Grapefruit Extract (generic name)

treats Atopic eczema, Endocrine disorders, Heart disease, and Kidney stones
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Interactions

Interactions with Drugs

Grapefruit juice may interfere with the way the body breaks down certain drugs in the liver. As a result, the levels of some drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. Patients using medications such as amitriptyline, clomipramine, clozapine, cyclobenzaprine, haloperidol, naproxen, ondansetron, propranolol, theophylline, and verapamil should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Grapefruit juice may also interact with nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., diclofenac, ibuprofen, meloxicam, piroxicam), oral antidiabetic agents (tolbutamide, glipizide), and angiotensin II blockers (e.g., losartan).

Caution is advised when mixing grapefruit juice with proton pump inhibitors (e.g., lansoprazole, omeprazole, pantoprazole), anti-epileptics (e.g., diazepam, phenytoin), carisoprodol, citalopram, and nelfinavir.

Grapefruit juice may increase drug levels and the risk of adverse effects when taken with macrolide antibiotics (e.g., erythromycin, clarithromycin), anti-arrhythmics (e.g., quinidine), benzodiazepines (e.g., alprazolam, midazolam, diazepam, triazolam), immune modulators (e.g., cyclosporine, tacrolimus), protease inhibitors (e.g., ritonavir, saquinavir), prokinetic agents (e.g., cisapride), antihistamines (e.g., terfenadine), calcium channel blockers (e.g., amlodipine, felodipine, diltiazem), HMG-CoA reductase inhibitors (e.g., atorvastatin, lovastatin), alfuzosin, etc.

Although not well studied in humans, numerous other potential interactions with grapefruit juice may occur with acebutolol, alfentanil, alprazolam, amlodipine, amprenavir, anthelmintics (e.g., praziqauntel), antiarrhythmics (e.g., amiodarone, propafenone, quinidine), anticonvulsants (e.g., carbamazepine), antifungal agents (e.g., itraconazole), antimalarial agents (e.g., halofantrine, artemether, quinine), antineoplastic agents, aripiprazole, atorvastatin, beta-blocking agents, benzodiazepines, budesonide, celiprolol, digoxin, eplerenone, etoposide, felodipine, fentanyl, hormone replacement, imatinib, indinavir, lovastatin, levothyroxine, oral contraceptives (e.g., estradiol, progesterone), methylprednisolone, mifepristone, nifedipine, nimodipine, nitrendipine, opioids, pranidipine, ranolazine, scopolamine, selective serotonin reuptake inhibitors (e.g., sertraline), simvastatin, sufentanilbuspirone, sunitinib, talinolol, tolterodine, trazadone, triazolam, and zolpidem. Check with a qualified healthcare professional, including a pharmacist, for any interactions.

Grapefruit may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Grapefruit has been shown to modestly increase the absorption of sildenafil, an erectile dysfunction agent. Theoretically, grapefruit may have similar effects if used with other erectile dysfunction agents, such as tadalafi or vardenafil.

Clinical studies show that the ingestion of grapefruit juice should not cause any pharmacokinetic or pharmacodynamic interactions when coadministered with caffeine.

Grapefruit may reduce the effectiveness of antihistamines such as fexofenadine.

Theoretically, grapefruit juice may inhibit the hepatic metabolism of oxybutynin leading to increased drug levels and associated adverse events.

Grapefruit juice was found to have no significant effect on the metabolism of prednisone or prednisolone in one study of kidney transplant patients.

Based on laboratory study, grapefruit may inhibit the absorption of vinblastine or alter the permeation of vincristine across the blood-brain barrier.

Interactions with Herbs and Dietary Supplements

Theoretically, grapefruit may increase the adverse effects associated with antiarrhythmic, anticonvulsant, antihistamine, immunosuppressant, anti-cancer, beta-blocking, or estrogen-containing herbs and supplements. Concomitant use of grapefruit and green tea may increase caffeine levels leading to an increased risk of cardiovascular and central nervous system stimulatory effects, along with other caffeine-related adverse effects due to caffeine in green tea. However, currently, this effect has not been reported in humans.

In theory, grapefruit juice may increase concentrations of digitalis (foxglove) and vitamin C levels, although clinical significance is unknown.

Theoretically, grapefruit may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

Preliminary evidence suggests that grapefruit juice may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of other herbs or supplements may become too high in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system.

Grapefruit may interfere with the body's conversion of cortisol to cortisone. If both licorice and grapefruit are taken together, the risk of high blood pressure and other side effects may be increased.

Grapefruit juice has a weak interaction with theophylline-containing drugs. In theory, grapefruit may interact with xanthine-containing herbs and caution is advised.

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