Liquid chromatography–mass spectrometry analysis of diethylcarbamazine in human plasma for clinical pharmacokinetic studies

A sensitive and selective liquid chromatographic method using mass spectrometric detection was developed for the determination of diethylcarbamazine (DEC) in human plasma. DEC and its stable isotope internal standard d3-DEC were extracted from 0.25 mL of human plasma using solid phase extraction. Chromatography was performed using a Phenomenex Synergi 4μ Fusion-RP column (2 mm × 250 mm) with gradient elution. The retention time was approximately 4.8 min. The assay was linear from 4 to 2200 ng/mL. Analysis of quality control samples at 12, 300, and 1700 ng/mL (N = 15) had interday coefficients of variation of 8.4%, 5.4%, and 6.2%, respectively (N = 15). Interday bias results were −2.2%, 6.0%, and 0.8%, respectively. Recovery of DEC from plasma ranged from 84.2% to 90.1%. The method was successfully applied to clinical samples from patients with lymphatic filariasis from a drug–drug interaction study between DEC and albendazole and/or ivermectin.