Infusion-rate-dependent Acute Neuropathic Pain with Duopa in a Patient with Parkinson's Disease and Pre-existing Neuropathy

The association of peripheral neuropathy (PN) with the cumulative use of levodopa, presumably by vitamin B12 deficiency, has been well-documented in the literature. However, less is known about the L-dopa infusion-rate-dependent precipitation of pre-existing peripheral neuropathy. We report an unusual case of Parkinson’s disease in a patient who presented with acute exacerbations of pre-existing peripheral neuropathy on exceeding certain rates of continuous Carbidopa-Levodopa Infusions (CLI). We present a case of a 68-year-old gentleman with a 20-year history of idiopathic Parkinson's disease with bilateral subthalamic nucleus deep brain stimulation who was started on Duopa therapy for worsening dyskinesias. Workup before initiating Duopa was significant for idiopathic sensorimotor axonal polyneuropathy, although the symptoms were well controlled with medications. Subsequently, the patient developed severe neuropathic pain within 24 hours of initiating Duopa characterized by burning and stinging in his feet. Symptoms resolved within four hours of reducing the continuous infusion rates without modifying the bolus doses. The patient was doing well with extra bolus doses to manage off periods with no further recurrence of symptoms. With the support of this case report, we would like to conclude that the acute worsening of neuropathic pain with infusion rate or duration of treatment might limit the clinical benefits of Duopa and adds to the expanding spectrum of neurotoxic side effects associated with this therapy. Further prospective studies are needed to monitor the acute worsening of neuropathic pain in patients with pre-existing PN, after initiating CLI and its association with doses of levodopa/carbidopa.