Tamoxifen-induced acute mania: A case report

Introduction Tamoxifen is widely used for the treatment of hormone-responsive breast cancer, osteoporosis, and post-menopausal symptoms. Also, tamoxifen is currently under investigation for its anti-manic properties. In this article, we report a case who developed manic episode following the initiation of tamoxifen and remitted with discontinuation of the medication. Case Report A 58-year-old woman was diagnosed with breast cancer. Pathologic diagnosis was invasive ductal carcinoma. Following bilateral total mastectomy operation, trastuzumab was initiated with intervals of 21 days. Five days before the fourth application of trastuzumab, tamoxifen was added. On the sixth day following the initiation of tamoxifen, manic symptoms were developed and she was diagnosed as acute mania. Management and Outcome The oncology department suggested withdrawing tamoxifen due to a possible association between tamoxifen initiation and behavioral symptoms. Manic symptoms were rapidly (approximately 24 h) improved following cessation of tamoxifen. Psychiatric evaluation on the fifth day following cessation of tamoxifen revealed no manic symptoms. An aromatase inhibitor-exemestane was initiated and she showed no side effects with this medication since then. Discussion To our knowledge, this is the first case report of probable tamoxifen-induced mania. Our case report at least indicates that there were possibly some patients who were sensitive to the tamoxifen’s nervous system effects, mainly to manic effects. In conclusion, clinicians should be aware of these rare behavioral adverse effects of tamoxifen.