Background Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is one of the most frequent causes of hyponatraemia. Conventional treatments do not act on the vasopressin V2 receptor, are limited and with variable efficiency. Tolvaptan is the first selective vasopressin V2 receptor antagonist, administered orally and suitable for the treatment of hyponatraemia associated with SIADH.

Purpose To study the characteristics of patients treated with tolvaptan, analysing the causes of hyponatraemia, their analytical situation and their home treatments involved in the decrease in the sodium concentration.

Material and methods A descriptive and retrospective study of patients treated with tolvaptan since 2014. Data were obtained from medical records. The suitability of the treatments was established based on RUNKLE, Isabelle et al. treatment algorithms and home treatments’ possibility of causing hyponatremia as an adverse effect was reviewed.

Results Twenty-two patients (13 male and nine femalefemales) with a mean age of 73 years were treated with tolvaptan. Possible causes of hyponatraemia were: cerebrovascular 5/22; secondary to psychiatric treatment 6/22; cirrhosis 1/22; oncological pathology 3/22; multifactorial 5/22; and undefined 2/22. Blood tests showed that 5/22 patients had severe-moderate hyponatraemia and 17/22 mild-moderate hyponatraemia. Subsequently, the Furst Formula was calculated and patients were classified accordingly in order to evaluate the suitability of the treatments for sodium value correction. In all cases, the proposed algorithms were followed, obtaining normal values of sodium after the use of tolvaptan.

When reviewing pre-admission treatments, 10/22 patients were being treated with one or more drugs that could produce hyponatraemia (cisplatin, valproic acid, hydrochlorothiazide, duloxetine, mirtazapine and/or sertraline).

Conclusion The use of tolvaptan allowed the obtainment of plasma concentrations of sodium within normal ranges. However, it is important to know the factors that can trigger the SIADH as well as to handle the correct treatment algorithms. On the other hand, it is important to emphasise the adverse effects of the drugs in patients who are admitted to a hospital.

Reference and/or Acknowledgements 1. Runkle, Isabelle, et al. Tratamiento de la hiponatremia secundaria al síndrome de secreción inadecuada de la hormona antidiurética: Algoritmo multidisciplinar. Nefrología (Madrid)2014;34(4):439–450.

No conflict of interest