The metabolism of radioactive pentobarbital in mice.

The synthesis of radioactive urea (Cr4) of high specific activity* permits one to trace the metabolism of urea and many of its readily synthesized derivatives, i.e. the barbiturates. The universal use of the barbiturates in clinical medicine makes an investigation of their metabolism in the animal of interest. Pentobarbital sodium (nembutal) (tagged with C4, specific activity 8400 counts per second per mg.) has been prepared in these laboratories from radioactive urea.’ The metabolism of this compound has been the subject of repeated investigation both in vivo and in vitro. Recently the problem has been attacked by van Dyke, Scudi, and Tabern (1) who used the N15labeled compound. However, since the compound labeled with Cl4 affords greater sensitivity and accuracy in the analytical methods, the results of our investigation are reported here.