Atypical
antipsychotic medications with lower affinities for D2 receptors are considered useful alternatives to treat
drug-induced
hallucinations in
Parkinson's disease (PD). We conducted a double-blind, placebo-controlled, unforced titration, parallel design study (2:1
drug to placebo randomization ratio) using
olanzapine (2.5-10 mg/day to effect) in 30 PD patients with
drug-induced
hallucinations. We performed an extensive battery of neuropsychological tests, the Unified Parkinson's Disease Rating Scale (UPDRS), assessments of on and off time at baseline and at 9 weeks after starting the medication. Sixteen patients on
olanzapine (mean dose, 4.6 mg/night) and 11 on placebo completed the study. Compared with placebo, performance on the UPDRS item 2 (thought disorder), and a structured interview for
hallucinations, both tended to improve on
drug but neither reached statistical significance. A neuropsychological test battery did not show any significant differences. Total on UPDRS motor scores (P < 0.05) and timed tapping (P < 0.01) worsened while on
drug compared to placebo.
Bradykinesia (P < 0.01) and gait (P < 0.001) items on the UPDRS largely accounted for this deterioration. After completion of the study, 8 of 16 patients randomly assigned to
drug continued
olanzapine at a mean dose of 2.4 mg/day. However, at the last recorded visit only 5 of 24 (20.8%) of all patients exposed to
drug (including those originally randomly assigned to placebo) remained on
olanzapine. In patients with PD, low-dose
olanzapine did not significantly improve
hallucinations but did worsen motor function.