Determination of diethylcarbamazine, an antifilarial drug, in human urine by H-1-NMR spectroscopy

H-1-NMR spectroscopy is a convenient method for determination of diethylcarbamazine (DEC) in urine, and can be used to monitor medication with the drug. Urine samples were mixed with 10%, of deuterium oxide as a spectrometer field frequency lock, which is the only sample pretreatment required. Tailored excitation with the 1 (3) over bar 3 (1) over bar pulse was used for water peak suppression. The quantification of DEC was carried out with the triplet of the N-ethyl group, for which the T-1 relaxation rime was 1 s. In aqueous solutions, amounts below 1 mu g ml(-1) of DEC could be easily detected. In urine, the detectability depended on the level of chemical noise but was better than 10 mu g ml(-1). The accuracy and precision of the method were better than 15%. Analysis of urine from volunteers receiving a single therapeutic dose of DEC (6 mg kg(-1) body weight orally) showed that the drug was eliminated in unchanged form during 2 days, in agreement with earlier results. The concentration of DEC in urine several hours after the intake exceeded 100 mu g ml(-1) making the H-1-NMR assay rapid and easy. No significant amounts of the N-oxide of DEC could be detected.