Effect of storage on the plasma concentration of chlorpromazine and six of its metabolites.

The concentrations of chlorpromazine (CPZ) and six of its metabolites in patient plasma samples that had been stored for 24 h at -20 degrees C, for 1 week at -20 degrees C, and for 4 weeks at -70 degrees C were compared. The concentrations of CPZ and six of its metabolites in human plasma spiked with known concentrations and stored at -70 degrees C for either 3 or 12 months were also compared. No significant difference was seen in the concentrations after storage under nitrogen and analysis by a high-performance liquid chromatography technique.