Cholesterol drugs are effective in lowering high levels of total cholesterol, LDL cholesterol and triglycerides, which are the fat molecules in the body. The cholesterol-lowering medications include niacin, the bile acid sequestrants, fibrates, HMG-CoA reductase inhibitors, cholesterol absorption inhibitors and omega-3-fatty acids. Grapefruit can interact with HMG-CoA reductase inhibitors, commonly known as statins.
Statins
Statins are the preferred medical therapy in patients who have high cholesterol because they are the most potent in lowering LDL cholesterol, which is the bad cholesterol. Statins work by blocking the HMG-CoA reductase, which is an enzyme involved in the formation of cholesterol. The statins available in the United States, as of February 2011, include simvastatin, atorvastatin, lovastatin, rosuvastatin, pravastatin, fluvastatin and pitavastatin. Simvastatin is also available in combination with niacin and in combination with ezetimibe, which is only cholesterol absorption inhibitor available in the United States. These combination drugs demonstrate similar actions, breakdown and side effects.
Metabolism of Statins
The metabolism, or breakdown, of statins occurs in the liver by cytochrome P450 enzymes. The primary enzyme involved in statin metabolism is the cytochrome P450 3A4 enzyme, or CYP 3A4, states the "Drug Information Handbook." The drug is broken down into simpler parts which can then be easily eliminated from the body. Medications, herbal supplements or foods that affect the CYP 3A4 enzyme can change the levels of statins.
Grapefruit Juice and Statins
Grapefruit juice contains chemicals called furancoumarins, including quercetin, naringin and bergamottin. According to "Pharmacotherapy: A Pathophysiologic Approach," these chemicals are potent inhibitors of CYP 3A4 enzyme, meaning they block the actions of the enzyme. The result is an increase in the level of statins because your body is unable to eliminate them; this can lead to toxic levels, which in turn can increase the risk of myopathy and rhabdomyolysis. Myopathy affects muscle fibers and leads to improper function, while rhabdomyolysis is muscle fiber breakdown. In rhabdomyolysis, the muscle fiber contents go into the blood and enter the kidney, where they can cause damage to the kidney and eventually cause kidney failure.
Prevention
You can prevent side effects by avoiding grapefruit juice while taking statins. If you are on cholesterol-lowering medications and are unsure if any of them contains a statin, check with your physician or pharmacist. Always read the labels on all food and herbal supplements to make sure they do not contain grapefruit juice. Rhabdomyolysis and myopathy are serious adverse reactions that can present as muscle pain, general weakness, stiffness and fatigue; seek medical attention if you develop these symptoms to avoid kidney dysfunction.
References
- "Drug Information Handbook"; Charles F. Lacy, et al.; 2009
- "Pharmacotherapy: A Pathophysilogic Approach"; Joseph T. DiPiro, et al.; 2008
- MayoClinic.com: High Cholesterol
