Background Tolvaptan is the first oral antagonist of the vasopressin V2 receptor. It is indicated in adult patients with hyponatraemia secondary to syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH).

Purpose To evaluate the use of tolvaptan in a tertiary hospital.

Materials and Methods An observational study was conducted on patients treated with tolvaptan from January 2012 to September 2012. Data was collected from the review of medical histories, lab tests and dispensing records. A data collection sheet was designed on which were recorded: diagnosis related to hyponatraemia, age, gender, dose, clinical department that prescribed it, serum sodium when the treatment with tolvaptan was initiated, evolution and possible side effects.

Results 6 patients (50% male) received tolvaptan in the study period. Average age was 72.53 years. The clinical department that wrote the prescription was Internal Medicine in five cases and Oncology in the other one. The background pathology was lung cancer in two cases, heart failure in two cases, idiopathic SIADH in one case and only one case of SIADH. The average serum sodium concentration pre-treatment was 113 (101–120) mg/dl. The dose usually used was 15 mg/day, although one patient took 30 mg/day. The average length of treatment was 123 (30–270) days. Only one patient discontinued treatment due to gastrointestinal side effects. One terminal cancer patient and an 85-year-old patient died. The average cost-day per patient was €65.75.

Conclusions Our results agree with the tolvaptan clinical trials, that it appears to be safe and effective in the treatment of hyponatraemia refractory to other treatments. The high cost of the treatment and the limited experience in its use required strict control over its administration.

No conflict of interest.