Maropitant in Cats Undergoing Ovariohysterectomy: Evaluation of Clinical and Analgesic Effects

Abstract

Background: Emesis is a frequent adverse effect associated with the use of α2-adrenergic agonists and opioids in veterinary medicine, particularly in cats, where it’s incidence can reach up to 80%. Maropitant, a neurokinin-1 (NK1) receptor antagonist, has demonstrated potent antiemetic properties and potential analgesic effects, making it a promising candidate for perioperative management. However, its efficacy in modulating intraoperative and postoperative analgesia in cats undergoing ovariohysterectomy (OH) remains underexplored. 

Materials, Methods & Results: A double-blinded, randomized clinical trial was conducted with 16 healthy female cats divided into 2 groups. The maropitant group (MG) received 1 mg/kg subcutaneously 1 h prior to preanesthetic medication with dexmedetomidine (5 μg/kg) and morphine (0.3 mg/kg), while the control group (CG) received an equivalent volume of saline. Anesthesia was induced with propofol and maintained with isoflurane. Intraoperative parameters, including heart rate (HR), systolic arterial pressure (SAP), and fentanyl rescue requirements, were monitored. Postoperative analgesia was assessed using the UNESP/Botucatu multidimensional feline acute pain scale, with rescue analgesia administered as needed. Maropitant effectively prevented vomiting, with no instances of emesis observed in the MG, compared to a 62.5% incidence in the CG (P = 0.0256). HR and SAP increased during periods of heightened surgical stimulation in both groups, reflecting physiological responses to nociception; however, these increases were less pronounced in the MG, suggesting partial modulation of visceral pain. Intraoperative fentanyl rescues were significantly fewer in the MG (median: 9) compared to the CG (median: 13), particularly at moments of intense nociception (P = 0.0486). Postoperative pain scores showed no significant differences between groups, with both requiring similar numbers of rescue analgesia interventions during the evaluation period. Signs of nausea, such as sialorrhea and lip-licking, were observed in both groups, with no statistical differences, indicating that maropitant’s antinausea efficacy may be limited.

Discussion: The findings highlight the dual role of maropitant as an antiemetic and adjunctive intraoperative analgesic. It’s complete inhibition of vomiting underscores it’s efficacy in blocking emetic signaling pathways via NK1 receptor antagonism in the brainstem vomiting center, particularly against stimuli from α2-adrenergic agonists and opioids. This antiemetic effect is clinically significant, improving the welfare of cats undergoing OSH by eliminating a common and distressing adverse effect. Furthermore, the reduction in intraoperative fentanyl rescues suggests that maropitant’s modulation of visceral nociception is effective, potentially linked to its ability to inhibit substance P-mediated nociceptive transmission in visceral afferents. However, the lack of significant differences in postoperative pain scores and analgesic rescues between groups suggests that maropitant’s analgesic efficacy may be dose-dependent or limited to the intraoperative period. In conclusion, Maropitant at a dose of 1 mg/kg administered subcutaneously is a valuable addition to perioperative protocols in cats undergoing OSH, effectively preventing vomiting and reducing intraoperative analgesic requirements. Further research is warranted to optimize dosing strategies and explore its integration within multimodal analgesic protocols to enhance its clinical applications.

Keywords: maropitant, cats, emesis, pain.