Incidence of Post-Sedation Emesis in Cynomolgus (Macaca fascicularis) and Rhesus (Macaca mulatta) Macaques, and Evaluation of Prophylactic Antiemetic Efficacy

Abstract

Emesis is one of the most common side effects of ketamine sedation; however, predictors like species and sex have not been studied in macaques. This study aimed to determine the incidence and predictors of emesis in macaques undergoing ketamine sedation and to assess the efficacy of orally administered antiemetics in preventing emesis. A retrospective analysis was performed using medical records from rhesus and cynomolgus macaques who received ketamine sedation for veterinary examination events from August 2023 to April 2024. Among the 70 sedations performed using IM ketamine, the overall incidence of emesis was 26%. Cynomolgus macaques had a significantly higher risk of emesis (odds ratio (OR) 46.14, 95% confidence interval (CI): 7.08-493.9; p < 0.0001), with an emesis incidence of 55%. Females showed a higher incidence of emesis (75%) with an odds ratio of 3.72 (95% CI: 0.55-17.91; p = 0.24), though this difference was not statistically significant. In a prospective, randomized study, we compared the prophylactic use of oral maropitant citrate at a dose of 2 mg/kg or oral ondansetron at a dose of 1 mg/kg versus placebo for the prevention of emesis in cynomolgus macaques undergoing veterinary examination. Emesis was reduced from 58% in the control group to 50% in the maropitant group and 33% in the ondansetron group. However, the reduction in relative risk with either treatment did not reach statistical significance. Prophylactic oral administration of maropitant appears ineffective in preventing emesis in cynomolgus macaques. In contrast, prophylactic oral ondansetron is a more effective alternative in preventing emesis in these animals.

Keywords: antiemetic; cynomolgus macaque; emesis; maropitant citrate; ondansetron; rhesus macaque; sedation.

Figure 1

Study design, including a retrospective observational study and a prospective randomized trial. Animals in the retrospective observational study were administered ketamine for a scheduled sedated event, and emesis events were recorded post-sedation. In the prospective trial, animals were given randomized oral treatments (maropitant, ondansetron, or control) 2 h prior to sedation, shown as medication cups to indicate treatment groups and oral administration. The animals received ketamine and underwent veterinary examinations. The hourglass represents the recovery period during which emesis was monitored, and animals could consume food, indicated by food icons.

Figure 2

Incidence of emesis for maropitant and ondansetron versus placebo in cynomolgus macaques. Incidences of vomiting are presented (%), along with relative risk (RR). Both maropitant and ondansetron reduced the risk of vomiting, with an RR of 0.86 (0.3924 to 1.819) and 0.57 (0.2173 to 1.377), but this reduction was not significant.