Olanzapine in the treatment of hallucinosis in idiopathic Parkinson's disease: a cautionary note

BACKGROUND: Hallucinosis is a dopaminergic dose limiting complication of the treatment of idiopathic Parkinson's disease. Typical neuroleptic medications cannot be used for suppressing hallucinosis because the extrapyramidal side effects worsen parkinsonian motor control. Olanzapine is a novel atypical antipsychotic drug with few reported extrapyramidal side effects which may be more suitable for controlling hallucinosis in these patients. METHODS: Olanzapine was given to five patients with idiopathic Parkinson's disease and the dosage was titrated until a clinically meaningful reduction in hallucinosis was achieved. The commercially available 5 mg, 7.5 mg and 10 mg tablets were used. RESULTS: After an initial 9 days of treatment, hallucinosis frequency was significantly reduced, an effect which was maintained with continued treatment. However, during this early phase of treatment, parkinsonian motor disability increased, which resulted in two of the patients discontinuing medication. CONCLUSIONS: Olanzapine is effective in the suppression of hallucinosis in patients with idiopathic Parkinson's disease but the currently available dose increments may result in an unacceptable exacerbation of motor disability.