Promotion of rat hepatocarcinogenesis by praziquantel.

Praziquantel, the widely used anti-helminthic agent, was investigated for hepatocarcinogenesis-promoting potential using a medium-term liver bioassay system for carcinogens. F344 male rats were given a single intraperitoneal injection of diethylnitrosamine (DEN, 200 mg/kg) and then starting 2 weeks later, received praziquantel in the diet at concentrations of 1.5 or 0.5%, or intragastrically at a dose of 1,500 mg/kg once a week for 6 weeks. Control groups received DEN or praziquantel alone. All rats were subjected to two-thirds partial hepatectomy at week 3 and killed at week 8. Development of glutathione S-transferase placental form-positive foci in the liver was significantly increased in terms of both number and area with the 1.5% dose, while only area was affected by the 0.5% dose. The results thus indicate that praziquantel at high dose has promoting potential in rat hepatocytic tumorigenesis.