Evaluation of adverse effects in tamoxifen exposed healthy female dogs

Mammary tumors are among the most frequent neoplasms in female dogs, but the strategies employed in animal treatment are limited. In human medicine, hormone manipulation is used in cancer therapy. Tamoxifen citrate is a selective inhibitor of oestrogen receptors and exerts a potent anti-oestrogen ef...

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Bibliographic Details
Published in:	Acta veterinaria scandinavica Vol. 52; no. 1; p. 67
Main Authors:	Tavares, Wanessa L F, Lavalle, Gleidice E, Figueiredo, Mariana S, Souza, Aline G, Bertagnolli, Angelica C, Viana, Fernando A B, Paes, Paulo R O, Carneiro, Rubens A, Cavalcanti, Guilherme A O, Melo, Marilia M, Cassali, Geovanni D
Format:	Journal Article
Language:	English
Published:	England BioMed Central 22-12-2010 BioMed Central Ltd BMC
Subjects:	Animals Antineoplastic Agents, Hormonal - administration & dosage Antineoplastic Agents, Hormonal - adverse effects Biochemistry Breast cancer Cancer therapies Dog Diseases - chemically induced Dogs Dose-Response Relationship, Drug Edema - chemically induced Edema - veterinary Female Females Hysterectomy - veterinary Medicine Pathology Postoperative period Pyometra - chemically induced Pyometra - veterinary Retinitis - chemically induced Retinitis - veterinary Tamoxifen - administration & dosage Tamoxifen - adverse effects Teaching hospitals Tumors Veterinary colleges Veterinary medicine Vulvar Diseases - chemically induced Vulvar Diseases - veterinary Womens health
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Summary:	Mammary tumors are among the most frequent neoplasms in female dogs, but the strategies employed in animal treatment are limited. In human medicine, hormone manipulation is used in cancer therapy. Tamoxifen citrate is a selective inhibitor of oestrogen receptors and exerts a potent anti-oestrogen effect on the mammary gland. The aim of this study was to evaluate the adverse effects when exposing healthy female dogs to tamoxifen. Tamoxifen was administered for 120 days at a dose of 0.5 or 0.8 mg/kg/day to either intact or spayed female dogs. The effects were assessed through clinical examination, haematology, serum biochemistry, ophthalmology and bone marrow aspirate examination. Ovariohysterectomy was performed and the uterus examined by histopathology. Vulva oedema and purulent vaginal discharge developed with 10 days of tamoxifen exposure in all groups. Pyometra was diagnosed after around 90 days of exposure in intact females with frequencies increasing during the following 30 days of exposure. Up to 50% of dogs within the groups developed retinitis but none of the dogs had signs of reduced visual acuity. The prevalence of retinitis in each group was similar after 120 days of exposure. Haematological, biochemical and bone marrow changes were not observed. Due to the high risk of developing pyometra after prolonged exposure to tamoxifen, only spayed animals should be given this medication. A dose of 0.8 mg tamoxifen/kg body weight/day is recommended when treating tamoxifen-responsive canine mammary tumors. Due to the high risk of developing pyometra, ovariohysterectomy is recommended.
ISSN:	1751-0147 0044-605X 1751-0147
DOI:	10.1186/1751-0147-52-67