The relationship between the action of arginine vasopressin and responsiveness to oral desmopressin in older men: A pilot study

OBJECTIVES: To identify whether oral desmopressin (ddAVP) reduced nocturnal urine volume (NUV) in older men with nocturia without obvious bladder outlet obstruction and to determine whether deficiencies in arginine vasopressin (AVP) release and action demonstrated using water deprivation testing predicted responsiveness to ddAVP. DESIGN: Participants had a 2-day Clinical Research Center (CRC) evaluation followed by a double-blinded, placebo-controlled, crossover trial of individually titrated oral ddAVP. SETTING: Participants were from a single Department of Veterans Affairs Medical Center. MEASUREMENTS: Maximum urine osmolality and percentage increase in osmolality were measured after subjects received aqueous vasopressin as part of the overnight water deprivation study; these data were used to categorize participants as normal, having partial central AVP deficiency, or having impaired renal responsiveness to AVP. Response to ddAVP was assessed using data from frequency-volume records. RESULTS: Fourteen participants completed the CRC stay and ddAVP trial. Subjects given ddAVP reduced NUV significantly from baseline (P=.02) and had significantly lower NUV than when on placebo (P=.01). The mean net reduction in NUV from ddAVP compared to placebo was 14±18%. Using water deprivation testing to categorize participants, 10 were normal, two had partial central AVP deficiency, and two had impaired renal responsiveness. The mean net reduction in NUV for those with abnormal water deprivation tests was 11±25%, versus 15±16% for those with normal water deprivation testing (P=.70). CONCLUSION: In this small randomized, controlled trial in older men with nocturia, ddAVP reduced NUV. Counter to expectations, participants deemed normal according to water deprivation tests had approximately equivalent responsiveness to ddAVP. Although this study cannot offer definitive conclusions on the lack of prediction of water deprivation testing for ddAVP benefit, these data offer additional information that may help clarify the pathophysiology and optimal treatment of nocturia in older men.