High speed liquid chromatography, 14C-radioassay and spectrophotometry for measuring antipyrine plasma half-life in rhesus monkeys (Macaca mulatta).

6 male rhesus monkeys (Macaca mulatta) were treated with 14CH3-N-antipyrine (15 mg/kg, i.v.). Antipyrine plasma half-lives (APH) were determined using HSLC, radiometric, and spectrophotometric methods. APHs obtained by HSLC analysis of plasma extracts were lower than radiometric and spectrophotometric determinations. The three procedures were investigated to determine if coextraction of metabolites might be responsible for differences in APH. All three solvent systems extract significant quantities of antipyrine metabolites. N-desmethylantipyrine and 3-hydroxymethylantipyrine may interfere with spectrophotometric determination of antipyrine. While all three methods are capable of detecting changes in hepatic oxidative metabolism, HSLC permits direct measurement of antipyrine concentrations and APH.