Hypolipidemic therapy and cholesterol absorption

The advent of safe and effective hypolipidemic therapy has revolutionized the ability of the clinician to optimize abnormalities in the lipid profile. The advent of statin therapy has provided a potent option to decrease low-density lipoprotein and frequently allows achievement of National Cholesterol Education Program target lipid levels with monotherapy. However, lipid goals are frequently not achieved due to inadequate response to therapy or side effects. The role of combination therapy in the optimization of the lipid profile provides a means by which the implementation of pharmacologic agents with synergistic mechanisms of action allows further improvement in circulating levels of low-density lipoprotein cholesterol. Statins have been combined with bile acid resins, fibric acid derivatives, and nicotinic acid. However, bile acid resins, although not systemically absorbed, have significant problems with patient compliance and drug interactions. The implementation of therapy with fibric acid derivatives or nicotinic acid increases the risk of significant side effects such as rhabdomyolysis or liver toxicity. Ezetimibe is a prototype of a new class of agents that specifically block the absorption of cholesterol from the gastrointestinal tract. Ezetimibe has minimal systemic absorption and a metabolic pathway involving enterohepatic circulation that allows for once a day administration due to a prolonged half-life. Ezetimibe lacks the drug interactions that are common with the bile acid resins and it may be utilized as either monotherapy or in combination with other pharmacologic agents. Ezetimibe has a relatively flat dose-response curve and titration is not required. This review centers on the role of pharmacologic agents that act predominantly by the reduction of cholesterol absorption, including colesevelam and ezetimibe.