Haloperidol decanoate in chronic schizophrenia: a study of 12 months with plasma levels.

1. Clinical activity, extrapyramidal side-effects were evaluated in 22 schizophrenic out patients diagnosed according to DSM III and treated with haloperidol decanoate (50-300 mg i.m. monthly dose) for 12 months. 2. BPRS total scores did not show significant fluctuations showing a clinical stability of the patient population. 3. Patients with a duration of illness greater than 10 yrs (Group 2) showed significant (p less than 0.01) higher EPSE total scores compared to those with a duration of illness less than 10 yrs (Group 1). 4. A positive correlation was found between the administered dose and haloperidol plasma levels. 5. Patients from Group 2 reached the steady-state more slowly and showed a lower total L/D ratio compared to those from Group 1. 6. The pharmacokinetic approach seems desirable in order to adjust the dose and avoid schizophrenic relapses.