Tizanidine is an orally-administered imadazoline-based compound that is widely used to reduce spasticity in a variety of conditions with most evidence for its effectiveness coming from trials with MS patients (Kaman et al. 2008). As an a2-adrenergic agonist it acts at both a spinal and supraspinal level.
A randomized, placebo-controlled trial specifically conducted to elucidate the anti-spasmodic effect of tizanidine revealed significant spasticity improvements in favour of tizanidine over placebo where Ashworth and Pendulum were the primary measures used (p<0.0001 and p<0.002, respectively; Nance et al. 1994; N=118). Although this study represents level 1b evidence, it is noteworthy to mention that 34% of subjects who received study treatment and discontinued prematurely due to adverse events, lack of efficacy and other reasons not specified, were not included in the study analysis. Another single dose, pre-post test study (Mathias et al. 1989; N=10) presented evidence to corroborate the reduction in spasticity as measured by Ashworth and furthermore revealed that muscle power was not affected at any stage in the study. More specifically, the impact of tizanidine on the spastic muscle was examined in a study by Mirbagheri et al. (2010) who found that on average there was a 25% reduction in peak-torque in the SCI subjects. Significant decreases in reflex stiffness post-tizanidine were found but not in intrinsic muscle stiffness.
There is level 1b evidence based on a single RCT to support the use of tizanidine for the treatment of SCI spasticity, although it is noteworthy that 34% of subjects who received study treatment and discontinued prematurely due to adverse events, lack of efficacy and other reasons not specified, were not included in the study analysis.
- Tizanidine may be useful in treating SCI spasticity.