Final answer:
Cholestyramine, colestipol, and colesevelam are bile acid sequestrants that lower blood cholesterol levels by binding to bile acids in the intestine, preventing their reabsorption and leading to increased conversion of cholesterol into bile acids in the liver.
Step-by-step explanation:
The mechanism of action (MOA) of bile acid sequestrants, which include cholestyramine, colestipol, and colesevelam, involves binding to bile acids in the gastrointestinal tract. These medications bind to bile acids which are derived from cholesterol and form a complex that is too large to be absorbed by the intestines. As a result of this binding, the bile acid-drug complexes are excreted in the feces rather than being reabsorbed. This loss of bile acids prompts the liver to convert more cholesterol into bile acids, thereby lowering the level of cholesterol in the blood.
Additionally, because bile acids play a role in the emulsification and absorption of fats, the disruption of bile acid recirculation can reduce the absorption of dietary fats and cholesterol. These effects lead to a decrease in low-density lipoprotein (LDL) cholesterol levels in the blood, which is beneficial for patients with hyperlipidemia.
Unlike some other cholesterol-lowering drugs, such as statins, which inhibit the enzyme HMG-CoA reductase to reduce cholesterol synthesis, bile acid sequestrants work within the digestive system to prevent the reabsorption of bile acids, indirectly reducing overall cholesterol levels.