Different classes of cholesterol-lowering medications work by different mechanisms. Statins block cholesterol synthesis in the liver, while cholesterol absorption inhibitors decrease cholesterol absorption. Other drugs increase bile production; since bile removes cholesterol, more cholesterol is removed from the body when bile production increases. Some cholesterol-lowering medications and anticoagulants or blood-thinning drugs may interact, increasing the risk of complications. Ask your medical practitioner before taking blood thinners or anticoagulants and cholesterol medications together.
When statins interact with many medications, the end result is higher than normal statin levels in the blood. With anticoagulants such as warfarin, however, the opposite occurs. Some types of statins, but not all, interfere with the breakdown of warfarin, so more warfarin stays in the bloodstream. Higher levels of warfarin result in a potential increased risk of bleeding. Other cholesterol-lowering medications such as niacin can have the same effect on warfarin.
Not all anticoagulants interact with all cholesterol-lowering medications. A study published in the July 24, 2007 issue of the "Journal of the American College of Cardiology" by researchers from the University of Kentucky examined the risk of increased complications in patients taking statins in addition to clopidogrel, sold commercially as Plavix, an anti-clotting medication. No increase in cardiovascular complications was found in patients taking both. Different statins also have different effects. While most statins interfere with warfarin and increase bleeding time, pravastatin has no effect on bleeding times.
When increased amounts of warfarin accumulate in the blood, the risk of side effects increases. Side effects of warfarin include increased risk of hemorrhagic stroke, internal bleeding or bleeding from injuries. Life-threatening spontaneous bleeding unrelated to any injury can occur. The effects of warfarin last for two to five days after your last dose. Report increased bruising or small pinpoint red spot under the skin, black, tarry stools, vomiting blood or heavy bleeding with menstrual periods for women to your medical practitioner.
Because high cholesterol and increased clotting are both part of the risk for heart attack, many people take both blood thinners and cholesterol-lowering medications. Statin drugs affect anticoagulants to different degrees and also vary from person to person. Close monitoring of bleeding times through frequent blood tests when taking both types of drugs helps avoid serious complications.