Negative myoclonus induced by gabapentin and pregabalin: A case series and systematic literature review

Introduction: Negative myoclonus is a jerky, brief, and sudden interruption of voluntary muscle contraction. Although gabapentin and pregabalin have been reported to induce positive myoclonus in some patients with impaired renal function, there are only a few studies describing pregabalin- or gabapentin-induced negative myoclonus. This study reviewed patients who had developed pregabalin- or gabapentin-induced negative myoclonus. Methods: We collected the patients with negative myoclonus who were referred to the department of neurology at a university-affiliated hospital and selected pregabalin- or gabapentin-induced negative myoclonus. Then reviewed the literature with respect to pregabalin- or gabapentin-induced negative myoclonus. Results: A total of 77 patients with negative myoclonus were reviewed. Among them, 21 neuropathic pain patients who were prescribed and developed negative myoclonus induced by pregabalin (9 cases) or gabapentin (12 cases). To prove causality of the drug, probable and certain level of category according to the WHO-UMC criteria were recruited. Of the 21 patients, 3 had impaired renal function, while 18 had normal renal function. Review of the literature identified 7 further cases (6 had normal renal function) with pregabalin- or gabapentin-induced negative myoclonus. Conclusion: Pregabalin- and gabapentin-induced negative myoclonus can develop even in patients with normal renal function. Physicians should keep in mind the possibility of patients developing negative myoclonus under treatment of pregabalin or gabapentin even in short period of time and with low dosage, and in the normal range of renal function. Further prospective study investigating incidence and risk factors is warranted.