A systematic investigation of the disposition of acetylmethadol (AM) in rat, rabbit and man is designed to provide comparative information on the rates, pathways and routes of elimination in these three species. Plasma time course and tissue distribution of AM and metabolites will be measured following acute and chronic drug administration to rats and rabbits. Maternal and fetal disposition will be compared to pregnant rabbits. Patricular emphasis will be directed toward the identification of persistent metabolites in brain and liver tissue. Methods used in these studies will include radioisotope-labeling, gas-liquid chromatography and mass spectrometry. These methods together with solvent extraction, thin-layer and column chromatography will provide qualitative and quantitative information on the disposition of AM in these species.