To evaluate butorphanol and tramadol as adjuvants to lidocaine in dogs undergoing mandibular nerve block. Fifteen beagles were allocated to groups based on the following treatments: lidocaine alone (L group), lidocaine + butorphanol (LB group), or lidocaine + tramadol (LT group). After mandibular nerve block with opioids as an adjunct to local anesthetics, the onset time, duration of action, and depth of anesthesia were evaluated using a quantitative method through neuromuscular blockades (NMBs) monitoring. The onset time of nerve block was 4.60 ± 2.06 min, 2.00 ± 0.00 min, and 2.60 ± 1.62 min in the L, LB, and LT groups, respectively; however, there was no statistically significant difference. The duration of nerve block was 111.88 ± 34.78 min, 302.00 ± 76.72 min, and 260.40 ± 49.88 min in the L, LB, and LT groups, respectively, with a significant difference between L and LB groups. The LB group demonstrated a more profound depth of anesthesia compared to the L and LT groups. In this study, using a quantitative method through NMBs monitoring, it was demonstrated that lidocaine and butorphanol in combination can increase the duration of nerve block and more profound the depth of anesthesia rather than lidocaine alone. Additionally, the combined use of lidocaine and opioids presented an objective indicator that could provide a more clinically stable nerve block.