Exp Clin Endocrinol Diabetes 2013; 121 - P45
DOI: 10.1055/s-0033-1336718

A 51-year old patient with SIADH and hyperkalemia under chronic and high-dose treatment with tolvaptan

S Schneider 1, A Schäffler 1
  • 1University Hospital Regensburg, Department of Internal Medicine I, Regensburg, Germany

In September 2011, a 50-year old male patient was hospitalized due to weakness and dizziness. Serum sodium was 107 mmol/l; a SIADH was diagnosed. The medical history showed an oral squamous cell carcinoma treated with surgery, chemotherapy and radiation in 2006. A CT-scan indicated no recurrence of the tumor. Furthermore, the patient took antidepressant drugs, which were discontinued, and a chronic obstructive pulmonary disease GOLD IV – probably related to smoking – was diagnosed. Both – antidepressant therapy and COPD – are possible reasons for SIADH. However, cancer- and radiation-induced SIADH was diagnosed during the further disease course. Serum sodium levels increased under fluid restriction and the symptoms improved. The patient was discharged without any further therapy.

As the patient could not handle fluid restriction because of sicca symptoms due to radiation, he was hospitalized twice again with symptomatic hyponatremia. In February 2012, a treatment with oral tolvaptan was started with 15 mg qd.

In April 2012, serum potassium levels increased for the first time. Tolvaptan was reduced (15 mg twice a week) and a therapy with torasemid 5 mg qd was started. After one week serum sodium decreased (118 mmol/l) and the patient was hospitalized again. The tolvaptan dosage was elevated (15 mg qd), torasemid was continued und we began a therapy with the ion exchanger Resonium® what contributed to normalizied serum sodium and potassium levels.

In the meantime the patient was hospitalized again four times with hyponatremia (and hyperkalemia), probably due to exacerbation of COPD and an uncontrolled fluid uptake. In November 2012, the dosages of tolvaptan (45 mg qd), Resonium® and torasemid have been increased. Under this therapy, no further disturbance of electolyt homeostasis occurred.

Chronic high dose tolvaptan treatment is safe and effective and the rarely occuring hyperkalemia can be controlled by a combination of loop diuretics and ion exchangers.