Background and Objectives The aim of this study was to compare the antinociceptive and motor-blocking effects of epidurally administered IQB-9302 (C₁₈ H₂₆N₂O. HCl) and bupivacaine in the dog.

Methods Twelve adult female Beagle dogs were used. Each animal received 3 concentrations (0.25%, 0.50%, and 0.75%) of either IQB-9302 (n = 6) or bupivacaine (n = 6) by means of a chronic epidural catheter. The nocifensive and motor-blocking status were determined at regular intervals before (baseline) and after drug administration.

Results Epidurally administered IQB-9302 caused a more potent nocifensive and motor-blocking action than bupivacaine. The duration of complete nocifensive block was the longest with IQB-9302, whereas the duration of dermatome nocifensive block was similar for both drugs. The nocifensive to motor block ratio was significantly higher with IQB-9302.

Conclusions IQB-9302 produced an anesthetic action similar to that of bupivacaine, although the former drug induced a slightly more potent nocifensive block. Nocifensive and motor block duration are very similar with IQB-9302, whereas bupivacaine induces a more prolonged motor block without nocifensive block.