grapefruit
18 interactions related to grapefruit
grapefruit + red yeast rice
Grapefruit inhibits intestinal CYP3A4, the enzyme that clears red yeast rice's active constituent monacolin K (the same molecule as the statin lovastatin). Blocking this enzyme lets more monacolin K reach the bloodstream, raising its cholesterol-enzyme-blocking activity and the associated risk of muscle-related side effects. This is a food-drug interaction driven by the grapefruit inhibitor, and because some unregulated red yeast rice products carry near-prescription statin content, the risk can be meaningful.
pravastatin + grapefruit
Unlike simvastatin, lovastatin, and atorvastatin, pravastatin is not significantly broken down by the gut enzyme CYP3A4 that grapefruit blocks. Controlled pharmacokinetic studies show grapefruit juice does not meaningfully change pravastatin levels, so grapefruit in normal dietary amounts is fine with this statin.
lovastatin + grapefruit
Grapefruit blocks the intestinal enzyme CYP3A4 that normally limits how much lovastatin reaches your bloodstream. With that enzyme suppressed, lovastatin levels can rise sharply, raising the risk of muscle injury and, rarely, rhabdomyolysis. Spacing the timing does not help because the effect lasts for days.
grapefruit + sildenafil
Sildenafil is broken down mainly by the gut and liver enzyme CYP3A4. Grapefruit juice contains furanocoumarins that block intestinal CYP3A4, modestly raising sildenafil exposure and delaying its peak. This can amplify the headache, flushing, dizziness, and transient blood-pressure drop that are typical of PDE5 inhibitors.
tacrolimus + grapefruit
Grapefruit furanocoumarins irreversibly inhibit intestinal CYP3A4, the enzyme that limits how much tacrolimus reaches the bloodstream. This can raise tacrolimus blood levels enough to cause kidney and nervous-system toxicity. Because the enzyme inhibition lasts for days, separating dose timing does not prevent it.
itraconazole + grapefruit
Grapefruit juice can reduce the absorption of itraconazole capsules in healthy-volunteer studies, lowering antifungal blood levels. The likely mechanism is a rise in gastric pH that interferes with the capsule's dissolution, which outweighs grapefruit's usual CYP3A4-inhibiting effect.
fluconazole + grapefruit
Fluconazole is a moderate inhibitor of the liver enzyme CYP3A4, and grapefruit irreversibly inhibits intestinal CYP3A4. Their effects overlap on the same enzyme. On their own the pair rarely causes a problem, but together they can further slow the clearance of a third medication that also depends on CYP3A4, allowing its blood levels to rise.
amlodipine + grapefruit
Amlodipine is a CYP3A4 substrate, but unlike other dihydropyridine calcium channel blockers such as felodipine and nisoldipine, its high oral bioavailability and slow elimination mean grapefruit juice does not meaningfully alter its pharmacokinetics in controlled trials. Some product labels and consumer references still list a theoretical interaction, but the clinical signal at ordinary dietary intakes is small to negligible.
diltiazem + grapefruit
Grapefruit inhibits intestinal CYP3A4, modestly and unpredictably increasing systemic exposure to diltiazem.
grapefruit + carbamazepine
Grapefruit juice inhibits the intestinal CYP3A4 enzyme that performs first-pass metabolism of carbamazepine, allowing more of each oral dose to reach the bloodstream. A human study in epilepsy patients found grapefruit juice raised carbamazepine blood levels, which matters because carbamazepine has a narrow safety margin.
grapefruit + methadone
Grapefruit inhibits intestinal CYP3A4, an enzyme that partly clears methadone, which can raise methadone blood levels. The effect is usually modest in stable patients but can become clinically significant with sustained heavy intake.
grapefruit + oxycodone
Oxycodone is broken down mainly by the intestinal enzyme CYP3A4. Grapefruit juice blocks that enzyme, so more active oxycodone reaches the bloodstream and stays there longer, and metabolism shifts toward the more potent metabolite oxymorphone. A controlled study in healthy volunteers confirmed grapefruit juice meaningfully raises oxycodone exposure, increasing the risk of excessive sedation and slowed breathing.
amiodarone + grapefruit
Grapefruit and grapefruit juice inhibit intestinal CYP3A4, the enzyme that metabolizes oral amiodarone. This raises amiodarone blood levels and largely shuts down production of its active metabolite, N-desethylamiodarone. The FDA-approved Pacerone label explicitly states grapefruit juice should not be consumed during oral amiodarone treatment.
grapefruit + lurasidone
Lurasidone is metabolized almost entirely by the CYP3A4 enzyme, which makes it highly sensitive to CYP3A4 inhibitors. The FDA-approved Latuda prescribing information states that grapefruit and grapefruit juice should be avoided in patients taking lurasidone, because they inhibit CYP3A4 and can raise lurasidone concentrations.
grapefruit + quetiapine
Quetiapine is metabolized primarily by CYP3A4. Grapefruit juice irreversibly inhibits intestinal CYP3A4 and can substantially increase quetiapine plasma concentrations. A published case report describes quetiapine toxicity in a young woman who consumed a large volume of grapefruit juice over a single day while on a stable dose, with sedation, low blood pressure, and ECG changes that resolved once the juice was stopped.
cyclosporine + grapefruit
Grapefruit contains furanocoumarins that irreversibly inhibit intestinal CYP3A4, the enzyme that normally breaks down cyclosporine before it is absorbed. This meaningfully raises cyclosporine blood levels and, because cyclosporine has a narrow safety margin, increases the risk of kidney injury, high blood pressure, and neurological side effects. The effect persists for about a day or longer after a single serving.
grapefruit + sirolimus
Sirolimus is a CYP3A4 and P-glycoprotein substrate with a narrow therapeutic window and high patient-to-patient variability. The FDA-approved Rapamune label states that grapefruit juice inhibits the CYP3A4-mediated metabolism of sirolimus and must not be taken with, or used to dilute, the drug, because unpredictable rises in blood levels can cause toxicity and threaten the transplanted organ.
grapefruit + buspirone
Grapefruit irreversibly inhibits intestinal CYP3A4, the enzyme that destroys most of an oral buspirone dose before it reaches the bloodstream. In a controlled human study, grapefruit juice substantially raised buspirone blood levels, markedly amplifying drowsiness, dizziness, and lightheadedness.