• Joseph G Verbalis, Howard Ellison, Mary Hobart, Holly Krasa, John Ouyang, Frank S Czerwiec, and Investigation of the Neurocognitive Impact of Sodium Improvement in Geriatric Hyponatremia: Efficacy and Safety of Tolvaptan (INSIGHT) Investigators.
• Division of Endocrinology and Metabolism, Georgetown University, Washington, DC. Electronic address: verbalis@georgetown.edu.
• Am. J. Kidney Dis. 2016 Jun 1; 67 (6): 893-901.

BackgroundThis trial assessed the effect of tolvaptan on cognition, gait, and postural stability in adult patients with mild to moderate asymptomatic hyponatremia.Study DesignPhase 3b, multicenter, randomized, double-blind, placebo-controlled, parallel-group pilot study.Setting & Participants57 men and women 50 years or older with chronic asymptomatic euvolemic or hypervolemic hyponatremia (serum sodium concentration >120-<135 mEq/L) at 16 sites.InterventionPatients were randomly assigned 1:1 to receive tolvaptan or matching placebo beginning at a dose of 15mg/d, with titration to 30 or 60mg/d based on change in serum sodium concentration and tolerance.OutcomesPrimary: change from baseline in the neurocognitive composite score of speed domains. Secondary: changes from baseline in individual neurocognitive domain scores, overall neurocognitive composite score, gait and postural stability test results, and serum sodium concentrations.ResultsMean serum sodium concentration increased from 129 to 136 mEq/L in the tolvaptan group and from 130 to 132 mEq/L in the placebo group (P<0.001). There was no difference in overall neurocognitive composite scores of speed domains between groups, except for the psychomotor speed domain, which was statistically improved following hyponatremia correction with tolvaptan (treatment effect, 0.27; 95% CI, 0.04-0.51; P=0.03).LimitationsThere were some imbalances between treatment groups in baseline neurocognitive function scores and some baseline test results were near normal, leaving little opportunity for improvement. Formal sample size calculations were not performed because this was a pilot study. The study population was small (n=57) and treatment was of short duration (3 weeks). The primary end point of the study was not significant; thus, subgroup analyses are subject to errors of multiplicity and should be regarded as hypothesis generating.ConclusionsTolvaptan was effective in reversing chronic hyponatremia, and this correlated with improvements in results of a variety of neurocognition tests, particularly rapid motor movements, which tended to reverse following return to a low baseline serum sodium concentration after treatment withdrawal.Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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