Which drug decreases cholesterol synthesis by inhibiting HMG CoA reductase?

Lovastatin is a drug that specifically works by inhibiting HMG CoA reductase, an enzyme that plays a crucial role in the biosynthesis of cholesterol in the liver. By blocking this enzyme, lovastatin effectively reduces the production of cholesterol, which can lead to lower levels of low-density lipoprotein (LDL) cholesterol in the bloodstream. This mechanism is a principal force behind lovastatin and other statins' effectiveness in reducing cardiovascular disease risk by managing cholesterol levels.

The other drugs listed function through different mechanisms. Fenofibrate is a fibrate that primarily reduces triglyceride levels and can increase high-density lipoprotein (HDL) cholesterol, but it does not inhibit HMG CoA reductase. Cholestyramine is a bile acid sequestrant that lowers cholesterol by binding bile acids in the intestine, preventing their reabsorption. Gemfibrozil also belongs to the fibrate class and is used to lower triglycerides but does not directly inhibit the enzyme responsible for cholesterol synthesis. Therefore, lovastatin is uniquely effective in its specific inhibition of HMG CoA reductase, leading to decreased cholesterol synthesis.