![]() Some of the most commonly prescribed drugs in 2011-the statins atorvastatin and simvastatin-are identified by the review as having a high (atorvastatin) or very high (simvastatin) risk of interaction with grapefruit. Serious adverse events that have been reported due to grapefruit-drug interactions include heart rhythm problems, heart blockage, muscle deterioration, kidney failure, and blood clots. Elderly patients are most vulnerable because they are less able to compensate for high systemic drug concentrations and because pronounced pharmacokinetic interaction has been found in those 70 years of age and older. Patients aged 45 years and older are at increased risk of grapefruit-drug interactions due to their increased consumption of grapefruit and prescription medications. Medications are at risk of being made more potent in interaction with grapefruit if they are taken orally, have very low to intermediate intrinsic oral bioavailability, and are metabolized by CYP3A4. Different individuals who took felodipine with a 250-ml serving of grapefruit juice had systemic concentrations ranging from 0 to 8 times that observed with water. However, the effect can vary greatly from patient to patient. Repeated intake led to even larger effects drinking 250 ml of grapefruit juice 3 times per day for 6 days led to a systemic drug concentration 5 times that seen with water. For example, a single serving of grapefruit juice (200-250 ml) or a whole grapefruit combined with the antihypertensive felodipine has been shown to yield a systemic drug concentration 3 times that seen with equivalent water intake. Furanocoumarin chemicals are also found in Seville oranges (used to make marmalade), limes, and pomelos, but not in sweet oranges such as navels and Valencias.Įven a relatively small amount of grapefruit can have a large effect on drug concentration levels. However, the grapefruit chemicals impair the action of CYP3A4, allowing the bioactivity of some medications to reach much higher levels than normal, potentially producing adverse effects. These chemicals interact with the cytochrome P450 3A4 (CYP3A4) enzyme, found in the small intestine and liver, which partially inactivates many medications under normal circumstances. At least 85 oral medications can have such interactions with grapefruit, 43 of which can lead to serious side effects, and many of these have been introduced just in the last few years.Ĭompounds in grapefruit called furanocoumarin chemicals are the cause of the increased medication potency. Grapefruit can interact with a broad range of oral medications to significantly increase their effects, according to a review of previous studies published online on November 26, 2012, by the Canadian Medical Association Journal. Compounds in grapefruit can interact with a growing number of oral medications to produce serious side effects, according to a review of previous studies.
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