**Question:** Antihypeensive drug that causes Coombs test positive is

A. Aspirin
B. Enalapril
C. Captopril
D. Captopril

**Core Concept:**

Coombs test is a blood test that detects antibodies against red blood cells, which can indicate hemolysis (destruction of red blood cells) or hemolysis-related disorders. The test can be falsely positive due to medications that bind to red blood cells and mimic hemolysis.

**Why the Correct Answer is Right:**

Drugs like captopril (an angiotensin-converting enzyme inhibitor) can lead to Coombs test positivity due to their interaction with red blood cells. Captopril binds to the surface of red blood cells, causing them to agglutinate (clump together) and leading to a positive Coombs test result.

**Why Each Wrong Option is Incorrect:**

A) Aspirin (salicylic acid) is a non-selective COX inhibitor that primarily targets the platelet cyclooxygenase enzyme, not red blood cells. Aspirin does not cause a positive Coombs test.

B) Enalapril is an angiotensin-converting enzyme inhibitor like captopril, but it does not cause a positive Coombs test. The mechanism behind captopril causing the test to be positive is unique to its binding to red blood cells.

C) Captopril is the correct answer, so this option is incorrect as it is identical to the correct answer.

**Clinical Pearl:**

In clinical practice, understanding the mechanism behind medications affecting the Coombs test can help differentiate between false-positive results due to medications and true hemolysis or hemolysis-related disorders. This knowledge is crucial in interpreting test results accurately and making appropriate diagnostic and therapeutic decisions.