Potential pharmacokinetic interaction (increased plasma concentrations of desloratadine and active metabolite) when desloratadine is used with drugs affecting hepatic microsomal enzymes (e.g., azithromycin, cimetidine, erythromycin, fluoxetine, ketoconazole). No clinically important changes in ECG or laboratory evaluations, vital signs, or adverse effects were reported. Grapefruit juice, Pharmacokinetic interaction unlikely (for syrup only).