ABSENCE OF CHANGES IN ANTIDIURETIC-HORMONE, ANGIOTENSIN-II, AND ATRIAL-NATRIURETIC-PEPTIDE WITH CLOZAPINE TREATMENT OF POLYDIPSIA-HYPONATREMIA - 2 CASE-REPORTS

Background: Polydipsia-hyponatremia is a poorly understood disorder th at causes considerable mortality and morbidity. Hyponatremia in polydi psia-hyponatremia has been attributed to disturbances in antidiuretic hormone (ADH) function. Improvements in polydipsia-hyponatremia during clozapine treatment offered the chance to see if levels of ADH and ot her hormones associated with osmoregulation changed with improvement i n biochemical and clinical measures of polydipsia-hyponatremia. Method : In this preliminary, longitudinal study, we studied 2 male schizophr enic patients (DSM-III-R) who had polydipsia-hyponatremia. Measures we re (1) biochemical and clinical: serum sodium and osmolality, urine os molality and specific gravity, normalized diurnal weight gain, and est imated urine volume and (2) endocrine: ADH, angiotensin II, atrial nat riuretic peptide, and prolactin. Measures were collected during 2 mont hs of baseline (typical neuroleptic) and 6 months of clozapine treatme nt. Results: Single-case statistical procedures showed significant cha nges in sodium levels (a.m. and p.m.), estimated urine volume, and a.m . urine specific gravity in both patients and significantly decreased diurnal weight gain in 1 patient. Both serum and urine osmolality show ed improvement, but values did not reach statistical significance. Low baseline ADH levels persisted through 6 months of clozapine treatment and showed no changes in the context of improvements in serum sodium and osmolality. No significant changes were seen in levels of angioten sin II and atrial natriuretic peptide. Conclusion: Given the limitatio ns of this study, there is some evidence to suggest that the improveme nts in serum sodium and osmolality during clozapine treatment of polyd ipsia-hyponatremia may not be related to serum levels of ADH, although altered ADH receptor function cannot be ruled out. These data need to be extended in larger samples.