Reduction of spastic increased muscle tone in multiple sclerosis by the nonopioid analgesic flupirtine

Objectives: A reduction of muscle tone in rats can be found after intraperi toneal or intrathecal injection of flupirtine in analgetic doses. However,a muscle-relaxing effect in patients with spasticity has not yet been shown. In this study we investigated whether flupirtine can reduce the increased muscle tone in patients with spasticity. Methods: The muscle-relaxing effect of flupirtine was compared to that of t etrazepam and of placebo in a randomised, double-blind, cross-over design. Altogether 9 patients with spastically increased muscle tone of the lower l imbs were investigated. The EMG activity integral of the rectus femoris mus cle was chosen as quantitative parameter for degree and change of muscle to ne. The EMG activity integral was measured using a dynamic bicycle ergomete r 60, 120 and 180 min after administration of the tested drugs. The degree of spasticity was measured as the quotient of the EMG activity integral of the active and passive rotation phase. This quotient is inversely proportio nal to the spastic muscle activity. Results: With flupirtine a significant increase in the EMG activity integra l was found after 60 min (maximum effect). From 120 min it showed a slow de cline. With tetrazepam the maximal effect was reached after 180 min. Placeb o did not change the EMG activity integral during the experiment. Conclusion:These results support the thesis that flupirtine has a muscle-re laxing effect in patients with pathologically increased muscle tone.