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 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.