Methylphenidate-induced obsessive-compulsive symptoms in an elderly man.

An 82-year-old man with treatment-resistant depression and early Alzheimer's disease was started on methylphenidate. Significant obsessive-compulsive behavior ensued but diminished over several weeks when methylphenidate was replaced by fluvoxamine. The patient had no prior psychiatric history, but he had a sister with obsessive-compulsive disorder. It appears that methylphenidate precipitated the patient's pathological behavior.