Treatment of Psychogenic Polydipsia: Comparison of Risperidone and Olanzapine, and the Effects of an Adjunctive Angiotensin-II Receptor Blocking Drug (Irbesartan)

Abstract

Objective: Our objective was to determine the outcome of novel strategies in 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 symptoms, had been hospitalized for the previous 10 years because of severe polydipsic behaviour complicated by water intoxication. Treatment: Novel antipsychotic agents, risperidone and olanzapine, as well as the specific angiotensin-II receptor blocking drug, irbesartan were employed at selected intervals in a study lasting nearly 3 years. A strict behavioural management programme was ongoing, in which diurnal weight change and the number of breaches of weight limits, requiring management in a low-stimulus environment, were documented on a daily basis. Summary measures of diurnal weight change and behavioural intervention were charted against changes in treatment. Outcome: Polydipsic behaviour improved on risperidone up to 4 mg daily, but was not sustained. Olanzapine was similarly successful in stabilizing polydipsia, and improvement was achieved with the addition of irbesartan. Conclusion: We suggest that the D2-sparing profiles of receptor binding achieved with low-dose risperidone and olanzapine may account for this beneficial effect. The benefit derived with irbesartan implicates the involvement of brain angiotensin systems centrally in helping to regulate drinking behaviour.