Pharmacological treatments for psychosis-related polydipsia

Polydipsia is the intake of more than three litres of fluids per day. Primary polydipsia occurs when excessive drinking cannot be explained by an identified medical condition, and is not secondary to polyuria. The prevalence of this problem in psychiatric inpatients has been estimated at between 6 and 17%. It can hinder standard care and be a highly disabling, even life-threatening condition.

To review the effect of pharmacological interventions for the treatment of psychosis-related polydipsia.

The reviewers searched the Cochrane Schizophrenia Group's Register (January 2002) which is compiled by up-to-date methodical searches of BIOSIS, The Cochrane Library, CINAHL, Dissertation abstracts, EMBASE, LILACS, MEDLINE, PSYNDEX, PsycINFO, RUSSMED and Sociofile and is supplemented with hand searching of relevant journals and numerous conference proceedings. References of all identified studies were also searched for further trials.

All randomised controlled trials involving people with a psychotic illness and secondary polydipsia, which evaluated drug treatments, and measured clinically meaningful outcomes.

Reviewers, working independently, inspected citations, ordered papers, and then re-inspected and quality assessed the studies. They also worked independently to extract data. For homogeneous dichotomous data, the relative risk (RR), 95% confidence interval (CI), and, where appropriate, the number needed to treat (NNT) and the number needed to harm (NNH), were calculated on an intention-to-treat basis. Reviewers assumed that people who left the study early or were lost to follow-up had no improvement. Weighted mean differences (WMD) were calculated for continuous data. Data was excluded if loss to follow-up was greater than 50%.

The reviewers identified two trials which fulfilled the inclusion criteria, (total n=17, duration 3-6 weeks). Few data were reported and, because of inappropriate use of crossover methodology, it could not all be used in this review. For the few chronically ill people in these trials, neither the 'active' tetracycline bacteriostatic agent, oral demeclocycline, nor the opiate antagonist naloxone, nor placebo, gave any suggestion of serious adverse effects for a period of up to six weeks. The two small studies did not report any useful data on measures of polydipsia, physical symptoms secondary to increased fluid intake, mental state, general functioning or economic outcomes.

The trials offer little to the clinician hoping to treat psychosis-related polydipsia with drugs, except that further evaluative studies need to be conducted in this area. Treatment of any sort for psychosis related polydipsia might only be informative within a well designed, conducted and reported randomised study. The two pioneering studies suggest that larger trials, though difficult, would not be impossible with adequate support and co-ordination.