Which drug class lowers cholesterol by inhibiting the rate-limiting enzyme in cholesterol synthesis?

• A. Bile acid sequestrants
• B. Statins
• C. Niacin
• D. Fibric acids

Answer: (B)

Inhibiting the rate-limiting step of cholesterol synthesis is achieved by statins. They block HMG-CoA reductase, the enzyme that converts HMG-CoA to mevalonate in the cholesterol biosynthesis pathway. This lowers hepatic cholesterol production, which then upregulates LDL receptors on liver cells, increasing clearance of LDL from the blood and thereby lowering LDL cholesterol levels. The other drug classes modify cholesterol through different mechanisms—bile acid sequestrants bind bile acids in the gut, niacin reduces VLDL production and raises HDL, and fibric acids activate PPAR-alpha to alter lipoprotein metabolism—so they do not inhibit the rate-limiting enzyme in cholesterol synthesis.