Effect of papain on different phases of prenatal ontogenesis in rats

The present investigations were performed to re-examine the findings of previous studies conducted in the sixties and seventies, in which oral or intraperitoneal administration of various formulations of the papaya plant (Carica papaya L.) during different phases of pregnancy was reported to have exerted a number of effects on pregnancy and embryonic development, such as antiimplantation activity, increased postimplantation loss, and embryotoxicity. In two independent experiments, a well-defined and standardized papain was administered orally to Wistar rats in doses up to 800 mg/kg during blastogenesis (days 0 to 6 of gestation, study 2) or embryogenesis (days 6 to 15 of gestation, study 1). When administered during blastogenesis, the preimplantation loss index was significantly decreased and the number of fetuses was significantly increased in the treated rats. No dead fetuses were found in any test group, and no treatment-related increase in postimplantation loss was seen in either study. External, skeletal, and visceral examinations of fetuses did not reveal any important findings. The results of the present investigations lead to the clear conclusion that oral administration of papain up to a dose of 800 mg/kg does not adversely affect prenatal development and does not cause signs of maternal toxicity.