What type of drug is identified as causing irreversible inhibition of COX-1?

• A. Celecoxib
• B. Aspirin
• C. Ibuprofen
• D. Naproxen

Answer: (B)

The correct choice among the options provided is aspirin because it is a nonsteroidal anti-inflammatory drug (NSAID) that irreversibly inhibits the cyclooxygenase enzyme (COX), specifically COX-1. This irreversible inhibition refers to aspirin's unique mechanism of action, where it acetylates a serine residue in the active site of the COX-1 enzyme, leading to a permanent loss of its activity. This effect results in a long-lasting decrease in the production of thromboxane A2, which is important for platelet aggregation and vascular function.

In contrast, the other medications listed, such as celecoxib, ibuprofen, and naproxen, provide reversible inhibition of the COX enzymes. They bind non-covalently to the COX enzymes, which allows for normal function to return once the drug is cleared from the body. This distinction is crucial for understanding the pharmacodynamics of these drugs, particularly in their use for analgesic and anti-inflammatory effects. The irreversible nature of aspirin's action contributes to its unique role in preventing thromboembolic events, highlighting the importance of its correct identification among conventional NSAIDs.