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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