There have also been reports of a reduction in nocturnal polyuria in elderly subjects treated with low doses of desmopressin. However, the data are limited and difficult to interpret due to low patient numbers in the open design studies and use of intranasal desmopressin in 2 studies. This RCT explored the long-term efficacy and safety of low dose oral desmopressin in 115 elderly patients with benign prostatic hyperplasia (BPH) with nocturnal voids more than 2 times and nocturnal polyuria greater than 30% of total daily urine volume.
The patients, who were aged >65 years and had an International Prostate Symptom Score (IPSS) of ≥14, were randomised to received placebo (n= 58) or 0.1 mg desmopressin (n= 57) orally at bedtime. They completed flow volume charts and recorded voiding data in diaries throughout the study. Assessments were carried out at an outpatient clinic from the first visit, and after 1, 3, 6 and 12 months of treatment, and included urinalysis, urine sodium, urine osmolality, serum electrolytes, prostate specific antigen, IPSS, quality of life, transrectal ultrasonography of prostate, uroflowmetry and post-void residual urine volume.
The following findings were reported:
• A clinical response (decrease of 2 or more voids per night) was achieved by 35 (61.40%) patients on desmopressin and by 8 (13.80%) on placebo (p < 0.001).
• Compared with placebo, the odds of achieving a clinical response were 4.5 times greater for patients receiving desmopressin (95% CI, 4.0 to 105.2).
• Total nocturnal urine volume was 392.1 ml in the desmopressin group and 533.1 ml in the placebo group.
• Mean first sleeping period was 120 minutes longer in the desmopressin group than in the placebo group (101.6 minutes).
• The quality of life index increase was greater than 2 in 54 (97.70%) patients in the desmopressin group vs. 8 (13.8%) in the placebo group.
• Similar numbers of patients reported adverse events, with 17 (29.8%) in the desmopressin group and 19 (32.8%) in the placebo group.
• One patient experienced consciousness disturbance due to hyponatremia and withdrew from the study.
• Asymptomatic hyponatremia occurred in 10 patients in the placebo group and in 9 in the desmopressin group.
• There was no difference between the groups with regard to serum chloride, potassium, urine sodium, urine osmolality, IPSS, peak flow rate, prostate volume and PSA.
The researchers conclude from these findings that low dose oral desmopressin reduced nocturnal diuresis and the number of nocturnal voids, and increased the time from bedtime to the first nocturnal void in patients with benign prostatic hyperplasia. They note that as long-term desmopressin therapy gradually decreases serum sodium, it might induce hyponatremia, even in patients without initial hyponatremia, therefore serum sodium should be assessed carefully, at least at 1 week after treatment.