Clozapine treatment in a population of adults with mental retardation

Background: There is a paucity of data on the use of clozapine in patients with mental retardation and comorbid psychiatric illness. The authors describe their recent clinical experience using clozapine in treatment-refractory patients with mental retardation and severe psychiatric illness. Method: A retrospective review was performed on the records of all patients admitted to a university-affiliated, specialized inpatient psychiatry service who were selected for clozapine therapy from March 1994 through December 1997 (N = 33). Patients had DSM-IV diagnoses of schizophrenia, schizoaffective disorder, bipolar disorder, delusional disorder, or psychotic disorder NOS and were considered treatment resistant. All had deficits in functioning well beyond those expected for their degree of cognitive deficits and adaptive delays. Results: Of 33 initial patients, 26 remained on clozapine therapy for a follow-up duration of 5 to 48 months (mean = 24.8 months). Evaluation at follow-up revealed Clinical Global Impressions-Improvement (CGI-I) scores from 1 to 4 with a mean I SD improvement of 2.0 +/- 0.8 (much improved). The mean +/- SD rating of the CGI-Efficacy Index was 5 +/- 2.6 (decided improvement and partial remission of symptoms with no interference from side effects). The 6 patients who were not maintained on clozapine therapy over the study period did not significantly differ from the clozapine group in gender, race, age, side effects, or diagnosis. One patient was lost to follow-up. Side effects were mild and transient with constipation being the most common (N = 10). There were no significant cardiovascular side effects and no seizures. No patients discontinued treatment due to agranulocytosis. Conclusion: The current investigation lends support to the conclusion that clozapine appears to be safe, efficacious, and well tolerated in individuals with mental retardation and comorbid psychiatric illness.