Gabapentin or pregabalin induced myoclonus: A case series and literature review

Gabapentin (GBP) and pregabalin (PGB) are FDA approved for adjunctive treatment of partial seizures and for treatment of post-herpetic neuralgia. Both drugs are primarily eliminated by renal excretion. However, PGB or GBP induced myoclonus has only been reported infrequently in case reports/series. It is not discussed with patients and its sudden occurrence can lead to anxiety because of "seizure-like" nature. In addition, first-contact physicians might treat it as seizures, leading to unnecessary tests and aggressive management. Medical records of patients who had myoclonus because of PGB or GBP seen by Neurology service between Jan & May 2017 in inpatient or outpatient setting at our tertiary care setting were reviewed. We identified six patients who were on either GBP or PGB or both who developed likely subcortical myoclonus in the setting of renal insufficiency and one patient who developed myoclonus independent of renal dysfunction. Our results indicate that myoclonus is commonly seen in patients in various clinical settings with or without renal insufficiency, and is independent of the severity of the renal failure. However, this is a reversible side effect of medication and it resolves either by discontinuing the medication, removing the medication with hemodialysis or by improvement of renal dysfunction. With a high index of suspicion, aggressive testing and treatment for other possible conditions like seizures (in non-epilepsy patients) or CNS infections can be avoided. In patients with renal failure and with decreased physiological renal clearance such as the elderly, GBP or PGB dose initiation and changes should be conservative.