Abstract
1. One of the main metabolites of [14C]trazodone hydrochloride by rat liver in vitro is hydroxylated trazodone.
2. [14C]Trazodone HCI is absorbed very rapidly and the blood level of radioactivity attains a maximum within 15 min after oral administration of 4 mg/kg to rats and thereafter decreases rapidly.
3. Urinary and faecal excretions of radioactivity are 49.0 and 46.1% of the dose respectively, during the first 7 days after ingestion, and biliary excretion is 80.0% in 8 h.
4. After oral administration of [14C]trazodone HCI to rats the main metabolites in urine and bile are hydroxylated trazodone, β-{3-oxo-s-triazolo[4,3a]-pyridin-2-yl}-propionic acid and their glucuronides.
5. Unchanged and hydroxylated trazodone alone are present in brain of rats after oral administration (20 mg/kg); both compounds in brain decrease with similar half-lives to those in plasma.