The absorption, distribution, excretion, and metabolism of a single oral dose of O-ethyl O-4-nitrophenyl phenylphosphonothioate in hens.

The disposition and metabolism of a single oral 10 mg/kg (LD50) of uniformly phenyl-labeled [14C]EPN (O-ethyl O-4-nitrophenyl [14C]phenylphosphonothioate) were studied in adult hens. The birds were protected from acute toxicity with atropine sulfate. Three treated hens were killed at each time interval (days): 0.5, 2, 4, 8, 12. Radioactivity was adsorbed from the gastrointestinal tract and distributed in all tissues. Most of the dose was excreted in the combined urinary-fecal excreta (74%). Only traces of the radioactivity (0.2%) were detected in expired CO2. Most of the excreted radioactive materials were identified as phenylphosphonic acid (PPA), O-ethyl phenylphosphonic acid (EPPA), and O-ethyl phenylphosphonothioc acid (EPPTA). Radioactivity in tissues reached a peak of 11.8% in 12 days. The highest concentration of radioactivity was present in the liver followed by bile, kidney, adipose tissue, and muscle. EPN was the major compound identified in brain, spinal cord, sciatic nerve, kidney, and plasma. Most of the radioactivity in the liver was identified as EPPA followed by EPPTA and PPA. Kinetic studies showed that EPN disappeared exponentially from tissues. The half-life of the elimination of EPN from plasma was 16.5 days corresponding to a constant rate value of 0.04 day-1. Relative residence (RR) of EPN relative to plasma was shortest in liver and longest in adipose tissue followed by sciatic nerve and spinal cord.