Interaction between grapefruit juice and diazepam in humans

Area of Science:

• Pharmacology
• Drug Metabolism
• Nutritional Science

Background:

• Grapefruit juice is known to enhance the bioavailability of various drugs metabolized by cytochrome P450 3A4 (CYP3A4).
• Previous studies indicate interactions with drugs like cyclosporine and calcium channel blockers.
• The specific impact of grapefruit juice on diazepam pharmacokinetics requires further investigation.

Purpose of the Study:

• To investigate the effect of grapefruit juice on the plasma concentrations of diazepam.
• To determine if grapefruit juice alters the absorption and disposition of diazepam.

Main Methods:

• Eight healthy subjects (male and female) participated in the study.
• Subjects received an oral 5 mg dose of diazepam with either water or grapefruit juice.
• Whole blood diazepam concentrations were measured via enzyme immunoassay over a 24-hour period.

Main Results:

• Grapefruit juice increased the area under the diazepam concentration-time curve (AUC(0-24)) by 3.2-fold (P < 0.001).
• The maximum plasma concentration (Cmax) of diazepam was elevated by 1.5-fold (P < 0.05) with grapefruit juice.
• Grapefruit juice significantly postponed the time to maximum concentration (tmax) from 1.50 h to 2.06 h (P < 0.01).

Conclusions:

• Grapefruit juice significantly alters diazepam pharmacokinetics, increasing its systemic exposure.
• The consumption of grapefruit juice with diazepam may lead to increased drug effects or side effects.
• This interaction highlights the importance of considering dietary factors in drug therapy.