Severe Hyponatremia During First Cycle of Cyclophosphamide/Doxorubicin Chemotherapy

Syndrome of inappropriate anti-diuretic hormone release (SIDAH) is a condition characterized by an unregulated release of anti-diuretic hormone (ADH) resulting in increased water retention and decreased plasma osmolarity. Without regulation, ADH release will cause a significant decrease in plasma sodium concentration and can present with cramping, nausea, vomiting, and in severe cases, seizures, and potentially falling into a comatose state. The causes of SIADH are variable and range from infections, some malignancies to some medications. We report a rare case of SIADH resulting from a single cycle of doxorubicin and cyclophosphamide chemotherapy in a 66-year-old female with left and right, estrogen receptor positive breast cancer who experienced seizures resulting from a dramatic drop in sodium levels.