Preoperative Tapentadol Enhances the Depth of Anesthesia-Induced Sleep, Recovery Profile, and Serotonergic Modulation in Dogs Undergoing Ovariectomy with Propofol–Sevoflurane Anesthesia

Background: Optimizing pain control and anesthesia stability is essential for surgical outcomes in dogs. This study evaluated the effects of preoperative tapentadol on anesthesia depth, recovery, and serotonin levels in dogs undergoing elective spaying. Methods: Sixty-six healthy female dogs were randomly assigned to three groups: standard pain relief, tapentadol alone, or tapentadol combined with standard pain relief. Anesthesia was induced with propofol and maintained with sevoflurane. Intraoperative heart rate, blood pressure, anesthetic depth, postoperative sedation, pain scores, and plasma serotonin concentrations were recorded. Results: Tapentadol-treated dogs showed deeper and more stable anesthesia during surgical stimulation, higher early postoperative sedation that resolved within two hours, and reduced postoperative serotonin levels compared with controls. All analgesic protocols maintained adequate pain control, and biochemical parameters remained within normal limits. Conclusions: Preoperative tapentadol enhances anesthetic stability, supports smoother early recovery, and modulates serotonin levels in dogs, suggesting benefits for perioperative pain management and overall surgical welfare.