Treatment of psychogenic polydipsia: comparison of risperidone and olanzapine, and the effects of an adjunctive angiotensin-II receptor blocking drug(irbesartan)

Objective: Our objective was to determine the outcome of novel strategies i n managing a case of severe polydipsia. Clinical picture: The patient was a 39-year-old male with a 20-year history of paranoid schizophrenia who, despite only mild residual psychotic sympto ms, had been hospitalized for the previous 10 years because of severe polyd ipsic behaviour complicated by water intoxication. Treatment: Novel antipsychotic agents, risperidone and olanzapine, as well as the specific angiotensin-II receptor blocking drug, irbesartan were empl oyed at selected intervals in a study lasting nearly 3 years. A strict beha vioural management programme was ongoing, in which diurnal weight change an d the number of breaches of weight limits, requiring management in a low-st imulus environment, were documented on a daily basis. Summary measures of d iurnal weight change and behavioural intervention were charted against chan ges in treatment. Outcome: Polydipsic behaviour improved on risperidone up to 4 mg daily, but was not sustained. Olanzapine was similarly successful in stabilizing poly dipsia, and improvement was achieved with the addition of irbesartan. Conclusion: We suggest that the D2-sparing profiles of receptor binding ach ieved with low-dose risperidone and olanzapine may account for this benefic ial effect. The benefit derived with irbesartan implicates the involvement of brain angiotensin systems centrally in helping to regulate drinking beha viour.