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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]
Some substances, such as some drugs and furanocoumarins present in grapefruit juice, interfere with the action of CYP3A4. These substances will, therefore, either amplify or weaken the action of those drugs that are modified by CYP3A4. CYP3A4 is a member of the cytochrome P450 family of oxidizing enzymes. Several other members of this family ...
Grapefruit juice is a CYP3A4 inhibitor and should be avoided when taking pazopanib. It is also a weak inhibitor of other liver enzymes, CYP2C8 and CYP2D6. [8] Axitinib is metabolized by CYP3A4 and UGT1A1. Strong inhibitors of CYP3A4 will increase the plasma concentration of axitinib, while weak inhibitors have less effect on the plasma ...
For example, when the blood pressure drug felodipine is taken with grapefruit juice rather than water, levels of the medication in the blood can more than double and result in headache, irregular ...
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]
Enzyme induction (increased rate of metabolism), e.g., Phenytoin induces CYP1A2, CYP2C9, CYP2C19, and CYP3A4; Enzyme inhibition (decreased rate of metabolism), e.g., grapefruit juice inhibits CYP3A → higher nifedipine concentrations; Individual variation in metabolic differences
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]
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 ...