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The effects last because grapefruit-mediated inhibition of drug metabolizing enzymes, like CYP3A4, is irreversible; [30] that is, once the grapefruit has "broken" the enzyme, the intestinal cells must produce more of the enzyme to restore their capacity to metabolize drugs that the enzyme is used to metabolize. [19]
Cytochrome P450 3A4 (abbreviated CYP3A4) (EC 1.14.13.97) is an important enzyme in the body, mainly found in the liver and in the intestine, which in humans is encoded by CYP3A4 gene. It oxidizes small foreign organic molecules ( xenobiotics ), such as toxins or drugs, so that they can be removed from the body.
Grapefruit and grapefruit juice have been found to interact with numerous drugs, in many cases resulting in adverse effects. [4] This happens in two ways: one is that grapefruit can block an enzyme which metabolizes medication, [5] and if the drug is not metabolized, then the level of the drug in the blood can become too high, leading to an adverse effect. [5]
Grapefruit–drug interactions are common, as the juice contains furanocoumarins that interfere with the metabolism of many drugs. This can prolong and intensify the effects of those drugs, leading to multiple side-effects such as abnormal heart rhythms, bleeding inside the stomach, low blood pressure, difficulty breathing, and dizziness.
Grapefruit juice can act as an enzyme inhibitor, affecting the metabolism of drugs. In pharmaceutical sciences , drug interactions occur when a drug's mechanism of action is affected by the concomitant administration of substances such as foods, beverages, or other drugs.
Because of this risk, avoiding grapefruit juice and fresh grapefruits entirely while on drugs is usually advised. [13] Other examples: Saint-John's wort, a common herbal remedy induces CYP3A4, but also inhibits CYP1A1, CYP1B1. [14] [15] Tobacco smoking induces CYP1A2 (example CYP1A2 substrates are clozapine, olanzapine, and fluvoxamine) [16]
This prevents oxidative metabolism of certain drugs by the enzyme, resulting in an elevated concentration of drug in the bloodstream. Under normal circumstances, the grapefruit juice effect is considered to be a negative interaction, and patients are often warned not to consume grapefruit or its juice when taking medication.
Furanocoumarins in grapefruit juice (i.e. bergamottin and dihydroxybergamottin) inhibit the cytochrome P450 enzyme CYP3A4, which is involved in the metabolism of most statins (however, it is a major inhibitor of only lovastatin, simvastatin, and to a lesser degree, atorvastatin) and some other medications [129] (flavonoids (i.e. naringin) were ...