Optimal haloperidol dosage in first-episode psychosis.

OBJECTIVE: To determine optimal doses of haloperidol for the treatment of a first episode of psychosis. METHOD: A 4-week prospective controlled clinical trial with "optimal dose" defined as the dose at which either of the following occurs: 1) significant improvement, defined as a 15% or greater decrease in scores on the Positive And Negative Syndrome Scale (PANSS), or 2) the onset of extrapyramidal symptoms. Beginning with 2 mg daily, haloperidol was increased weekly to 5 mg, 10 mg, and finally 20 mg daily until either 1) or 2) occurred. RESULTS: Optimal doses for the 36 subjects were 2 mg daily for 15 subjects, 5 mg daily for 11, 10 mg daily for 7, and 20 mg daily for 3. On average, subjects whose optimal dose was 2 mg daily showed the greatest improvement. Among the 27 subjects evidencing clinical response to treatment, 20 had plasma haloperidol levels below 5 ng/ml. CONCLUSION: Many people suffering a first psychotic episode respond to haloperidol doses well below levels in common use.