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Thursday, August 21, 2014
Pharmacy and Medications
Zocor and grapefruit
Is it safe to eat one grapefruit in the morning and take 20 mg of Zocor at 10:00 PM.
The following is the full text of a question we answered in 2003 regarding Simvastatin and grapefruit juice. The information provided can be applied to eating grapefruit as well as drinking the juice. The effect of a daily grapefruit on simvastatin absorption should be minimal. The timing of the simvastatin dose in relation to eating the grapefruit is not important.
Zocor® is one of a number of drugs that are broken down by an enzyme called CYP 3A4 in the intestines before it reaches the blood stream. Another name for Zocor® is simvastatin. Components of the grapefruit juice block the activity of CYP 3A4 and can result in much higher than intended blood levels of the affected drugs. There is some concern that the resultant high drug levels in the blood could lead to an increased risk of toxic effects. The effect of grapefruit juice on the enzyme is thought to be irreversible. That is, the effect lasts until the body is able to regenerate the enzyme. The process of enzyme regeneration takes several days. During this time, increased blood levels of affected drugs can be expected. How long the effect lasts and also the intensity of the effect is related to some extent by the dose of the grapefruit juice ingested. At grapefruit juice doses in excess of about a quart a day, very large increases in the simvastatin blood levels have been reported. This effect gradually abates over the course of about three days. Smaller doses of grapefruit juice result in smaller increases in peak blood levels, and the effect can be present for at least 24 hours. However, the package insert for Zocor® (simvastatin) indicates that daily ingestion of 8 ounces of regular strength grapefruit juice in the morning followed by simvastatin in the evening produced only minor increases in simvastatin blood levels. The effect of doses of grapefruit juice greater than 8 ounces, but less than 32 ounces (1 quart) has not been studied. There is some evidence that increased levels of simvastatin can increase the risk of developing muscle breakdown and rhabdomyolysis. Whether slightly elevated simvastatin blood levels put patients at higher risk for developing toxic side effects is controversial. An occasional glass of grapefruit juice should not significantly increase the risk of toxicity with simvastatin. Many clinicians feel that normal daily doses of grapefruit juice (about 8 ounces a day) do not increase the risk . Higher doses of grapefruit are more worrisome. Cautions daily ingestion of 8 ounces or less of grapefruit juice in the morning followed by a daily dose of simvastatin in the evening should be relatively safe. Higher doses of grapefruit juice may increase the risk of developing toxicity and should probably be avoided. If you develop muscle tenderness or darkened urine or both while using simvastatin, stop the medicine and contact your physician as soon as possible. Another cholesterol lowering medicine called pravastatin (Pravachol® Bristol Myers Squibb) is not affected by grapefruit juice. Pravastatin may be an alternative to simvastatin in some patients who want to continue to ingest large amounts of grapefruit juice regularly. Two other HMG-CoA reductase inhibitors, rosuvastatin(Crestor® AstraZeneca),and fluvastatin (Lescol® Novartis) are not thought to interact with grapefruit juice. As always, feel free to discuss you these issues with your doctor or a pharmacist who knows you.
Robert James Goetz, PharmD, DABAT
Assistant Professor of Pharmacy Practice
College of Medicine
University of Cincinnati