Pharmacokinetics/Pharmacodynamics of Desloratadine and Fluoxetine in Healthy Volunteers

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The authors assessed the potential for a pharmacokinetic/pharmacodynamic interaction between desloratadine and fluoxetine. This randomized, placebo-controlled, open-label study was conducted in 54 healthy volunteers. Subjects received 1 of 3 treatments: desloratadine 5 mg plus fluoxetine 20 mg, desloratadine 5 mg plus placebo, or fluoxetine 20 mg plus placebo. Serial electrocardiograms (ECGs) were performed at baseline and day 35. Treatment effects on Cmax and AUC were assessed. During coadministration of desloratadine with fluoxetine, the ratio of the mean log-transformed Cmax and AUC values for desloratadine following concomitant fluoxetine therapy revealed a small increase in Cmax values of 15% (90% confidence interval [CI], 95%-139%)butno increase for AUC values (90% CI, 82%-123%). Corresponding values for 3-OH desloratadine demonstrated small increases in mean log-transformed Cmax and AUC ratios: 17% (90% CI, 100%-136%) and 13% (90% CI, 96%-132%), respectively. Statistical evaluation of the ratio of the mean Cmax and AUC values for fluoxetine following concomitant desloratadine therapy revealed small decreases of 9% (90% CI, 72%-115%) and 11% (90% CI, 69%-113%), respectively. Corresponding values for norfluoxetine demonstrated modest increases in mean log-transformed Cmax and AUC ratios: 22% (90% CI, 100%-139%) and 18% (90% CI, 101%-136%), respectively. Coadministration of desloratadine with a potent inhibitor of CYP2D6 did not result in clinically relevant changes in its pharmacokinetic parameters. Desloratadine administration was not associated with clinically important changes in the pharmacokinetics of fluoxetine, a drugmetab-olized by CYP2D6. The most common adverse event in all groups was headache (65%). Desloratadine plus fluoxetine caused no significant changes in ECGs or ventricular rate.

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