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Severe hyponatraemia in two patients with breast cancer caused by low-dose cyclophosphamide and precipitated by aprepitant
  1. Shefali Parikh,
  2. Laura Pettit and
  3. Huzeifa AbdelGadir
  1. Oncology, Royal Shrewsbury Hospitals NHS Trust, Shrewsbury, UK
  1. Correspondence to Dr Shefali Parikh; shefalipp90{at}


Two postmenopausal women with breast cancer developed acute confusion and seizures, less than 24 hours after the first cycle of neoadjuvant chemotherapy with fluorouracil, epirubicin and low-dose cyclophosphamide. They were found to have severe, life-threatening hyponatraemia with sodium levels of 113 and 115 mEq/L, respectively. Both women made a full recovery within 24 hours of admission with slow correction of sodium levels. Following investigational workup, the most likely diagnosis was cyclophosphamide-associated syndrome of inappropriate antidiuretic hormone secretion (SIADH). Aprepitant - a commonly used antiemetic and moderate cytochromeP450 3A4 inhibitor was identified as the precipitating factor. Aprepitant was discontinued and both women were successfully re-challenged with full dose cyclophosphamide in an outpatient setting with no subsequent adverse events. This is a typical case of a rare cause of a common medical problem. A systematic approach to diagnosis and treatment of hyponatraemia in an oncology patient requires awareness of toxicities of systemic anticancer agents.

  • Breast cancer
  • Chemotherapy
  • Drug interactions

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  • Contributors HA and LP were responsible for the conception of the work. Data collection and drafting of the initial manuscript was completed by SP. Critical revision of the manuscript and final approval of the version to be published were completed by SP, LP and HA.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.