Avaliação da dose e efeitos colaterais do tamoxifeno em cadelas hígidas

Abstract

Mammary tumors are the most frequent neoplasms in female dogs. Despite the importance and high incidence of the condition, the strategies employed in animal treatment are limited. Considering how few therapeutic resources are available for canine mammary tumors and the benefits of Tamoxifen in human breast cancer treatment, studies of the value of this drug in veterinary medicine are justified. The aim of this study was to evaluate the side effects of different doses of Tamoxifen in intact and spayed female dogs. Tamoxifen was administered for 120 days at 0.5 and 0.8mg/Kg/day and the effects were assessed every ten days through clinical examination, hemograms and serum biochemistry, and by ophthalmological examination and myelograms before, during and after the completion of treatment. The uterus was examined histopathologically after ovariohysterectomy. The side effects of Tamoxifen in female dogs were similar to those observed in women treated for breast cancer. The ophthalmological side effects were reversible after suspension or termination of treatment and are also compatible with the patients quality of life. The uterine lesions observed in histopathological examination, such as cystic endometrial hyperplasia-pyometra, metaplasia and endometrial polyps, can be prevented by elective ovariohysterectomy before Tamoxifen treatment, suggesting that only spayed animals should be given this medication. The slight alterations observed in biochemistry, hemograms and myelograms in this study are more associated with individual variationsthan with the side effects of Tamoxifen. It is suggested that the higher dose (0.8 mg/Kg/day) be used to achieve better chances of therapeutic success in treating canine mammary tumors, since the side effects can be correctly assessed and controlled individually.