Grapefruit juice is a potent inhibitor of the cytochrome P450 CYP3A4 enzyme, which can impact the metabolism of a variety of drugs, increasing their bioavailability.

Grapefruit juice can enhance efficacy of some statins reducing low density lipoprotein cholesterol and heart disease.

Interacts with as many as 85 drugs.

Grapefruit juice reduces intestinal P450 3A4.

Can lead to a fatal interaction with drugs like astemizole or terfenadine.

Drugs that may be affected include alprazolam, caffeine, cyclosporine, dextromethorphan, diazepam, felodipine, ketamine, lorazepam, lovastatin, methadone, midazolam, oxycodone, simvastatin, pravastatin, sildenafil, as well as a number of antihistamines including astemizole and terfenadine.

Can increase both the bioavailability of some benzodiazepines, and greatly slow the rate of metabolisation.

Other known CYP3A4 inhibitors include erythromycin, itraconazole, and ketoconazole.

Affects the metabolism of many medications, increasing the risk of toxicity and adverse events.

Inhibits the activity of CYP3A4 in the intestines and presumably inhibits degradation of statins and so increases their systemic bioavailability.

Characteristics of oral medications that may interact with grapefruit include extensive metabolism through the intestinal cytochrome P450 3A4 (CYP3A4) system, low bioavailability, and a narrow therapeutic index.

Grapefruit juice interacts through the intestinal CYP3A4 system and can inhibit the concentration for 24–72 hours.

Caution should be taken and adverse reactions when taking medications that may interact with grapefruit or juice.

Increases the risk of colchicine-induced toxic effects; significant increase in colchicine plasma concentration occurs.

Inhibits CYP3A4-mediated metabolism of oral amiodarone resulting in increase plasma levels.

As a moderate inhibitor of CYP3A, resulting in a 3-fold increase in dronedarone exposure.

Could increase systemic dofetilide exposure.

Associated with a 1.6-fold increase in the Cmax and a 1.9-fold increase in the AUC of praziquantel.

Avoid co-administration with antipsychotic agent pimozide.

Associated with a 2-fold increase in felodipine, and nifedipine AUC and Cmax.

3-fold increase in nisoldipine Cmax and 2-fold increase in nisoldipine AUC. Avoid co-administration before and after dosing.

May significantly increase concentrations of verapamil.

Large quantities can increase plasma concentrations of atorvastatin, lovastatin, and simvastatin.

Cytochrome P450 (CYP3A4) is the major enzyme in the metabolic degradation of many statins including atorvastatin, simvastatin, and lovastatin.

The main agent responsible for the grapefruit juice effect on statins are bergamottin in fresh grapefruit and its derivative 6’7′ dihydroxybergamottin in juice concentrate, which are furanocoumarins.

Bergamottin and its derivative inactivate CYP3A4.

May increase exposure of ivacaftor.

Potential risk for serious toxicity exists with ergotamine tartrate plus caffeine.

May reduce bioavailability of fexofenadine.

Results in a 1.8-fold increase in exposure to tolvaptan.

Increases concentrations of cyclosporine, tacrolimus, temsirolimus, and everolimus.

Increases cilostazol by about 50%.

Concurrent Ruxolitinib can enhance thrombocytopenia.

May increase exposure of everolimus, axitinib, and ixabepilone, dasatinib, sunitinib, nilotinib, lapatinib, pazopanib, and crizotinib.

May dangerously increase fentanyl plasma concentrations.

Increases tadalafil, vardenafil levels.

Markedly increases buspirone, and triazolam doses.

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