Which of the following is a cholesterol absorption inhibitor?

Ezetimibe is classified as a cholesterol absorption inhibitor because it specifically works by decreasing the intestinal absorption of cholesterol. It functions by targeting a protein in the intestinal brush border, inhibiting the uptake of dietary cholesterol and cholesterol secreted in bile. This leads to a reduction in the plasma cholesterol levels, making it particularly effective as part of a lipid-lowering strategy, often in combination with statins for a more potent effect.

In contrast, gemfibrozil primarily reduces triglyceride levels and raises HDL cholesterol and is classified as a fibric acid derivative. Atorvastatin is a statin that works by inhibiting HMG-CoA reductase, an enzyme crucial for cholesterol synthesis in the liver, rather than affecting its absorption. Fentanyl, on the other hand, is an opioid analgesic and is unrelated to cholesterol metabolism or absorption. Understanding these distinctions clarifies why ezetimibe is identified specifically for its unique mechanism of inhibiting cholesterol absorption.