Morris JH, et al. - Pretherapy parameters were hypothesized to predict the rapidity of response to tolvaptan in syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Findings of this study revealed that the rapidity of hyponatremia correction following tolvaptan use in SIADH was predicted by baseline serum sodium and serum urea nitrogen (SUN) values. In those with both low serum sodium and SUN concentrations, caution was recommended when dosing tolvaptan.