Which of the following drug inhibits aggregation of platelets: September 2005
**Core Concept**
Platelet aggregation is a critical step in the formation of thrombi, leading to various cardiovascular diseases. Inhibitors of platelet aggregation are used to prevent and treat thrombotic disorders. These drugs work by targeting specific receptors or pathways involved in platelet activation and aggregation.
**Why the Correct Answer is Right**
Aspirin (acetylsalicylic acid) is a non-selective COX inhibitor that irreversibly inhibits the enzyme cyclooxygenase (COX), which is essential for the production of thromboxane A2 (TXA2). TXA2 is a potent stimulator of platelet aggregation, and its inhibition prevents platelets from aggregating and forming a blood clot. Aspirin's mechanism of action is due to its ability to acetylate a serine residue in the active site of COX, resulting in the irreversible inhibition of the enzyme.
**Why Each Wrong Option is Incorrect**
**Option A:** Prazosin is an alpha-1 adrenergic receptor antagonist used primarily in the treatment of hypertension and benign prostatic hyperplasia. It does not have a significant effect on platelet aggregation.
**Option B:** Furosemide is a loop diuretic used to treat edema and hypertension. It works by inhibiting the sodium-potassium-chloride cotransporter in the thick ascending limb of the loop of Henle, and it does not affect platelet aggregation.
**Option C:** Metformin is an oral antidiabetic drug used in the treatment of type 2 diabetes mellitus. It works by decreasing hepatic glucose production and increasing insulin sensitivity, and it does not have a direct effect on platelet aggregation.
**Clinical Pearl / High-Yield Fact**
Aspirin's antiplatelet effect is a result of its irreversible inhibition of COX, which lasts for the lifespan of the platelet (approximately 8-12 days). This makes aspirin a useful drug for long-term prevention of cardiovascular events.
**Correct Answer:** A. Aspirin