Haloperidol blood levels during dosage reduction in chronic schizophrenic patients.

Haloperidol levels were measured by radioreceptor assay in 12 schizophrenic patients during gradual dosage reduction (at 10-day) intervals) from 60 to 0 mg/day. Serum levels were highly correlated with the oral dose in each patient, but poorly correlated across patients. Clinical deterioration appeared only 10-20 days after total cessation of the oral drug, and so it was not possible to determine an optimal blood level for chronic maintenance. Below oral dosage of 10 mg/day of haloperidol many patients' blood levels are undetectable by the radioreceptor method.