Grapefruit

From Anvita Health Wiki

Contents 1 Pharmacokinetics 2 Drug-interactions 3 Mechanism-of-action 4 More General Terms 5 Additional Terms 6 References

Pharmacokinetics

• inhibits cyt P450 3A4 & P-glycoprotein in the GI tract
• hepatic cyt P450 3A4 not affected [7]
• may take 3 days for cyt P450 3A4 enzyme activity to recover

Drug-interactions

• grapefruit inhibits cyt P450 3A4, thus inhibits metabolism of:

• HMG CoA reductase inhibitors:

• atorvastatin (up to 25% increase)
• lovastatin (up to 300% or more increase)
• simvistatin (up to 300% or more increase)
• pravastatin ( Pravachol) & fluvastatin ( Lescol) are NOT metabolized by cyt P450 3A4, thus are unaffected by consumption of grapefruit

• Ca+2 channel blockers

• amlodipine
• diltiazem
• felodipine
• nicardipine
• nifedipine
• nimodipine
• nislodipine
• verapamil

• benzodiazepines

• diazepam
• midazolam
• quazepam
• triazolam

• antiretroviral agents

• amprenavir (probably not significant)
• saquinavir
• indinavir

• immunosuppressants

• cyclosporine
• sirolimus
• tacrolimus

• anticonvulsants

• carbamzepine
• phenytoin

• antiarrythic agents

• amiodarone
• carvediolol
• digoxin
• quinidine

• antibiotics

• clarithromycin
• erythromycin
• telithromycin (no effect)
• itraconazole

• antineoplastic agents

• etoposide

• ARBs

• losartan

• antipsychotics

• haloperidol

• antidepressants

• buspirone
• clomipramine
• fluvoxamine
• sertaline

• endocrine agents

• estrogens
• methylprednisolone
• progesterone

• antihistamines

• fexofenadine

• caffeine
• cisapride
• methdone
• scopalamine
• sildenafil
• theophylline
• cilostazol
• warfarin

Mechanism-of-action

• inhibits cyt P450 3A4 & P-glycoprotein in the GI tract [5]
• increases absorption of pharmaceuticals metabolized by cyt P450 3A4
• one 8 oz glass of grapefruit juice or 1 grapefruit can cause significant drug interactions [5]
• may reduce insulin levels & promote weight reduction by diminishing appetite [6]

More General Terms

• fruit

Additional Terms

• cytochrome P450 3A4 (cytochrome P450 C3, nifedipine oxidase, P450-PCN1, NF-25, CYP3A4)

References

1. Kaiser Permanente Northern California Regional Memo, 12/99
2. url>http://www.powernetdesign.com/grapefrut/</url>
3. Prescriber's Letter 6(10):55, Oct, 1999
4. Prescriber's Letter 13(3): 2006 Cytochrome P450 drug interactions Detail-Document#: [1] (subscription needed) [2]
5. Prescriber's Letter 9(9):54, Sept, 2002
6. CBS Healthwatch from Netscape (Feb 9, 2004) research from Fujioka K. Scripps Metabolic Research Center, Scripps Clinic cited
7. Prescriber's Letter 14(2): 2007 Potentional drug interactions with grapefruit Detail-Document#: [3] (subscription needed) [4]
8. Prescriber's Letter 18(3): 2011 CHART: Potential Drug Interactions with Grapefruit Detail-Document#: [5] (subscription needed) [6]

grapefruit