Abstract

Biliary excretion of diazepam and its possible enterohepatic circulation were investigated in the rat. During 4 hr, 77% of the radioactivity injected in the form of [5-¹⁴C]diazepam appeared in bile. Radioactivity was eliminated in bile with a half-life of 0.85 hr. Radioactivity in blood in bile-cannulated and control rats declined at essentially the same rate, and blood levels in both groups were not significantly different. This suggested the lack of enteral absorption. Urinary excretion was negligible. No diazepam could be detected in bile; the radioactivity consisted mostly of conjugated metabolites of diazepam. It was concluded that there was virtually no enterohepatic circulation of diazepam in the rat.