INVOLVEMENT OF THE ENDOGENOUS OPIOID SYSTEM IN THE DRINKING BEHAVIOR OF SCHIZOPHRENIC-PATIENTS DISPLAYING SELF-INDUCED WATER-INTOXICATION -A DOUBLE-BLIND CONTROLLED-STUDY WITH NALOXONE

Previously we found significant suppression of polydipsia in a schizop hrenic patient with PIP syndrome (psychosis, intermittent hyponatremia , and polydipsia). Suppression was obtained with a small dose of nalox one injected once every 2 weeks in long-term repeated studies, We atte mpted to confirm the effect of naloxone on PIP syndrome by using a dou ble-blind controlled study. The body weights of eight schizophrenic in patients with PIP syndrome were checked five times daily, and the maxi mum weight gain during 1 day was chosen as an index of their polydipsi a. Naloxone (0.6 mg in three divided doses) or placebo (saline) inject ion was given once every 2 weeks three times. Assignment to either the naloxone or placebo series was done randomly in a double-blind, cross over design. Naloxone decreased the maximum weight gain per day signif icantly in five cases. However, naloxone also increased weight gain si gnificantly in three cases, There was no correlation of the weight-inc reasing effect of naloxone with the duration and intensity of excessiv e drinking, Our findings showed that the endogenous opioid system migh t be related to compulsive drinking behavior in the PIP syndrome and t hat opioid antagonists such as naloxone or naltrexone could be useful in the therapy of PIP syndrome.