An automated biological assay to determine levels of the trypanocidal drug melarsoprol in biological fluids

For the investigation of the pharmacokinetic properties of a drug, methods for sensitive and precise quantification are a prerequisite. Only few functional methods exist for the determination of the trypanocidal drug melarsoprol in biological fluids: A bioassay which requires microscopical evaluation and two HPLC methods, which require sample extraction and are difficult to automatize due to the drug’s properties. We report the development of an automated biological assay, based on the fluorescent dye Alamar blue®. To validate the assay for melarsoprol, 108 serum and 37 cerebrospinal fluid (CSF) samples were spiked with melarsoprol at concentrations of 17–92 ng/ml for CSF and 17 ng/ml–2.2 μg/ml for serum. The precision (repeatability) expressed as the interday average coefficient of variation was 9.9% for serum and 18.8% for CSF samples over the respective concentration range. The accuracy (measurement for the systematic error) of the test was 99.4% for serum and 96.4% for CSF. The assay’s limit of quantitation with the use of the trypanosome stock STI 704 BABA was 4 ng/ml for both serum and CSF samples.