Serum concentration of eperisone hydrochloride correlates with QT interval.

BACKGROUND: Eperisone hydrochloride is a centrally acting muscle relaxant prescribed for muscle stiffness that acts by depressing the activities of α and γ efferent neurons in the spinal cord and supraspinal structures. Although a case of eperisone-induced severe QT prolongation had been reported, the relationship between serum eperisone concentration and QT interval remains obscure.

OBJECTIVE: The aim of this study was to investigate the relationship between serum eperisone concentration and QT interval.

METHODS: Four patients who overdosed on eperisone were admitted to our hospital between January 2010 and December 2011. We took simultaneous serial measurements of serum eperisone concentration and QT interval in the intensive care unit. In total, 22 measurement points were plotted for these patients. We analyzed the correlation between the serum eperisone concentration and corrected QT (QTc) interval.

RESULTS: Three men and one woman (mean age, 50 years) overdosed on eperisone with an average dose of 3087.5 mg (therapeutic dose, 150 mg/day). The mean QTc interval at arrival was 592 ms (range, 444-825 ms), and the mean serum eperisone concentration at arrival was 1257.5 ng/mL (range, 14.5-4120.0 ng/mL). The correlation coefficient was 0.833 between serum eperisone concentration and QTc interval (P < .001).

CONCLUSION: Serum eperisone concentration correlates with QTc interval in patients who overdose on eperisone.