The
diuretic tolvaptan has been approved for more than 5 years for the indications of euvolemic
hyponatremia due to syndrome of inappropriate
antidiuretic hormone (
SIADH) secretion. In recent years many patients have been treated with
tolvaptan and many physicians could gather practical experience. Other countries, such as the USA had already gained greater experience, also in the indications for hypervolemic
hyponatremia. After approval was granted more than 5000 patients worldwide were included in the so-called
hyponatremia register and 22 active centers in Germany with 317 patients participated. Although some details from this now concluded register have been published, the final publication of the multinational post-authorization safety study on
tolvaptan in the treatment of
SIADH has not yet been published. In the years 2012 and 2013 two warning letters were issued on
tolvaptan. The first letter warned of the risk of a faster increase in serum
sodium using
tolvaptan and provided detailed information on how the risk of osmotic demeyelination can be minimized. So far only one proven case of osmotic demelination syndrome (ODS) is known; however, this occurred following incorrect use of
tolvaptan in a monotherapy. The second warning letter provided information on the potential risk (reversible) of liver damage by
tolvaptan, which resulted from the
TEMPO 3:4 study. In this study
tolvaptan was used in a higher dosage for
therapy of
autosomal dominant polycystic kidney disease. Although the European renal best practice (ERBP) guidelines from 2014 did not recommend
tolvaptan for the indications of
SIADH, other guidelines came to different conclusions. In summary, 5 years after the approval of
tolvaptan there is still no consensus. At the current time many questions still remain unanswered. Initiation of
therapy with
tolvaptan remains reserved for experienced physicians in hospitals. Treatment must be adapted on the basis of a clinical estimation of the individual situation of each patient.