A radioimmunoassay combined with solid-phase extraction for the determination (pg ml −1) of AR-C15849XX in human plasma

A radioimmunoassay has been developed for the determination of AR-C15849KF, a CCK-8 analogue, in human plasma. The method incorporates solid-phase sample extraction, is suitable for the determination of the analyte at pg ml −1 concentrations and is based on a method developed and validated for dog plasma. The solid-phase extraction, using ion-exchange aminopropyl and octadecyl sorbents sequentially, was retained for this procedure to remove matrix interferences in the plasma and to enhance method sensitivity. The calibration range is 10–500 pg ml −1, using a 1 ml sample of undiluted human plasma. The method has been successfully used to generate early human pharmacokinetic data during a programme of exploratory development.