are important considerations, they do not determine the dosing frequency.

Correct Answer: D

Rationale: The correct answer is D because peak levels indicate the highest concentration of the drug in the bloodstream after administration and trough levels indicate the lowest concentration before the next dose. By measuring both, healthcare providers can ensure the drug is within the therapeutic range for efficacy and safety. Choice A is incorrect as a wide therapeutic range does not negate the need for monitoring levels. Choice B is incorrect as the duration of drug administration does not determine the need for level monitoring. Choice C is incorrect as receptor saturation does not directly relate to the need for peak and trough level monitoring.