Pravastatin decreases the production of LDL cholesterol by blocking the action of the enzyme in the liver that is responsible for its production. This decreases the amount of cholesterol in the liver cells, causing them to take up LDL cholesterol from the blood. The decreased cholesterol production and increased removal of LDL cholesterol from the blood ultimately results in lowered blood cholesterol levels.
Pravastatin also causes a small decrease in the production of other 'bad fats' in the blood called triglycerides, and a small increase in the level of HDL cholesterol. This results in lowered levels of 'bad fats' and raised levels of 'good fats' in the blood.