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.