Objective: This study investigated whether measurement of plasma levels may be useful in monitoring clinical efficacy and side effects during oral haloperidol (HL) treatment of psychosis and behavioral dyscontrol in patients with Alzheimer disease (AD).
Methods: After a single-blind placebo period of 1 week, 71 outpatients with AD were randomized to a 6-week, double-blind, placebo-controlled trial of HL 2 mg-3 mg/day (standard dose), HL 0.5 mg-0.75 mg/day (low dose), or placebo, with plasma levels for HL drawn at the end of 6 weeks.
Results: Of the 40 patients who received active HL for 6 weeks, 35 had plasma levels drawn. Plasma levels were all below the lower limit of the postulated therapeutic range in schizophrenia. Nonetheless, HL plasma level significantly correlated with clinical efficacy as measured by reduction in Brief Psychiatric Rating Scale Total score, Psychosis factor, and Hostile-Suspiciousness factor, the Behavioral Syndromes Scale for Dementia Psychomotor Agitation scale, and with the severity of extrapyramidal side effects (EPS). Oral dose did not significantly correlate with any of these efficacy or side-effect measures. Plasma levels significantly correlated with HL dose. When both HL dose and HL plasma level were included as independent variables in linear-regression analyses, only HL plasma level was a significant predictor of efficacy and EPS.
Conclusion: Measurement of HL plasma levels may have potential usefulness as an adjunct in monitoring treatment response to oral HL in AD patients with psychosis or disruptive behavior.