INVOLVEMENT OF THE ALPHA(2)-ADRENERGIC SYSTEM IN POLYDIPSIA IN SCHIZOPHRENIC-PATIENTS - A PILOT-STUDY

Animal studies have suggested the involvement of the adrenergic system in drinking behavior. The present study investigated the involvement of the alpha(2)-adrenergic system in the polydipsia of patients with c hronic schizophrenia by use of an alpha(2) agonist and an antagonist. Four patients with schizophrenic disorders accompanied by intermittent hyponatremia and polydipsia were the subjects of, and completed, this study. Drinking behavior was assessed by calculating the percent of m aximum weight gain [PMWG: (maximum diurnal weight - standard weight) x 100/standard weight]. Standard weight was defined as body weight afte r 8 h of water restriction. Clonidine (75, 150, and 225 mg/day) increa sed the PMWG in a dose-dependent manner in the four subjects. In contr ast, in three of the subjects, mianserin (30, 60, and 90 mg/day) decre ased PMWG, and tile severe polydipsia disappeared almost completely Th ese findings indicate clearly that the alpha(2)-adrenergic system is i nvolved in the drinking behavior of schizophrenic patients. Mianserin appears to be clinically useful in treating such patients with polydip sia.