Grapefruit juice

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Grapefruit juice
Sliced pink grapefruit

Grapefruit juice is the juice from grapefruits.

It is rich in Vitamin C and ranges from sweet-tart to very sour. Variations include white grapefruit, pink grapefruit and ruby red grapefruit juice.[1][2]

Grapefruit juice is important in medicine because of its interactions with many common drugs including caffeine and medications, which can alter how they behave in the body.

Drug interactions[edit]

Grapefruit juice, and grapefruit in general, is a potent inhibitor of cytochrome P450 enzymes, principally the CYP3A4 isoform. This can affect the metabolism of a variety of drugs and increase their bioavailability.[3][4][5][6][7] In some cases, this can lead to a fatal interaction with drugs like astemizole or terfenadine.[4] The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. The first published report on grapefruit drug interactions was in 1991 in the Lancet entitled "Interactions of Citrus Juices with Felodipine and Nifedipine," and was the first reported food-drug interaction clinically. However, the effect only became well-publicized after being responsible for a number of bad interactions with medication.[8]

Recently some researchers have shown that furanocoumarins rather than flavonoids are the ingredients causing the various drug interactions.[9][10]

Grapefruit juice has also been reported to increase both the bioavailability of some benzodiazepines, (such as diazepam) and greatly slow the rate of metabolization.[11] An easy way to tell if a medication may be affected by grapefruit juice is by researching whether another known CYP3A4 inhibitor drug is already contraindicated with the active drug of the medication in question. Examples of such known CYP3A4 inhibitors include cisapride (Propulsid),[citation needed] erythromycin, itraconazole (Sporanox), ketoconazole (Nizoral),and mibefradil (Posicor).[12]

The flavonoid existing in highest concentration in grapefruit juice is naringin, which in humans is metabolised to naringenin. Other flavonoids exist in grapefruit juice in lower concentrations as well. Orange juice does not contain naringin in as high a concentration, instead containing hesperetin. It is sometimes recommended as a substitute. Juice of limes and Seville oranges can also inhibit drug metabolism, however, as can apple juice with some drugs.[10]

See also[edit]


  1. ^ The World's Healthiest Foods; Grapefruit. The George Mateljan Foundation. Article
  2. ^ Fellers PJ, Nikdel S, Lee HS (August 1990). "Nutrient content and nutrition labeling of several processed Florida citrus juice products". Journal of the American Dietetic Association 90 (8): 1079–84. PMID 2380455. 
  3. ^ He K, Iyer KR, Hayes RN, Sinz MW, Woolf TF, Hollenberg PF (April 1998). "Inactivation of cytochrome P450 3A4 by bergamottin, a component of grapefruit juice". Chemical Research in Toxicology 11 (4): 252–9. doi:10.1021/tx970192k. PMID 9548795. 
  4. ^ a b Bailey DG, Malcolm J, Arnold O, Spence JD (August 1998). "Grapefruit juice–drug interactions". British Journal of Clinical Pharmacology 46 (2): 101–10. doi:10.1046/j.1365-2125.1998.00764.x. PMC 1873672. PMID 9723817. 
  5. ^ Garg SK, Kumar N, Bhargava VK, Prabhakar SK (September 1998). "Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy". Clinical Pharmacology and Therapeutics 64 (3): 286–8. doi:10.1016/S0009-9236(98)90177-1. PMID 9757152. 
  6. ^ Bailey DG, Dresser GK (2004). "Interactions between grapefruit juice and cardiovascular drugs". American Journal of Cardiovascular Drugs 4 (5): 281–97. doi:10.2165/00129784-200404050-00002. PMID 15449971. 
  7. ^ Bressler R (November 2006). "Grapefruit juice and drug interactions. Exploring mechanisms of this interaction and potential toxicity for certain drugs". Geriatrics 61 (11): 12–8. PMID 17112309. 
  8. ^ Bakalar, Nicholas. Experts Reveal the Secret Powers of Grapefruit Juice. New York Times. Published: March 21, 2006
  9. ^ [1]
  10. ^ a b Bakalar, Nicholas (2006-03-21). "Experts Reveal the Secret Powers of Grapefruit Juice". The New York Times. p. F6. Retrieved 2006-11-21. 
  11. ^ Ozdemir M, Aktan Y, Boydag BS, Cingi MI, Musmul A (1998). "Interaction between grapefruit juice and diazepam in humans". European Journal of Drug Metabolism and Pharmacokinetics 23 (1): 55–9. doi:10.1007/BF03189827. PMID 9625273. 
  12. ^ "Wake Forest Baptist Medical Center" (PDF). 

External links[edit]