INTERACTIONS OF GRAPEFRUIT WITH MEDICATIONS

Grapefruit Juice and Psychiatric Medications

Several psychiatric medications are affected by the metabolism of cytochrome p450 isoenzyme 3A4 (CYP3A4). The bioavailability was affected. A significant increase in pharmacodynamic effects, such as prolonged reaction times was also observed. The interactions could have important implications in patients with other conditions that might increase benzodiazepine bioavailability (e.g. advanced age, liver cirrhosis, concurrent use of other medications that inhibit cytochrome P450). These patients should be observed for increased sedation.

Triazolam (Halcion)
 
Triazolam AUC was increased 48% and Cmax increased 30% in healthy volunteers given triazolam with grapefruit juice. Drowsiness was significantly increased when triazolam was given concurrently with grapefruit juice. (Source: Hukkinen SK, Varhe A, Olkkola KT et al.,  Clin Pharmacol Ther 1995; 58: 127-31).

Diazepam (Valium)

Eight healthy subjects were given diazepam 5mg orally with either 250 mL water or grapefruit juice. The mean AUC of diazepam was increased 3.2-fold and the peak concentration was increased 1.5-fold by the grapefruit juice. Grapefruit juice postponed the time to reach peak concentration of diazepam from 1.5 hours to 2.1 hours. (Reference: Ozdemir M, Aktan Y, Boydag BS.,  Eur J Drug Metab Pharmacokinet 1998 Jan-Mar;23(1):55-9.)

Alprazolam (Xanax)

Alprazolam is a substrate of CYP3A4, and may be subject to similar increases in AUC and clinical effects as seen with the other CYP3A4-metabolized benzodiazepines.

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