In vivo metabolism of [4-13C]phenacetin in an isolated perfused rat liver measured by continuous flow 13C NMR spectroscopy.

Continuous flow 13C NMR spectroscopy has been used for the first time to monitor the metabolism of a 13C labeled drug in an isolated liver. Continuous and almost immediate information on the metabolite formation could be obtained using 13C labeled phenacetin without alteration of the biological system. The data are consistent with those observed by conventional techniques (HPLC, aliquot 13C NMR measurements). From the biological point of view the sensitivity of continuous flow 13C NMR spectroscopy is still low (10(-3) M). The results presented demonstrate however that non-invasive and non-radioactive real time monitoring of drug metabolism in intact organs is possible.