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Extrapyramidal side effects with risperidone and haloperidol at comparable D2 receptor occupancy levels.

M B Knable·A Heinz·T Raedler·D R Weinberger
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Abstract

Risperidone is an antipsychotic drug with high affinity at dopamine D2 and serotonin 5-HT2 receptors. Previous clinical studies have proposed that risperidone's pharmacologic profile may produce improved efficacy for negative psychotic symptoms and decreased propensity for extrapyramidal side effects; features shared by so-called 'atypical' neuroleptics. To determine if routine risperidone treatment is associated with a unique degree of D2 receptor occupancy and pattern of clinical effects, we used [123I]IBZM SPECT to determine D2 occupancy in subjects treated with routine clinical doses of risperidone (n = 12) or haloperidol (n = 7). Both risperidone and haloperidol produced D2 occupancy levels between approximately 60 and 90% at standard clinical doses. There was no significant difference between occupancy levels obtained with haloperidol or risperidone. Drug-induced parkinsonism was observed in subjects treated with risperidone (42%) and haloperidol (29%) and was observed at occupancy levels above 60%. Based on these observations, it is concluded that 5-HT2 blockade obtained with risperidone at D2 occupancy rates of 60% and above does not appear to protect against the risk for extrapyramidal side effects.

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AdultAntipsychotic AgentsBasal Ganglia DiseasesBenzamidesBrainBrain MappingDopamine AntagonistsDrug Therapy, CombinationFemaleHaloperidolHumansMaleMiddle AgedNeurologic ExaminationParkinson Disease, SecondaryPyrrolidinesReceptors, Dopamine D2RisperidoneTomography, Emission-Computed, Single-PhotonJournal Article

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M B Knable, A Heinz, T Raedler, D R Weinberger. 1997-09-29. Extrapyramidal side effects with risperidone and haloperidol at comparable D2 receptor occupancy levels.. https://doi.org/10.1016/s0925-4927(97)00023-1

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