Minimally Effective Doses of Conventional Antipsychotic Medications Used to Treat Aggression, Self-Injurious and Destructive Behaviors in Mentally Retarded Adults

Retrospective review of records from 1990 to 1997 revealed unsuccessful attempts to withdraw antipsychotic medications from a total of 34 intellectually disabled individuals. The lowest dose of antipsychotic medication necessary to maintain symptom suppression and the dose at which relapse occurred were noted. Target behaviors observed indicating relapse included increased self-injurious behavior, aggression, and destructive/disruptive behaviors. Nineteen subjects received a low potency antipsychotic agent (ie, thioridazine or chlorpromazine) and 15 received a high potency antipsychotic agent (ie, haloperidol, loxapine, thiothixene). The mean lowest effective dose of chlorpromazine/thioridazine was 149.3 mg/d and relapse occurred at a mean dose of 93.6 mg/d. The mean lowest effective dose of haloperidol or related high potency drugs (expressed as haloperidol equivalents) was 5.9 mg/d, and relapse occurred at a mean dose of 3.8 mg/d.