Liquid-chromatographic assay of diazepam and its major metabolites in serum, and application to pharmacokinetic study of high doses of diazepam in schizophrenics.

In this rapid, sensitive method for simultaneously determining diazepam and its biologically active metabolites--nordiazepam, oxazepam, and temazepam--in serum, 250 to 1000 microL of serum is extracted with ether and the extracted compounds are quantified by "high-performance" liquid chromatography on a Shimpack FLC-C8 microparticulate column. Absorbance of the effluent is monitored at 254 nm. The limit of detection in serum is about 10 micrograms/L for each drug. Analytical recovery of each drug added to the serum varied from 91 to 102% for oxazepam and temazepam, from 82 to 99% for nordiazepam and diazepam. Within-day and between-day CVs ranged from 2 to 5% for oxazepam and temazepam, and from 2 to 7% for nordiazepam and diazepam. We also report results on using this assay in a pharmacokinetic study of high doses of diazepam used to treat chronic schizophrenic patients.