NEW YORK (Reuters Health) – In older men with benign prostatic hyperplasia (BPH) bothered by nocturnal polyuria, a low dose of desmopressin at bedtime can help, according to results of a new study.

Compared with placebo, 0.1 milligrams desmopressin nightly reduced nocturnal diuresis and the number of overnight trips to the bathroom and increased time spent in bed before the first void, the study team reports in January 2011 issue of The Journal of Urology, available online now.

In their report, first author Dr. Chung-Jing Wang from Saint Martin De Porres Hospital, Chiayi, Taiwan, and colleagues note that BPH affects an estimated 40% of men older than 50 years. Nocturia, a common manifestation, harms quality of life and disrupts sleep patterns and nocturnal polyuria is one of the main causes of nocturia.

Although the long-term safety and effectiveness of oral desmopressin has been proven in children with nocturnal enuresis, there remains a lack of long-term safety data on desmopressin in elderly patients and adults with nocturia, the investigators point out.

Therefore, Dr. Wang and colleagues studied 115 men older than age 65 with BPH and nocturia (defined as an average of two or more voids nightly) and nocturnal polyuria (defined as nocturnal urine volume greater than 30% of total daily urine volume). Fifty-seven were randomized to desmopressin (0.1 mg at bedtime) and 58 to matching placebo.

They report that desmopressin significantly decreased nocturnal urine output and the number of nightly voids and prolonged the first sleep period (p < 0.01), compared with placebo. Specifically, 35 of 57 men in the desmopressin arm (61%) had a clinical response, defined as a decrease of two or more nightly voids, compared with 8 of 58 in the placebo arm (14%). Total nocturnal urine volume was 392.1 mL in the desmopressin arm versus 533.1 mL in the placebo arm. Desmopressin also prolonged the duration of sleep before the first void by 30 minutes. Adverse events associated with low dose desmopressin were usually “mild and infrequent,” the investigators report, and comparable with the established safety profile of desmopressin in the treatment of polyuria associated with other conditions. Similar numbers of patients in the desmopressin and placebo arms reported adverse events (29.8% vs 32.8%), mostly headache, dizziness, nausea and asymptomatic hyponatremia. The study team closely monitored serum electrolytes during the study and the serum sodium level in the desmopressin group was always lower than the placebo group. This, they say, suggests that long-term use of the drug in older patients might induce gradual hyponatremia and that serum sodium should be assessed carefully and regularly in all older patients – in their opinion, starting one week after desmopressin initiation and after any dose adjustment. Summing up, Dr. Wang told Reuters Health: “For those elderly with polyuria nocturia with BPH, low dose desmopressin can be used routinely under cautiously monitored the serum electrolytes, (but) it is off label use.”