Drug Interaction Report

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of sertraline. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills. In addition, limited clinical data suggest that consumption of grapefruit juice during treatment with sertraline may result in increased plasma concentrations of sertraline. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism by certain compounds present in grapefruit. An in-vitro study demonstrated that grapefruit juice dose-dependently inhibits the conversion of sertraline to its metabolite, desmethylsertraline. In a study with eight Japanese subjects, mean plasma levels of sertraline increased by approximately 100% and maximum plasma concentrations increased by 66% after the ingestion of three 250 mL glasses of grapefruit juice per day for 5 days and administration of a single dose of sertraline 75 mg on the sixth day. In another small study with 5 patients, mean sertraline trough levels increased by 47% after taking sertraline for at least 6 weeks, then taking sertraline with 240 mL grapefruit juice daily for 1 week. The clinical significance is unknown; however, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability. The possibility of significant interaction in some patients should be considered.

MANAGEMENT: Patients receiving sertraline should be advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how sertraline affects them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities. Some authorities recommend that consumption of grapefruit juice should be avoided during sertraline therapy.

GENERALLY AVOID: Coadministration with large amounts of certain fruit juices, including grapefruit, orange and apple, may decrease the oral bioavailability of fexofenadine. The proposed mechanism is inhibition of drug efflux via intestinal organic anion transporting polypeptides (e.g., P-glycoprotein), of which fexofenadine is a substrate. In a five-way crossover study with 10 healthy volunteers, 1/4-strength grapefruit juice, grapefruit juice, orange juice and apple juice (300 mL with drug administration and 150 mL every 1/2 hour for up to 3 hours, total volume 1.2 L) reduced the mean area under the plasma concentration-time curve (AUC) of a 120 mg dose of fexofenadine by 23%, 67%, 72% and 77%, respectively, compared to water. Mean peak plasma concentration (Cmax) was similarly affected. The clinical significance of these changes is unknown. However, results from studies using histamine-induced skin wheals and flares found that the size of wheal and flare was significantly larger when fexofenadine was administered with either grapefruit or orange juices compared to water.

MANAGEMENT: To maximize plasma levels and therapeutic effects, fexofenadine should be taken with water. In addition, patients should refrain from consuming large amounts of grapefruit, orange, or apple juice.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.