Drug Interactions between loratadine and Zoloft

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.

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Theoretically, grapefruit juice may increase the plasma concentrations of loratadine as it does other drugs that are substrates of the CYP450 3A4 enzymatic pathway. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The clinical significance of this potential interaction is unknown. Reported interactions with potent CYP450 3A4 inhibitors like clarithromycin, erythromycin and ketoconazole have produced substantial increases in the area under the plasma concentration-time curve (AUC) of loratadine and its active metabolite, descarboethoxyloratadine, without associated changes in the overall safety profile of the drug.

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