Bilateral tonic seizures probably induced by eperisone hydrochloride: a case report

Abstract

Eperisone hydrochloride is a central muscle relaxant used to treat osteoporosis. Seizures are rare side effects of eperisone hydrochloride and have been previously reported in the medical literature in overdose situations but not at regular doses. This case report describes a 42-year-old male painter who developed severe bilateral tonic seizures after the initiation of eperisone hydrochloride at regular doses for low back pain. Symptoms gradually eased in the days following the discontinuation of eperisone hydrochloride and antiepileptic treatment, with no recurrence. This rare adverse drug reaction warrants clinical awareness; however, the mechanisms underlying these adverse reactions remain to be clarified.

Keywords: case report; drug; eperisone hydrochloride; muscle relaxant; seizures; tonic.

Figure 1

(A) Timeline of an episode of care. The patient ingested 50 mg tid of eperisone hydrochloride for the first 3 days with no adverse effects. However, on the morning of the 4th day, the patient experienced frequent bilateral tonic seizures. The following day, the patient was admitted to the hospital and treated with diazepam, sodium valproate, and rehydration, after which the symptoms decreased and did not occur on the morning of the 2nd day after admission. The head MRI was normal on the 2nd day after admission, sodium valproate was discontinued on the 3rd day after admission, and the 24-h video EEG from the 3rd to the 4th day after admission was normal. (B) EEG showing low-to-medium amplitude alpha background EEG predominantly at 8.5–11.5 Hz in the quiet, awake with closed-eye state (a), and K complex waves during sleep (b).

Figure 2

Naranjo adverse drug reaction probability scale (16). The score was calculated as +6 as eperisone hydrochloride has been previously reported to cause tonic seizures, myoclonic seizures, and epileptic spasms seizures, with aware or impaired awareness (14) and GTCS (13). The adverse event occurred after oral administration of eperisone hydrochloride and symptoms improved after discontinuing the drug. Other causes for bilateral tonic seizures were ruled out.