Haloperidol blood levels and clinical outcome: a meta-analysis of studies relevant to testing the therapeutic window hypothesis.

Haloperidol, the most studied antipsychotic drug, is the only one about which reliable statements on the relationship between blood levels and clinical outcome can be made. A systematic overview was undertaken to determine whether there was an optimum blood concentration range for clinical efficacy. Eighteen published studies which provided individual patient data in tables or graphs were reviewed. Clinical benefits tended to decline when the haloperidol blood concentration was increased above 26 ng/ml. Our data support the existence of a therapeutic window between 4 and 26 ng/ml for haloperidol in the treatment of schizophrenic, schizoaffective and schizophreniform disorders.