Prevalence of desloratadine poor metabolizer phenotype in healthy Jordanian males.

To study the prevalence of desloratadine slow metabolizer phenotype among a group of healthy Jordanian male volunteers. A total of 62 healthy Jordanian male volunteers were included in this study. A single 5 mg desloratadine oral tablet was given and blood samples were taken to determine the desloratadine and 3-hydroxydesloratadine (3-OH-desloratadine) concentrations using a specific liquid chromatography-mass spectrometric method (LC/MS/MS). The determination of pharmacokinetic parameters of all the individuals was determined by using Kinetica® program version 4.1. Poor metabolizers or slow metabolizers of desloratadine were determined as individuals having a 3-OH-desloratadine to desloratadine exposure ratio lower than 10% or a desloratadine half-life ≥ 50 h. Among the 62 volunteers who participated in the study there were only two volunteers who were labeled as desloratadine slow metabolizers, giving a prevalence of 3.2%. The maximum plasma concentrations (C(max)) were similar in the extensive and slow metabolizers groups but a longer time (t(max)) was needed to achieve this concentration in one of the volunteers who was a desloratadine slow metabolizer. The incidence of the poor metabolizer phenotype of desloratadine in the Jordanian population studied is similar to certain ethnic groups (e.g. Asian, Caucasians and Hispanic); however, it is lower than other populations (e.g. American Indians and Black).