Effects of Mephenoxalone and Tizanidine for Acute Painful Spasm of Paravertebral Muscles: A Randomized Double-Blind Control Study

Objectives: Skeletal muscle relaxants are frequently used to treat low back pain with spasm of paravertebral muscles. However, there is little comparative efficacy and safety data of different muscle relaxants. A randomized, doubleblind study was conducted to evaluate and compare the efficacy and safety of mephenoxalone and tizanidine in the 7-day treatment of adult patients suffering from acutely painful and moderately severe spasm of paravertebral muscles. Methods: A total of 41 Taiwanese patients were randomly allocated into mephenoxalone and tizanidine groups. Primary (muscle spasm severity, treatment responses) and secondary efficacy variables were obtained before and after treatments. Adverse events and several safety assessments were also recorded. Results: In a three item scale, muscle spasm severity was reduced by 0.90±0.55 and 0.95±0.67 points in the mephenoxalone and tizanidine groups, respectively. There was no significant difference between the two treatment groups in all variables for primary and secondary efficacy assessments. Nine mild to moderate adverse events were reported and one tizanidine-treated patient stopped the medication due to drug-induced urticaria. Transient slight drowsiness experienced in four mephenoxalone-treated patients did not hinder the treatment effect. Conclusion: This randomized, double-blind study demonstrates equivalent treatment efficacies of mephenoxalone and tizanidine in alleviating symptoms of acute painful paravertebral muscle spasms in Taiwanese patients. Both drugs with generally well tolerated.