When you take two or more drugs together, there is always the potential for interactions. These are called drug-drug interactions. Sometimes, certain foods or drinks may also affect the way your medicine works. These are known as drug-food interactions. Grapefruit is an example of a food that interacts with a number of drugs, including cholesterol medications.
Types of Cholesterol Medications
To treat high cholesterol, your doctor has a myriad of cholesterol-lowering medications to prescribe. The majority of them fall into one of three major classes, namely the bile acid sequestrants, fibric acid derivatives and the statins. The bile acid sequestrants include cholestyramine, colestipol and colesevelam. Fibric acid derivatives include gemfibrozil and fenofibrate. Examples of statins are atorvastatin, lovastatin and rosuvastatin. Niacin and ezetimibe are two cholesterol-lowering medications that don't fit into the other classes.
Grapefruit Interactions and Cholesterol Medications
Each class of cholesterol medications differs in its interaction profile. The fibric acid derivatives, bile acid sequestrants, ezetimibe and niacin are not affected by grapefruit or grapefruit juice. However, grapefruit juice potentially interacts with the statins, known medically as HMG-CoA reductase inhibitors. However, they interact to different degrees, and some don't interact at all. Atorvastatin--brand name, Lipitor--lovastatin--Mevacor--and simvastatin--Zocor--are affected by grapefruit juice. Other statins, such as rosuvastatin--Crestor--fluvastatin--Lescol--and pravastatin--Pravachol--don't exhibit an interaction with grapefruit juice and may serve as therapeutic alternatives to the others.
Mechanism Of the Interaction
The mechanism by which grapefruit juice exerts its effect is by blocking an enzyme in the walls of the intestine that's responsible for breaking down the statin. Usually, when you take a drug, at some point after administration, your body inactivates it or breaks it down before it's eliminated from your body. This process is called metabolism and primarily takes place in the liver. An enzyme system called cytochrome P450 is responsible for the metabolism of statins. A component of grapefruit juice blocks one of the enzymes of this system. By doing so, it inhibits the metabolism of the statin.
Significance
Blocking the metabolism of the statin results in a larger concentration of the drug in your body. In other words, more of the active drug remains in your system rather than being eliminated. For example, when atorvastatin is mixed with grapefruit juice, the amount of available drug in your blood is increased by 150 percent. This increase leads to possible toxicity and an increased risk of side effects and serious adverse reactions of the muscles, such as muscle pain, weakness and/or damage. The risk for developing a rare condition called rhabdomyoysis, which involves destruction of a muscle, also increases when too much grapefruit juice is mixed with a statin.
Preventions/Warnings
You can minimize or prevent the effects of grapefruit juice by limiting your daily intake to 32 ounces or less. If you would rather not concern yourself with such restrictions, let your doctor know. He or she can switch you to a statin that has less or no potential for interaction with grapefruit juice or to another class of cholesterol-lowering medication.
