[Pharmacokinetics and metabolism of trazodone in man (author's transl)]

After intravenous, intramuscular and oral administration of 25 mg 14C-labelled 2-(3-[4-(m-chlorophenyl)-1-piperazinyl]-propyl)-s-triazolo[4,3-a]pyridin-3-(2H)-one-hydrochloride (trazodone), plasma levels, elimination and metabolite pattern in plasma and urine were investigated. The plasma levels after all routes of administration are almost identical. The absorption of the compound is fast and complete. The elimination of radioactivity occurs in a biphasic manner with a half-life of 1 h for the earlier and 13 h for the second phase, no matter what application route had been chosen. The comparison of the plasma levels of fasted and non-fasted subjects shows a shift of the plasma maximum from 1.5 to 2.5 h following administration and a decrease in the maximum level of 30%. The radioactivity is excreted predominantly by renal processes (70-75% within 72 h). The main product in plasma is unchanged trazodone, whereas in urine it is found only in minute amounts. The radioactivity in urine is represented by conjugates that had formed after hydroxylation on the chlorophenyl residue (20%), by a dihydrodiol-metabolite of trazodone (15%) and by a carboxylic acid originating from oxidative cleavage of the parent compound (35%).