title: Metabolism of 14C-estazolam in dogs and humans.
abstract: 14C-Estazolam (2 mg) administered orally to dogs and human subjects was rapidly and completely absorbed with peak plasma levels occurring within one hour. In humans, plasma levels peaked at 103 +/- 18 ng/ml and declined monoexponentially with a half-life of 14 h. The mean concn. of estazolam in dog plasma at 0.5 h was 186 ng/ml. Six metabolites were found in dog plasma at 0.5 and 8 h, whereas only two metabolites were detected in human plasma up to 18 h. Metabolites common to both species were 1-oxo-estazolam (I) and 4-hydroxy-estazolam (IV). Major metabolites in dog and human plasma were free and conjugated 4-hydroxy-estazolam; the concn. were higher in dogs. After five days, 79% and 87% of the administered radioactivity was excreted in dog and human urine, respectively. Faecal excretion accounted for 19% of the dose in dog and 4% in man. Eleven metabolites were found in the 0-72 h urine of dogs and humans; less than 4% dose was excreted unchanged. Four metabolites were identified as: 1-oxo-estazolam (I), 4'-hydroxy-estazolam (II), 4-hydroxy-estazolam (IV) and the benzophenone (VII), as free metabolites and glucuronides. The major metabolite in dog urine was 4-hydroxy-estazolam (20% of the dose), while the predominant metabolite in human urine (17%) has not been identified, but is likely to be a metabolite of 4-hydroxy-estazolam. The metabolism of estazolam is similar in dog and man.
authors.forename: J M
authors.initials: JM
authors.lastname: Machinist
authors.forename: B A
authors.initials: BA
authors.lastname: Bopp
authors.forename: D J
authors.initials: DJ
authors.lastname: Anderson
authors.forename: G R
authors.initials: GR
authors.lastname: Granneman
authors.forename: R C
authors.initials: RC
authors.lastname: Sonders
authors.forename: K
authors.initials: K
authors.lastname: Tolman
authors.forename: K
authors.initials: K
authors.lastname: Buchi
authors.forename: D
authors.initials: D
authors.lastname: Rollins
mesh_terms: D000284:Administration, Oral; D000818:Animals; D014151:Anti-Anxiety Agents / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D004949:Estazolam / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005243:Feces / Q000032:analysis; D005260:Female; D006207:Half-Life; D006801:Humans; D007275:Injections, Intravenous; D008297:Male
chemical_list: D014151:Anti-Anxiety Agents; D002250:Carbon Radioisotopes; D004949:Estazolam