Desmopressin treatment in nocturia; an analysis of risk factors for hyponatremia.

Aims: To explore the incidence, severity, time course, and risk factors of clinically significant hyponatremia in desmopressin treatment for nocturia. Methods: Data from three multi-center phase 111 trials were pooled. Hyponatremia was categorised as borderline (134-130 mmol/L) or significant (<130 mmol/L). Risk factors were explored with logistic regression and subgroup analysis performed to explore threshold values for contra-indication. Results: In total 632 patients (344 men, 288 women) were analyzed. During dose-titrition, serum sodium concentration below normal range was recorded in 95 patients (15%) and 31 patients (4.9%) experienced significant hyponatremia. The risk increased with age, lower serum sodium concentration at baseline, higher basal 24-hr urine volume per bodyweight and weight gain at time of minimum serum sodium concentration. Age was the best single predictor. Elderly patients (>= 65 years of age) with a baseline serum sodium concentration below normal range were at high risk (75%). Limiting treatment in elderly with normal basal serum sodium concentration to those below 79 years and with a 24-hr urine output below 28 ml/kg would reduce the risk from 8.1% to 3.0% at the cost of 34% fulfilling the contra-indication. Conclusions: The majority of nocturia patients tolerate desmopressin treatment without clinically significant hyponatremia. However, the risk increases with increasing age and decreasing baseline serum sodium concentration. Treatment of nocturia in elderly patients with desmopressin should only be undertaken together with careful monitoring of the scrum sodium concentration. Patients with a baseline serum sodium concentration below normal range should not be treated.