Gas-chromatographic analysis of 4-prenyl-1,2-diphenyl-3-5-pyrazolidinedione (feprazone) at therapeutic levles in human plasma.

A specific and sensitive procedure for the determination of prenazone at therapeutic levels in human plasma has been developed. The method involves extraction of the drug from acidified plasma into chloroform. After further purification by back extraction the residue is examined on a gas-liquid chromatograph fitted with a flame ionisation detector. Tetraphenylethylene is used as an internal standard for quantitation by the relative peak height technique. Plasma levels encountered after oral ingestion of therapeutic doses are reported.