Carcinogenesis bioassay of prazepam (Verstran) in rats and mice.

Abstract The carcinogenesis potential of the benzodiazepine derivative prazepam was studied for 104 and 80 weeks in rats and mice, respectively. Groups of rats and mice of both sexes received 75, 25, and 8 mg/kg/day as dietary admixtures over the entire experimental period. Adequate survival rates allowed adequate statistical treatment of diagnosed neoplasia. The compound failed to elicit increased tumor rates or changes in the average latency or onset in both species. Diazepam, used as reference control at 75 mg/kg/day, also failed to show elevated tumor incidences. Most common tumors found represented spontaneous neoplasia correlating with the background of these strains. Although carcinogenic studies with this category of drugs do not abound in the literature, an earlier report indicated that oxazepam produced benign liver tumors and peliosis hepatis in mice. These results have not been confirmed and studies in rats have not been published. From the data reported here, it was concluded that prazepam does not show positive tumorigenic potential. The safety of this compound cannot be extrapolated to structurally related compounds in this series because of the lack of supportive evidence with available agents.