Intrathecal oxybuprocaine and proxymetacaine produced potent and long-lasting spinal anesthesia in rats

Proxymetacaine and oxybuprocaine were clinically used for topical ocular anesthesia but never for spinal anesthesia, and therefore spinal anesthetic effects of proxymetacaine and oxybuprocaine were performed and compared with bupivacaine and lidocaine. After rats were injected intrathecally with proxymetacaine, oxybuprocaine, bupivacaine, and lidocane, dose-response curves were constructed. We evaluated the potencies (ED₅₀) and durations (time to full recovery) of proxymetacaine and oxybuprocaine on spinal blockades of motor function, proprioception, and nociception and compared with bupivacaine and lidocaine in rats. We found that proxymetacaine and oxybuprocaine acted like bupivacaine or lidocaine and produced dose-related spinal blockades of motor function, proprioception and nociception. On the ED₅₀ basis, the ranks of potencies in motor, proprioception, and nociception were proxymetacaine > oxybuprocaine > bupivacaine > lidocaine (P < 0.01 for the differences). On an equipotent basis (ED₂₀, ED₅₀, ED₈₀), oxybuprocaine and bupivacaine produced similarly longer spinal blockades than did proxymetacaine or lidocaine (P < 0.05 for the differences). Intrathecal proxymetacaine, oxybuprocaine, and bupivacaine also produced longer sensory blockade than motor blockade. These data demonstrated that oxybuprocaine and proxymetacaine produced more potent spinal blockades, when compared with bupivacaine or lidocaine. Oxybuprocaine and bupivacaine with a more sensory-selective action over motor blockade produced longer spinal blockade than did proxymetacaine or lidocaine.