The Effects of Long-Term Administration of Oral Desmopressin on the Baseline Secretion of Antidiuretic Hormone and Serum Sodium Concentration for the Treatment of Nocturia: A Circadian Study

Purpose: We assessed the effects of long-term oral desmopressin on serum sodium and baseline antidiuretic hormone secretion in elderly patients with nocturia. Materials and Methods: A total of 15 elderly male patients with severe nocturia (greater than 3 voids nightly) who did not show hyponatremia within 7 days of administration of 0.2 mg desmopressin were enrolled in this study. Desmopressin (0.2 mg) was administered orally nightly for 1 year. Before and 1 month after the 1-year medication 24-hour circadian studies were performed to monitor changes in antidiuretic hormone. Every 3 months during the 1-year medication serum changes and timed urine chemistry were monitored. Results: Desmopressin significantly decreased nocturnal urine output and the number of nocturia episodes (p <0.01). Compared to before treatment desmopressin gradually decreased serum sodium and induced statistically but not clinically significant hyponatremia after 6 months of treatment. After discontinuing desmopressin serum sodium returned to the normal range in all patients. There were no significant differences when baseline and posttreatment endogenous antidiuretic hormone were compared. No serious systemic complications were found during medication. Conclusions: Long-term desmopressin administration gradually decreased the serum concentration and induced significant hyponatremia from 6 months in patients who did not show initial hyponatremia. Long-term administration of desmopressin for 1 year in elderly patients did not affect baseline antidiuretic hormone secretion. For long-term desmopressin administration serum sodium should be assessed regularly, at least every 6 months.