High-performance liquid chromatographic determination of the mucoregulatory drug CO/1408 in rat plasma and urine.

A sensitive and selective high-performance liquid chromatographic (HPLC) method was developed for the determination of the mucoregulatory drug CO/1408 in plasma and urine. Samples containing an internal standard were prepared for analysis using a simple clean-up procedure based on Extrelut solid-phase extraction and chromatographed using a reversed-phase analytical column. Isocratic elution with a mobile phase consisting of 25 mM phosphate buffer (pH 2.5)-acetonitrile-methanol [85:10:5 or 87:9:4 (v/v) for plasma or urine analysis, respectively] was effected at a flow-rate of 0.8 ml/min. The eluate was monitored with an ultraviolet-visible variable-wavelength detector at 200 nm. The limit of quantification for the assay of CO/1408 was 80 ng/ml for plasma and 1 per 0.1 ml for urine samples. In spite of the high solubility of CO/1408 in water, the recovery from plasma and urine was very good and reproducible. The method was found to be applicable to pharmacokinetic studies of the drug in the rat.