Rapid and sensitive high-performance liquid chromatographic assay for nalbuphine in plasma

A simple and reliable reversed-phase high-performance liquid chromatographic method with adequate internal analog standardization and coulometric detection is described for the quantification of nalbuphine in plasma samples. The lower limit of detection was estimated to be 0.1 ng/ml. For routine analysis, the limit of quantification was set at 0.5 ng/ml and only a small plasma volume (500 microliters) was required. The nalbuphine calibration curve was linear over the concentration range 0-100 ng/ml. The recoveries of nalbuphine and 6-monoacetylmorphine, used as internal standard, were close to 85%. Due to the small sample volume of blood required, this highly sensitive, accurate and specific method is suitable for pharmacokinetic studies of nalbuphine, and particularly for drug monitoring in neonates born from mothers treated with nalbuphine.