Gabapentin-induced myoclonus: a case report

Abstract

Objective: To present a case of myoclonus secondary to gabapentin use in a patient with no epilepsy or renal disease. Background: Myoclonus may be linked to a variety of causes, including epilepsy, postanoxic brain injury, metabolic encephalopathies and focal central nervous system lesions. Various drugs also have been reported to induce myoclonus. Gabapentin-induced myoclonus has been reported previously, especially in cases with impaired renal function or epilepsy. Method: Case report Results: A 68-year-old male presented with hand tremors starting 2 weeks after the initiation of 1800 mg daily gabapentin recommended for distal neuropathic pain. Examination revealed bilateral action-induced clonus in the hands. His mental status was normal, and there was no weakness. Ankle reflexes were normal, and plantar reflexes were flexor. There was mild hypesthesia of the distal lower extremities. Routine blood tests including urea, creatinine, electrolytes and thyroid function tests were normal. Gabapentin levels were not determined. Gabapentin was discontinued, and his symptoms spontaneously resolved 2 days after discontinuation of gabapentin. Conclusions: The close time relationship between gabapentin initiation and onset of myoclonus, and the rapid resolution of symptoms after withdrawal of the drug suggested that gabapentin played a causative role in our patient. Pathophysiological mechanisms of gabapentin-induced myoclonus remain poorly understood. It has been suggested that the serotonin neurotransmitter system may be involved in the pathogenesis. Administration and dose escalation of gabapentin should be performed with caution, and gabapentin should be always considered as a potential etiology for myoclonus.