Chronic toxicity of ebrotidine in rats and dogs

The results obtained in the chronic toxicity studies of ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4-thiazolyl] methyl]thio]ethyl]amino]methylene]-4-bromo-benzenesulfonamide, CAS 100981-43-9, FI-3542) by oral route in rats and in Beagle dogs are reported. Rats were administered for 6 months and dogs for 12 months. The doses were 50, 200 and 500 mg/kg in rats and 50, 200 and 400 mg/kg in dogs. The dose of 400 mg/kg was reduced to 350 mg/kg after 3 months of treatment, due to its toxicity. The effects probably related to the administration of ebrotidine were as follows: three dogs from the high dose group died after 3, 4.5 and 8 months of treatment (in rat there was no mortality); occult blood in faeces; lower weight gain in the high dose group (in rats only females were affected); lower food consumption in rats from the high dose group (and also females from the middle dose group); reduction of erythrocyte count and packed cell volume, only in rats and at the end of the study; alkaline phosphatases increment in rats and dogs; proteinemia decrease in rats; and a tendency to decrease in the testicular weight, which was not statistically significant (p > 0.05). The only histopathological changes observed were moderate erosions or ulcerations in the intestinal mucosa of some dogs from the high dose group. These effects coincide with those published for other competitive H2-receptor inhibitors. The maximum toxic effect-free level was 50 mg/kg for both rats and dogs, which provides a wide safety margin with respect to the therapeutic dose.