The antiplatelet drug clopidogrel has to be activated by enzymes to bring about its effect.Antibiotics like erythromycin which help fight against certain bacterial infections are made more potent and can cause side effects when taken with grapefruit.Other Important Drug Interactions with Grapefruit: Cyclosporin when given with grapefruit juice may increase the damage caused to the kidneys and bone marrow due to higher blood levels. Immunosuppressants are drugs which inhibit immune response in the body and are used in the treatment of autoimmune disorders and during transplantation of organs. Cardiovascular Drugs/Anti-arrhythmic Drugs.The possible drug interactions with grapefruit which could be harmful are as follows: What Are The Possible Drug Interactions With Grapefruit?įood-drug interaction is an interaction of a drug with some food when taken together. This increased serum drug level is the cause for severe adverse effects. As a consequence, the blood levels of the drugs metabolized by the enzyme increase. These active ingredients of fresh grapefruit and grapefruit juice interact with and inhibit the CYP3A4 enzyme, which inactivates or metabolizes several drugs in the intestinal lining and the liver. Furanocoumarins like bergamottin and dihydroxybergamottin are also present in the fruit. Grapefruit contains large amounts of the flavanoid naringin. Although in vitro findings support the flavonoid, naringin, or the furanocoumarin, 6',7'-dihydroxybergamottin, as being active ingredients, a recent investigation indicated that neither of these substances made a major contribution to grapefruit juice-drug interactions in humans.How Does The Grapefruit-Drug Interaction Occur? The importance of the interaction appears to be influenced by individual patient susceptibility, type and amount of grapefruit juice and administration-related factors. Clinically relevant interactions seem likely for most dihydropyridines, terfenadine, saquinavir, cyclosporin, midazolam, triazolam and verapamil and may also occur with lovastatin, cisapride and astemizole. Medications with innately low oral bioavailability because of substantial presystemic metabolism mediated by CYP3A4 appear affected by grapefruit juice. At least 20 other drugs have been assessed for an interaction with grapefruit juice. The high variability of the magnitude of effect among individuals appeared dependent upon inherent differences in enteric CYP3A4 protein expression such that individuals with highest baseline CYP3A4 had the highest proportional increase. Since the duration of effect of grapefruit juice can last 24 h, repeated juice consumption can result in a cumulative increase in felodipine AUC and Cmax. Subsequent investigations showed that grapefruit juice acted by reducing presystemic felodipine metabolism through selective post-translational down regulation of cytochrome P450 3A4 (CYP3A4) expression in the intestinal wall. The novel finding that grapefruit juice can markedly augment oral drug bioavailability was based on an unexpected observation from an interaction study between the dihydropyridine calcium channel antagonist, felodipine, and ethanol in which grapefruit juice was used to mask the taste of the ethanol.
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