More than 90% of this drug is excreted in the urine in intact form. Because its urinary solubility is low, patients should be well hydrated to prevent nephrotoxicity. The drug is:

**Core Concept**
The question is testing the student's knowledge of **pharmacokinetics**, specifically the **renal excretion** of drugs and the importance of **urinary solubility** in preventing **nephrotoxicity**.

**Why the Correct Answer is Right**
The correct answer is a drug that is primarily excreted unchanged in the urine, with low urinary solubility. This requires patients to be well hydrated to prevent **crystalluria** and subsequent **nephrotoxicity**.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because the question is about a specific drug that is excreted in the urine in intact form, and Option A does not match this description.
**Option B:** This choice is also incorrect as it does not have the characteristics mentioned in the question.
**Option C:** This option is incorrect for similar reasons as Options A and B.

**Clinical Pearl / High-Yield Fact**
It is crucial to remember that drugs with low urinary solubility, such as **methotrexate**, require adequate hydration to prevent **kidney damage**.

**Correct Answer:** D. Methotrexate

✓ Correct Answer: C. Acyclovir