Contraceptive efficacy of tamoxifen in female hamsters

Systemic administration of tamoxifen (trans-1-(4-B-dimethylaminoethoxyphenyl)-1,2-diphenyl-but-1-ene), an antiestrogen, at a dose level of 2 mg/kg body weight on days 1, 2 and 3 post-coitum (p.c.) intercepts pregnancy during the peri-implantation period in 70-80% of hamsters. Significant alterations in the circulating levels of estradiol and progesterone were accompanied by the abolition of peak activities of various uterine lysosomal enzymes in the treated animals. The present study, therefore, suggests that estrogen plays a crucial role during the process of ovum-implantation in hamsters, and tamoxifen displays an interceptive role in this species.