Grapefruit interferes with an enzyme called cytochrome P450 (there are many), however, only a few are relevant for drug metabolism. Grapefruit interferes with P450 3A4 which is one of the most popular enzymes to metabolize drugs, therefore there is a lot of drug interactions. Since the grapefruit competes with these drugs to be broken down by the enzyme it takes longer for the drug to be metabolized than normal. Therefore the active drug will remain in your body longer than normal since it is getting broken down slower. This can lead to toxic levels of the drug, some drugs more serious than others. This particular "statin" drug, rosuvastatin or
Crestor, is not metabolized by P 450 3A4 and therefore is not a drug interaction even though most in the
drug class are an interaction. If I was at work and someone got their drugs quickly I would probably say not to drink grapefruit because you can't remember weird exceptions like crestor when essentially all the other ones interact with it. Hope this maybe gives slightly better and hopefully not too confusing of an explanation, haha. Cheers!
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---I answer questions to the best of my ability, but with always limited knowledge of the patient's situation and obviously I can not see your chart or full medical history my advice is limited and should also be confirmed with your own doctor/pharmacist/etc. and I do not promote following my advice without proper approval from your doctor either--
Dr. B