Intravenous conivaptan for the treatment of hyponatraemia caused by the syndrome of inappropriate secretion of antidiuretic hormone in hospitalized patients: a single-centre experience.

BACKGROUND Intravenous conivaptan is a novel therapeutic agent indicated for the treatment of euvolaemic and hypervolaemic hyponatraemia. However, there is paucity of reported clinical experience using conivaptan for the treatment of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Moreover, while there is reasonable concern for overcorrection, no pre-treatment variables are known to be helpful to identify patients at risk for rapid correction. METHODS We searched our records for hospitalized patients treated with intravenous conivaptan for moderate to severe hyponatraemia due to SIADH, with a starting serum sodium <130 mmol/L, between 2006 and 2009 (n = 18), to examine its efficacy as aquaretic, and to search for pre-treatment variables that could predict degree of response. RESULTS Twenty-four hours after initiation of therapy, all patients had at least a 3-mmol/L increase in serum sodium, with 66.7% (12/18) of the patients having an absolute increase >or=4 mmol/L, and a median increase in serum sodium of 7 mmol/L (range: 3-16 mmol/L). Concomitantly, urine osmolality decreased in all patients with a mean reduction of 45.9 +/- 28.8% from baseline. Lower serum sodium, lower blood urea nitrogen and higher estimated glomerular filtration rate at baseline had a significant correlation with the magnitude of the absolute increase in serum sodium 24 hours after initiation of therapy. CONCLUSIONS We conclude that intravenous conivaptan is an effective aquaretic to treat hyponatraemia caused by SIADH, as evidenced by a simultaneous increase in serum sodium and decrease in urine osmolality. Baseline values of serum sodium, blood urea nitrogen and estimated glomerular filtration rate may help predicting the magnitude of response to therapy.