Drug Interaction Report

GENERALLY AVOID: Some beverages such as tonic water contain varying amounts of quinine. Coadministration of a single 430 mg dose of quinine has been shown to increase plasma concentrations of astemizole and its metabolite, desmethylastemizole. Elevated levels of these agents may cause a prolongation of the electrocardiographic QT interval and potentially fatal ventricular arrhythmias. Although pharmacokinetic data have indicated that the amounts of quinine in beverages (up to 80 mg quinine in 32 oz of tonic water) are not sufficient to produce a significant effect, the potential for an interaction exists if large amounts of tonic water are ingested. Also, grapefruit juice has been shown to inhibit CYP450 enzymes, which may lead to increased serum astemizole concentrations. The risk of life-threatening ventricular arrhythmias may be increased.

MANAGEMENT: Patients should be counseled to limit consumption of quinine-containing beverages and avoid grapefruit juice while they are taking astemizole.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of zolpidem. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

ADJUST DOSING INTERVAL: Administration of zolpidem with food may delay the onset of hypnotic effects. In 30 healthy subjects, administration of zolpidem 20 minutes after a meal resulted in decreased mean peak plasma drug concentration (Cmax) and area under the concentration-time curve (AUC) by 25% and 15%, respectively, compared to fasting. The time to reach peak plasma drug concentration (Tmax) was prolonged by 60%, from 1.4 to 2.2 hours.

MANAGEMENT: Patients receiving zolpidem should be advised to avoid the consumption of alcohol. For faster sleep onset, zolpidem should not be administered with or immediately after a meal.