Cholesterol drugs fall into four major categories.
They are bile acid binding resins e.g. Cholestyramine, nicotinic acid agents e.g. Niacin, Fibrates e.g. Gemfibozil, cholesterol adsorption inhibitors e.g. Ezetimibe and Statins.
Out of the four, Statin is the more effective than those in the other categories and tend to be much better tolerated. Examples of commercially available Statin drugs in the market are Lovastatin, Pravastatin, Atorvastatin and Simvastatin.
Statin inhibits the liver enzyme HMG-CoA reductase, which significantly reduces the production of cholesterol by the liver. It results in a significant reduction in LDL cholesterol, with a modest decrease in triglycerides, and a modest increase in HDL cholesterol. Statin however can cause elevations in liver enzymes and therefore need to be monitored.
Bile acid binding resins prevent the cholesterol in bile from being reabsorbed in the gut. These resins have significant side effects such as intestinal gas and gallstones, which significantly limit their usefulness. They can also cause a decrease in absorption of other drugs, vitamin deficiencies and occasionally an increase in triglyceride levels.
Niacin is one of the B vitamins. When used in large doses, it can significantly reduce LDL cholesterol and increase HDL cholesterol. They mechanism by which it works in however not very well understood. Niacin is very effective but has significant side effects such as skin flushing, severe itching and gastrointestinal disturbances and poorly tolerated. As such it use is somewhat limited.
Fibrates such as Gemfibozil and Clofibrate help lower triglycerides. They are however less effective with LDL cholesterol. Like bile acid binding resins they have significant side effects such as gastrointestinal disturbances and gallstones.
Cholesterol absorption inhibitors is a new class of drugs. It inhibits the intestinal absorption of cholesterol found in bile and the diet. It can reduce LDL cholesterol by 18-20% and increase HDL cholesterol but does not work on triglycerides. It is generally well tolerated with little or no side effects when taken on its own.