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Self-Induced WaterIntoxication Treated withRisperidone

Richard CMillson, MD1, Craig EEmes, MD

2, WilliamGGlackman, PhD

3

Objective: To determine whether or not risperidone is efficacious in treating self-induced water intoxication in

 patients with chronic schizophrenia.

 Method: We carried out a prospective 11-month open-label study using risperidone to treat 8 men with chronic

schizophrenia and self-induced water intoxication.

 Results: The 8 men were not able to reduce their fluid consumption compared with their baseline intake.

 Risperidone, however, significantly decreased the Brief Psychiatric Rating Scale (BPRS) scores of this very

chronic group.

Conclusions: Although risperidone decreased schizophrenic symptoms, it did not have significant efficacy in

treatingself-inducedwaterintoxication. Thisstudy mayhaveimplications for the treatmentof addictive behaviour.

(Can J Psychiatry 1996;41:648–650)

 Key Words: water intoxication, polydipsia, risperidone, clozapine, schizophrenia, addiction

Self-induced water intoxication is a common and serious

problem. Polydipsia occurs in over 20%andwater intoxi-

cation in up to 5% of chronic psychiatric inpatients, the

majority of whom have schizophrenia (1). Case reports have

indicated clozapinemay be beneficial in treatingself-induced

water intoxication (2–5). This raises the hope that we may be

able to treat self-induced water intoxication with serotonin–

dopamine antagonists. Clozapine has significant side effects,

however, and is fairly costly.

Risperidone is a potent dopamine and serotonin-2A

(5-HT2A) blocker that has been shown to be superior overall

to haloperidol in the management of chronic schizophrenia

(6). A recent case report has described the successful treat-

ment of polydipsia and hyponatremia with risperidone in a

53-year-old man with schizophrenia (7). Clinically, we have

also noted that risperidone seems to decrease fluid

consumption in patients with chronic schizophrenia and self-

induced water intoxication. We carried out a prospective

open-label study to determine whether risperidone may be

useful in treating the latter condition.

Method

We selected 8 consecutive men (mean age ± SD = 44.4 ±

9.9 years) who we were starting risperidone treatment and

who met DSM-III-R criteria for chronic schizophrenia. We

obtained written informed consent after giving the subjects a

complete description of the study. Their mean duration of 

hospitalization was 16.7 ± 9.0 years. All participants had a

long history of polydipsia and episodic water intoxication.

They had resided on the 25-bed all-male Water Intoxication

Unit at Riverview Hospital for an average of 5.4 ± 3.3 years.

We have characterized patients on this unit in a previous

report (8).

Wemonitored thefluidintake of thepatients foran 8-week 

period by weighing them 4 times per day. We calculated the

daily maximum percent increase in body weight with respect

to their 07:30 baseline weight. Serial body weight measure-

ment is a useful way of monitoring changes in hydration (9).

We completed the BPRS for 7 of the 8 men.

We then started them on risperidone in doses up to

16 mg/day. We tapered and then discontinued their previous

antipsychotic medication over 2 weeks. We tried to minimize

changes to their medications over the study period. We

Manuscript received February 1996, revised July 1996.1Director, Acute Assessment and Treatment Program, Riverview Hospital,Port Coquitlam, British Columbia.2Third-Year Psychiatry Resident, McGill University, Montreal, Quebec.3Consulting Psychologist, Riverview Hospital, Port Coquitlam, BritishColumbia.From Riverview Hospital in Port Coquitlam, BC and the Department of Psychiatry, University of British Columbia, Vancouver, BC.

 Address reprint requests to: Dr RC Millson, Riverview Hospital, 500Lougheed Highway, Port Coquitlam, BC V3C 4J2

CanJPsychiatry, Vol 41, December 1996

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continuedto monitor fluid intakeby weighing themen4 times

perday over a 6-month period. Weagaincompletedthe BPRS

for those assessed previously.

When we started the study, optimal dosing for risperidone

had not been determined. During the study, we learned that

the optimal dose for risperidone was from 6 to 8 mg/day. Atthe end of the 6-month period, we decided to extend the study

using the optimal dose. We reduced the patients’ risperidone

dosage to 8 mg/day. We then waited one month to allow the

patients time to stabilize on the lower dose. Following the

stabilization period, we continued to monitor fluid intake by

weighing the men 4 times per day over a further 2-month

period.

