SUN-027 Efficacy of Pharmacokinetic and Physiological Assessment of DDAVP Tablet in Treating Diabetes Insipidus of Chordoid Glioma

Abstract Disclosure: M. Iwabuchi: None. Background: Chordoid glioma is a rare low-grade tumor that arises from the anterior wall or roof of the third ventricle. Gross total resection is the ideal treatment, although tumor size and location often impede radical resection. The risk of surgical morbidity cannot be ignored. Therefore, incompletely resected tumors will continue to grow slowly and may require later resection. Diabetes insipidus (DI) is one of complications and desmopressin acetate hydrate (DDAVP) tablets are a synthetic analogue of the natural pituitary hormone, 8-arginine vasopressin, an antidiuretic hormone affecting renal water conservation. In 2021, Goswami and coauthors reported that seasonal rhythms of vasopressin release and aquaporin-2 excretion assure appropriate water conservation, and plasma AVP levels are nearly double in the warmer season compared with the colder season and these seasonal fluctuations correlate with parallel modulation in AQP2 excretion. CLINICAL CASE: A 34-year-old woman underwent resection of chordoid glioma of third ventricle in 2011. However, MRI revealed tumor regrowth in the hypothalamic region in 2015 and 2023. Therefore, each time a new tumor recurred, resection and 50 Gy radiation therapy were performed. Post-operatively, she evolved with DI. At this time, her plasma had 153 mEq/L of sodium and 311 mOsm/kg H2O of osmolality. She started to take DDAVP tablets, and the dose of the tablets increased gradually up to 480 microgram per day. Rittig and coauthors reported the effect of food intake on the pharmacokinetics and antidiuretic activity of oral desmopressin in hydrated normal subjects. The total absorption of oral desmopressin was significantly higher when taken during the fasting state compared with its administration with or 1.5 hours after a standard meal. Her prescription of DDAVP tablet was changed to take the tablets before meals and bedtime. This change produced improvement of her general condition, plasma sodium concentration to 140 mEq/L and osmolality to 281 mOsm/kg H2O respectively. Appropriate timing of oral administration was adjusted to increase the absorption efficiency of DDAVP, while the dose of DDAVP was adjusted considering physiological seasonal rhythms. DDAVP oral doses of 480 micrograms in summer and 240 micrograms in winter were sufficient to maintain normal serum osmolarity. Naturally, minor adjustments were made considering her physical condition. CLINICAL LESSON: Treatment aligned with the seasonal rhythms of vasopressin release and aquaporin-2 excretion assures adequate water conservation in humans. The physiological seasonal rhythm of vasopressin and the bioavailability of DDAVP oral tablets should be considered in the treatment of diabetes insipidus. This is the first report demonstrating the efficacy of pharmacokinetic and physiological assessment of DDAVP tablet in treating diabetes insipidus complicated with chordoid glioma. Presentation: Sunday, July 13, 2025