Helen C Pervanas, Laura R Daly
Pramipexole is a dopamine agonist used for the treatment of Parkinson's disease and restless leg syndrome. Amantadine is an antiviral agent with dopaminergic action that is approved for the treatment of motor symptoms associated with Parkinson's disease. This case report describes a patient with delusional parasitosis associated with concurrent use of pramipexole and amantadine. A 71-year-old man with a history of multiple sclerosis and Parkinson's disease presented with delusional parasitosis 4 months after his dose of pramipexole was increased from 0.75 mg/day to 4.5 mg/day. He was admitted to the geriatric psychiatric unit after his stool samples were found to be negative for parasites. A pharmacist evaluated his medications and noted that pramipexole and amantadine were independently associated with delusional parasitosis. Pramipexole and amantadine were subsequently discontinued, the patient was discharged and delusions completely resolved 4 months post-discontinuation. Concomitant use of pramipexole and amantadine may have led to delusional parasitosis. A literature review suggests that delusional parasitosis may be linked to striatal dopamine transporter dysfunction. In this case, the Naranjo Probability Score indicated that a drug-induced adverse event was "probable". The effects of these medications may have been enhanced by the patient's advanced age and the administration of pramipexole at the maximum recommended dose. Delusional parasitosis can occur in patients receiving concomitant treatment with pramipexole and amantadine. Patients receiving high doses of these agents in combination with other risk factors such as advanced age and impaired renal function should be monitored for symptoms of delusional parasitosis.