Posted by SalArmy4me on July 31, 2001, at 0:48:47
Journal of Clin. Psychopharmacology, August 2001
Drug Interactions With Grapefruit Juice: An Update.
Greenblatt, David J. MD."Drug interactions with grapefruit juice will occur after a single exposure to a usual dose (such as a single 8-ounce glass). There may be variations in the extent of drug interactions depending on the source and method of preparation of grapefruit juice. Duration of exposure to grapefruit juice also is of importance. There is evidence that CYP3A inhibition may increase with repeated doses of grapefruit juice, 29 although the effect of exposure for longer than 7 to 10 days is largely unknown.
Public Health Implications
As with many issues involving the relation of prescription medications to food products or to herbal medicines, media coverage and reporting has often been excessive and unbalanced. It now is possible to evaluate the problem of grapefruit juice interactions with prescription drugs in the context of a realistic assessment of risk. Although some drugs are affected by an interaction with grapefruit juice, most are not. Individuals taking unaffected drugs may continue to take grapefruit juice with no hazard or problem. In most cases, the medications that are affected have been identified or can be predicted based on their established pathways of metabolism and pharmacokinetic properties. For patients taking medications known to interact with grapefruit juice, there generally are noninteracting alternative medications within each drug class that should allow appropriate treatment to proceed safely with no need to avoid grapefruit juice or any other as-yet-unidentified food or natural product that may interact with CYP3A through similar mechanisms. Nonetheless, it must be recognized that it will never be possible to perform a clinical study to confirm or rule out the possibility of an interaction of grapefruit juice with each and every drug that we would like to know about. Basic and clinical research on the subject will continue, and will address such questions as whether grapefruit juice influences the function of transport proteins (such as P-glycoprotein) that may contribute to determining oral bioavailability of some drugs. Ultimately, the management of actual or potential drug interactions with grapefruit juice (or with any other agent) in clinical practice requires a balance of therapeutic judgment together with a knowledge of the science."
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