Effect of oral tizanidine on prolongation of intrathecal lidocaine

In order to prolong the duration of intrathecal lidocaine, various drugs are used along with it. Due to the promising effects of tizanidine on central nervous system, it can be assumed that tizanidine can have a positive effect on increasing the anesthesia duration too. Thus, we aimed to investigate the effect of oral tizanidine on the duration of lidocaine spinal anesthesia.
This double blind clinical trial was conducted on 40 male patients waiting for elective leg surgery with the age range of 20-60 years in one of the educational hospitals of Kerman University of Medical Sciences, Iran. We used simple random sampling and our participants were assigned into 2 groups (placebo and oral tizanidine receivers). Spinal anesthesia with 1 mg/kg of hyperbaric lidocaine 5% was performed in both groups. In tizanidine group, patients received 4 mg of oral tizanidine one hour before spinal anesthesia. Sensory block was examined by pin prick test and all anesthetic duration including start block until reduction of sensory level was calculated at 2 lower dermatomes.
Findings showed that oral tizanidine compared to placebo can cause a 10-15 minute increase in patients’ lidocaine spinal anesthesia. Therefore, the average anesthesia time for tizanidine group increased meaningfully (P = 0.03). In addition, tizanidine can sedate patients during surgery (P = 0.00) or in recovery (P = 0.003).
Based on the results, tizanidine increased the duration of lidocaine so oral tizanidine can be used to prolong the duration of lidocaine spinal anesthesia.