Like you, I love the taste of grapefruit. And it contains many healthy nutrients. However, one of those nutrients called furanocoumarins can raise the blood levels of certain medications, including atorvastatin.

Furanocoumarins block an enzyme called CYP3A4 in the intestine. This enzyme metabolizes (breaks down) many different drugs. Some drugs are broken down only a little by CYP3A4. For other drugs, CYP3A4 is the most important metabolic enzyme. Atorvastatin is one of those drugs.

Drug makers estimate how much effect the CYP3A4 enzyme will have on each drug. This helps determine the proper dose.

CYP3A4 has a large effect on the breakdown of atorvastatin. When eating grapefruit or drinking its juice, you block the enzyme. So, you end up having a lot more atorvastatin go into your blood. This could cause major side effects.

The side effect doctors worry about the most with all statins is muscle damage. Extensive muscle damage releases chemicals into the blood that can cause kidney failure.

The interaction between atorvastatin and grapefruit depends on the dose of the drug, the amount of fruit and juice you take in. If you take a low dose atorvastatin and occasionally had a little fruit or juice, it’s likely okay. But it is still best to avoid grapefruit completely.

Most other statins also are broken down by the CYP3A4 enzyme. People that take either lovastatin and simvastatin should also avoid grapefruit and its juice. Pravastatin (Pravachol) is one statin that does not interact with grapefruit.