There are currently five statin drugs on the market in the United States: lovastatin, simvastatin, pravastatin, fluvastatin, and atorvastatin. The major effect of the statins is to lower LDL-cholesterol levels, and they lower LDL-cholesterol more than other types of drugs. Statins inhibit an enzyme, HMG- CoA reductase that controls the rate of cholesterol production in the body. This drug lowers cholesterol by slowing down the production of cholesterol and by increasing the liver's ability to remove the LDL-cholesterol already in the blood. The large reductions in total and LDL-cholesterol produced by these drugs resulted in large reductions in heart attacks and heart disease deaths. Thanks to their track record in these studies and their ability to lower LDL-cholesterol, statins have become the drugs most often prescribed when a person with heart disease needs a cholesterol- lowering medicine.
Studies using statins have reported 20 to 60 percent lower LDL-cholesterol levels in patients on these drugs. Statins also reduce elevated triglyceride levels and produce a modest increase in HDL-cholesterol.
The statins are usually given in a single dose at the evening meal or at bedtime. It is important that these medications be given in the evening to take advantage of the fact that the body makes more cholesterol at night than during the day.
You should begin to see results from the statins after several weeks, with a maximum effect in 4 to 6 weeks. After about 6 to 8 weeks, your doctor can do the first check of your LDL-cholesterol while on the medication. A second measurement of your LDL-cholesterol level will have to be averaged with the first for your doctor to decide whether your dose of medicine should be changed to help you meet your goal.
This answer is based on source information from National Heart, Lung and Blood Institute.