Endocrine Abstracts

Vasopressin receptor 2 antagonist (V2RA) provide treatment option for patients with hyponatraeamia in the context of syndrome of inappropriate antidiuretic hormone secretion (SIADH).

We report the results of seven patients (six males, one female, average age 65.7) with hyponatraemia secondary to SIADH treated with V2RA (Tolvaptan) in years 2011–2013. Six patients had underlying diagnosis of lung cancer, one patient was diagnosed with sarcoidosis. Four patients died due to their underlying disease, three patients remain under the continuing follow-up.

To exclude other causes of hyponatraemia we checked, thyroid function, plasma, and urine osmolalities, urinary sodium, cortisol level, and performed short synacthen test. The initial treatment was fluid restriction. Three patients (42.86%) were transiently treated with demeclocycline, subsequently switched to V2RA. V2RA doses varied with total weekly doses between 35 and 75 mg.

The average sodium concentration before commencing V2RA treatment, was 121.74±5.09 mmol/l (range 112–126 mmol/l). The average correction time of hyponatraemia was 9.28 days. The sodium levels were corrected on average by 14.86±6.41 mmol/l. The average rate of correction was 4.1 mmol/day (range 0.44–11 mmol/day).

Patients were followed for average of 237.8 days. Total time of follow-up was 1665 patient-days. Patients’ renal function and electrolytes were monitored. We obtained following results, pre- and post-V2RA use: creatinine 82.67 vs 83.67 umol/l (+1.21%), urea 5.13 vs 7.23 mmol/l (+40.9%), potassium 4.45 vs 4.08 mmol/l (−8.24%). Monitoring of liver function tests (LFTs) revealed following pre- and post-V2RA average levels of aspartate transaminase 44.8 vs 43.2 IU/l (−3.7%), alanine transaminase 31.5 vs 32.3 IU/l (+2.65%) and total bilirubin 16.3 vs 14.0 umol/l (−14.29%) respectively.

Our case series gives evidence for effective use of V2RA in the treatment of hyponatraemia in context of SIADH without excessively rapid hyponatraemia correction or significant changes in levels of creatinine, potassium, and LFTs.