Tizanidine is a centrally acting α2 agonist which has been used as a
premedication due to its
opioid-sparing and
sympatholytic properties. This systematic review assessed the safety and feasibility of oral
tizanidine. After registering the protocol with PROSPERO (CRD42022368546), randomized controlled trials and non-randomized observational studies were searched in various databases. The primary outcome was intraoperative
opioid use; the secondary outcomes were 24-hr
opioid consumption,
pain scores, time to rescue
analgesia, and adverse events. The risk of bias scale was used to assess the quality of evidence. Out of 202 studies identified, five studies fulfilled the inclusion criteria. Intraoperative
opioid consumption was significantly less in the
tizanidine group (MD: -2.40; 95% CI: -4.22, -0.59; P = 0.010; I2 = 0 %). The 24-hr
opioid consumption was comparable between both groups (MD: -42.53, 95% CI: -91.45, 6.39; P = 0.09; I2 = 99%). Time to rescue
analgesia was comparable between both groups (MD: 308.22; 95% CI: -263.67, 880.11, P = 0.29, I2 = 100%).
Pain scores at 6 and 12 hours were comparable (MD: -1.37; 95% CI: -3.68, 0.94; P = 0.24; I2 = 97%) and (MD: -1.76; 95% CI: -4.06, 0.53; P = 0.13; I2 = 95%); however, at 24 hours the scores were better in the
tizanidine group (MD: -1.10; 95% CI: -1.50, -0.69; P < 0.0001 I2 = 0%). Although dry mouth was significantly more in the
tizanidine group (MD: 5.35; 95% CI: 1.72, 16.62; P = 0.004; I2 = 0%),
postoperative nausea/
vomiting and
dizziness were comparable.
Tizanidine reduces intraoperative
opioid consumption without significant adverse events. However, it does not provide effective
opioid-sparing
analgesia or reduced
opioid requirement in the first 24 hours after surgery.