Dose-Dependent Impulse Control Disorders in Piribedil Overdose

We describe a 73-\year-\old female patient with Parkinson disease who developed impulse control disorders (ICDs) and dopamine dysregulation syndrome (DDS) owing to piribedil overdose. She was initially put on piribedil 150 mg; and owing to disease progression, levodopa was added 4 years later. Three years later, piribedil was raised to 200 mg; but presumably owing to a misunderstanding, she took 400 mg/d, which was well tolerated and produced an improvement in her parkinsonian symptoms. However, over the next few weeks, she started shopping compulsively, buying unnecessary clothes and food. In addition, she visited her dog's veterinarian several times a day with nonsense queries. She began to have financial problems and family disruption. During an examination, mild dyskinesia was evident. We diagnosed ICDs and most likely dopamine dysregulation syndrome DDS. Piribedil doses were decreased to 200 mg/d and levodopa increased up to 750 mg/d, with a clear improvement in compulsive behavior without worsening of the dyskinesia. Our case shows that even in cases in which regular doses of dopamine agonists are harmless, dose increments can induce these unwanted effects.