Effects of Maropitant Citrate or Acepromazine on the Incidence of Adverse Events Associated with Hydromorphone Premedication in Dogs

BACKGROUND: Vomiting is a common complication associated with the use of hydromorphine for pre‐emptive analgesia in dogs. The ideal anti‐emetic protocol for prevention of this complication has not been established. HYPOTHESIS: Maropitant administered concurrently or before hydromorphone would reduce the incidence of vomiting, signs of nausea, ptyalism, and increased panting compared to administration of acepromazine or a 0.9% saline control. ANIMALS: Sixty mixed‐breed female dogs scheduled for ovariohysterectomy. METHODS: Randomized, blinded, placebo‐controlled experimental study. Dogs were assigned to 4 experimental groups with 15 dogs per group. All groups received 0.2 mg/kg of hydromorphone IM. Group “Control” received 0.1 mL/kg saline SC 30–45 minutes before hydromorphone, group “Marop1” received 1 mg/kg maropitant SC 30–45 minutes before hydromorphone, group “Ace” received 0.02 mg/kg IM acepromazine 30–45 minutes before hydromorphone, and group “Marop2” received 1 mg/kg SC maropitant concurrently with hydromorphone. A trained and blinded observer documented adverse events from the time hydromorphone was administered until the time dogs were induced for surgery. RESULTS: Marop1 had significantly less vomiting (0%) compared to Control (87%; P < .01) and Ace (53%; P < .01). Marop2 had significantly less vomiting (27%) compared to Control (P < .01). Marop1 had significantly greater incidence of ptyalism (73%) compared to Ace (P < .01; 20%). Ace showed significantly less panting (33%) compared to Marop2 (93%; P < .01). CONCLUSIONS AND CLINICAL IMPORTANCE: In healthy dogs, maropitant citrate administered before hydromorphone significantly decreases the incidence of vomiting in dogs but does not improve signs of nausea, ptyalism, or increased panting.