TRUE statement about aspirin is :
**Core Concept**
Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that acts by inhibiting cyclooxygenase (COX) enzymes, leading to reduced production of prostaglandins and thromboxanes. This action is responsible for its analgesic, anti-inflammatory, and antiplatelet effects.
**Why the Correct Answer is Right**
Aspirin selectively inhibits COX-1 and COX-2 enzymes, with a particular effect on COX-1, which is responsible for the production of thromboxane A2 in platelets. This leads to a decrease in platelet aggregation, making aspirin an effective antiplatelet agent. Additionally, aspirin's ability to inhibit COX-2 is responsible for its anti-inflammatory effects.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while aspirin does have analgesic and anti-inflammatory effects, it is not the primary mechanism of action responsible for its antiplatelet effects.
**Option B:** This option is incorrect because the irreversible inhibition of COX enzymes by aspirin is a key feature of its pharmacology, but it is not the only mechanism by which aspirin exerts its effects.
**Option C:** This option is incorrect because while aspirin does have a role in reducing inflammation, its primary mechanism of action is not through the inhibition of lipoxygenase enzymes.
**Clinical Pearl / High-Yield Fact**
Aspirin's antiplatelet effects are irreversible due to its ability to acetylate and permanently inhibit COX enzymes, making it a long-lasting antiplatelet agent.
**Correct Answer: D. Aspirin exerts its antiplatelet effect by selectively inhibiting COX-1 enzyme in platelets.**