Results

Following the first 6 months of treatment, the mean daily

percent change in body weight declined slightly but not

significantly (baseline [mean ± SD] = 3.89% ± 0.81%; after6 months of risperidone treatment = 3.60% ± 0.56%; df 7, t =

1.31, P = 0.23).Theaverage risperidonedose was 13 mgover

the 6-month treatment period (range 11 to 15 mg/day). There

was,however, a significant improvement inclinicalcondition

as assessedby the BPRS (baseline= 24.7 ± 5.6; after 6 months

of risperidonetreatment = 14.7 ± 4.8; df 6, t = 3.49,P = 0.013).

Following the additional 3 months of treatment at the

lower dose, the mean daily percent change in body weight

slightly declined with respect to baseline, but again, it did not

decline significantly (baseline = 3.89% ± 0.81%; posttreat-

ment = 3.49% ± 0.79%; df 7, t = 1.49, P = 0.18). The mean

risperidone dose was 8 mg/day during the last 2 months of thestudy.

Discussion

Though there was a trend toward decreased fluid intake,

our clinical impression that risperidonedecreasedfluid intake

in schizophrenicpatientswith self-inducedwaterintoxication

was not upheld by our study. Risperidone did have a signifi-

cant effect, however, in improving clinicalstatus as measured

by theBPRS. Themarked improvement in clinicalstatus may

have caused staff to perceive, through a “halo” effect, that

risperidone was helping patients to decrease their fluid intake

significantly. Risperidone may still be useful in the treatment

of self-induced water intoxication because patients who

suffer fewer psychotic symptoms would be able to derive

greater benefit from group psychotherapy and behaviour

therapy.

It is possible that risperidone may be more efficacious at

a lower dose than we used in this study. It is alsopossible that

using a large dose of risperidone initially biased the results.

If this were the case, however, we would have expected a

more robust response when we reduced the dose. Our study

does not address theuseof adjunctive agents, such as lithium,

to augment the effect of risperidone. This possibility needs to

be explored further.

This study may have theoretical interest in the treatment

of addiction. Although the etiology of self-induced water

intoxicationremains unknown, we have suggestedthat it may

be a form of addictive behaviour(8,10). It hasbeenpostulatedthat clozapine has an antiaddictive effect in schizophrenia

(11,12). Case reports also suggest clozapine is efficacious in

treating self-induced water intoxication (2–5). Clozapine and

risperidone have a markedly different spectrum of action on

receptors (13). In particular, risperidone is a much more

potent 5-HT2A blocker (13). Clozapine, in contrast, blocks

muscarinic, 5-HT1, 5-HT2C, and 5-HT3 receptors, none of 

which is blocked by risperidone (13). If clozapine proves to

be more efficacious at treating self-induced water intoxica-

tion than risperidone, valuable clues may be gained as to

which receptors are important in addiction.

Clinical Implications

• Risperidone did not have a significant antipolydipsic effect.

• Risperidone may, however, help these patients to be moreamenable to group and behaviour therapy.

Limitations

• Open-label, all-male study.

• Patients all had a chronic problem with self-induced waterintoxication.

• Use of adjunctive agents was not addressed.

Acknowledgement

The authors thank Bradley W Macdonald for help with the datapreparation.

References

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9. Delva NJ, Crammer JL. Polydipsia in chronic psychiatric patients: body weight

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Résumé

Objectif : Déterminer l’efficacité de la rispéridone pour traiter l’autointoxication hydrique chez des patients

atteints de schizophrénie chronique.

 Méthode : Nous avons mené une étudeprospectiveouverted’uneduréede 11 mois sur le traitementà la rispéridone

de 8 hommes atteints de schizophrénie chronique et d’autointoxication hydrique.

 Résultats : Les 8 hommes étaient incapables de réduire leur consommation de liquides par comparaison avec leur 

apport de départ. Cependant, la rispéridone a beaucoup réduit les scores de ce groupe très chronique à l’échelle

abrégée d’appréciation psychiatrique (Brief Psychiatric Rating Scale, BPRS).

Conclusions : Bien que la rispéridone ait réduit les symptômes de schizophrénie, elle n’est pas très efficace pour 

traiter l’autointoxication hydrique. Cette étude aura peut-êtreune incidence sur le traitement d’uncomportement  pouvant engendrer une dépendance.

650 TheCanadianJournal of Psychiatry Vol 41, No 10