Selection of AVP-Shortage Patients as Candidates for Low-Dose Oral Desmopressin Administration

OBJECTIVE: We herein attempted to select male patients with an elevated nocturnal urinary frequency possibly due to a shortage of AVP. These patients may be good candidates for low-dose oral desmopressin administration. PATIENTS AND METHODS: Serum and spot urine osmolality, electrolytes, serum creatinine, casual blood glucose, plasma brain natriuretic polypeptide (BNP), and plasma AVP were measured at the same time in 97 elderly male patients with urinary symptoms under free water drinking. RESULTS: A binary plot of plasma AVP and serum osmolality indicated a region at which patients had relatively lower AVP considering higher serum osmolality. It was tentatively named the desmopressin region. Twenty out of 97 (20.6%) patients were in the desmopressin region. Daily urine output did not exceed 3 L in any patient. Urine osmolality was slightly lower in patients in the desmopressin region. No significant differences were observed in urine volume, urinary frequency, or urination questionnaire scores between both groups. CONCLUSION: AVP-shortage patients may be selected for treatment with oral desmopressin based on measurements of serum osmolality and plasma AVP.