Results of barbiturate antiepileptic drug discontinuation on antipsychotic medication dose in individuals with intellectual disability

Abstract

Five individuals with intellectual disability prescribed both a barbiturate antiepileptic drug (AED) and an antipsychotic medication were identified in a public residential facility. It was hypothesized that antipsychotic medication was prescribed at doses higher than necessary as a result of inadvertent barbiturate AED behavioural side-effects thought to be part of the underlying psychiatric or behavioural condition. To test this hypothesis, barbiturate AEDs were gradually reduced, and replaced with either carbamazepine or valproic acid, and antipsychotic medication was gradually reduced as well. Challenging behaviours, such as physical aggression, self-injurious behaviour and property destruction, were measured with a frequency count or partial interval recording, and retrospectively analysed for time periods of approximately 60 days before phenobarbital reduction, after phenobarbital discontinuation and after the lowest antipsychotic medication dose. Challenging behaviour collectively decreased by 81.5% after barbiturate discontinuation, mean antipsychotic medication dose significantly decreased from 146 mg day(-1) (SD = 98) to 106 mg day(-1) (SD = 88) chlorpromazine equivalence, and antipsychotic medication was discontinued in the cases of two individuals. Compared to the prebarbiturate AED reduction period, challenging behaviour collectively decreased by 96.3% after the lowest antipsychotic medication dose, which confirmed that reduced antipsychotic medication was not achieved at the expense of behaviour deterioration. The data supported the hypothesis that discontinuation of barbiturate AEDs results in decreased challenging behaviour and less antipsychotic medication.