Studies on metabolism of trazodone. III Species differences.

1. After oral administration of (14C) trazodone HCl (4 mg/kg) to rabbits, the blood level of radioactivity shows a peak at 3 h; unchanged trazodone concentration in brain is higher than that in plasma at 3 h after dosage. 29 The metabolic fate of trazodone in rabbits is different from that in rats and a new, basic metabolite is present in rabbit liver, brain, plasma and urine. 3. The concentration pattern in blood of humans given a single dosage (50 mg) of trazodone HCl is similar to that in rabbits rather than that in rats. 4. The rate of metabolism of trazodone by liver microsomes from mice is approximately 1-5 times higher than that with rat or rabbit liver microsomes.