Intrathecal rimantadine induces motor, proprioceptive, and nociceptive blockades in rats

The purpose of the experiment was to evaluate the local anesthetic effect of rimantadine in spinal anesthesia. Rimantadine in a dose-dependent fashion was constructed after intrathecally injecting the rats with four different doses. The potency and duration of rimantadine were compared with that of the local anesthetic lidocaine at producing spinal motor, nociceptive, and proprioceptive blockades. We demonstrated that intrathecal rimantadine dose-dependently produced spinal motor, nociceptive, and proprioceptive blockades. On the 50% effective dose (ED50) basis, the ranks of potencies at inducing spinal motor, nociceptive, and proprioceptive blockades was lidocaine > rimantadine (P < 0.01). Rimantadine exhibited more nociceptive block (ED50) than motor block (P < 0.05). At equi-anesthetic doses (ED25, ED50, and ED75), the spinal block duration produced by rimantadine was longer than that produced by lidocaine (P < 0.01). Furthermore, rimantadine (26.52 μmol/kg) prolonged the nociceptive nerve block more than the motor block (P < 0.001). Our preclinical data showed that rimantadine, with a more sensory-selective action over motor block, was less potent than lidocaine. Rimantadine produced longer duration in spinal anesthesia when compared with lidocaine.