A summary of the evidence used in this review, which comes mainly from randomized controlled trials, is found in Box 1. 4 However, we will focus on the most well-known and well-studied interaction: that of interference in the activity of the cytochrome P450 3A4 (CYP3A4) enzyme. It was recently found that grapefruit and certain other citrus juices act by an additional mechanism to cause diminished systemic concentration of certain drugs by inhibiting drug transporters. We focus on grapefruit because it is the most widely examined, but other citrus fruits may have similar consequences. This review identifies the key scientific concepts and clinical implications of grapefruit–drug interactions relevant to medical practice. This increase is a result of the introduction of new chemical entities and formulations. Between 20, the number of medications with the potential to interact with grapefruit and cause serious adverse effects (i.e., torsade de pointes, rhabdomyolysis, myelotoxicity, respiratory depression, gastrointestinal bleeding, nephrotoxicity) has increased from 17 to 43, representing an average rate of increase exceeding 6 drugs per year. Recently, however, a disturbing trend has been seen. Many of the drugs that interact with grapefruit are highly prescribed and are essential for the treatment of important or common medical conditions. This interaction enhances systemic drug concentration through impaired drug metabolism. 1 – 3 Currently, more than 85 drugs, most of which are available in Canada, are known or predicted to interact with grapefruit. The content in naringin, the most important flavanone in citrus fruit, varied between 1.98 and 51.2 mg/100 mL juice.Our research group discovered the interaction between grapefruit and certain medications more than 20 years ago. In juice prepared from fruit pulp, the concentrations were 81.92 mg/100 mL, 108.23 mg/100 mL and 65.76 mg/100 mL, respectively. They praised a different content in flavonoidic compounds for citric and for the rest of analyzed fruits.įor grapefruit juices the concentrations in flavonoidic compounds are higher in total fruit juice: 143.86 mg/100 mL in red, 131.47 mg/100 mL in pink and 84.21 mg/100 mL in white grapefruit juice. The experimental researches had as object the comparative study of total content of flavonoidic compounds, like naringin in different fruit juices: citric fruit (white, pink and red grapefruit), apples, pears-industrial or laboratory prepared juices (by squeezing). The most important compounds of GFJ considered to be involved in the pharmacokinetic interaction are flavonoids (naringin, naringenin, narirutin, quercetin, kaempferol, hesperidin, neohesperidin, didymin, and poncirin), furanocoumarins (6',7'-dihydroxy-bergamottin, bergamottin, bergamottin-6',7'-epoxide, bergapten, epoxy-bergamottin) and sesquiterpens (noot-katone). Grapefruit inhibits the cytochrome P450 3A4 enzyme system responsible for the oxidative metabolism of many orally administered drugs. All these drugs are metabolized to a large extent by the most abundant human isoform of cytochrome P450, CYP3A4. Since 1989, grapefruit juice is reported to modify, with clinical implications, the pharmacokinetic of a series of drugs such as calcium channel blockers that are dihydropyridine derivates and/or some HMGCoA reductase inhibitors.
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