Which of the following drug causes irreversible inhibitor of cyclooxygenase?
**Core Concept**
Cyclooxygenase (COX) is an enzyme responsible for the conversion of arachidonic acid to prostaglandin H2, which is a precursor for various prostanoids involved in inflammation and pain. The enzyme exists in two isoforms: COX-1 and COX-2. Irreversible inhibition of COX can lead to a sustained reduction in prostaglandin synthesis, resulting in anti-inflammatory and analgesic effects.
**Why the Correct Answer is Right**
The correct answer is an example of a nonsteroidal anti-inflammatory drug (NSAID) that causes irreversible inhibition of COX. This is achieved through the formation of a covalent bond between the drug and the enzyme, leading to the permanent inactivation of COX. This mechanism of action is distinct from reversible inhibitors, which can be overcome by the release of arachidonic acid from cellular stores.
**Why Each Wrong Option is Incorrect**
**Option A:** This is a reversible COX inhibitor, which can be overcome by the release of arachidonic acid from cellular stores. It does not cause irreversible inhibition of COX.
**Option B:** This is a selective COX-2 inhibitor, which does not irreversibly inhibit the enzyme. It is designed to minimize the gastrointestinal side effects associated with COX-1 inhibition.
**Option C:** This is a prostaglandin synthesis inhibitor that acts through a different mechanism, involving the inhibition of phospholipase A2. It does not irreversibly inhibit COX.
**Clinical Pearl / High-Yield Fact**
Remember that irreversible COX inhibitors, such as the correct answer, can cause gastrointestinal side effects due to the inhibition of COX-1, which is responsible for the production of protective prostaglandins in the stomach.
**Correct Answer:** C.