Effectiveness of dimenhydrinate and maropitant in preventing preoperative emesis and nausea in healthy dogs sedated with hydromorphone and dexmedetomidine: a randomized, blinded trial

To determine the anti-nausea and anti-emetic effects of dimenhydrinate and maropitant in dogs when given 60 minutes before hydromorphone and dexmedetomidine. Prospective, randomized, blinded, placebo-controlled clinical trial. A total of 87 healthy client-owned dogs undergoing ovariectomy/castration. Dogs were randomly assigned to be given maropitant (1 mg kg -1 ; group M) subcutaneously (SC), dimenhydrinate (4 mg kg -1 ; group D) intramuscularly (IM), or 0.9% NaCl (0.1 mL kg -1 ; group C) SC 60 minutes before anesthetic premedication with hydromorphone (0.1 mg kg -1 ) and dexmedetomidine (5–15 mcg kg -1 ) IM. Incidences of discomfort after injection of the treatment drug, nausea (ptyalism, lip licking, swallowing), and vomiting/retching were documented. Scores for nausea and sedation were assigned immediately before premedication and for 20 minutes after premedication. Data were analyzed using Fisher’s Exact test and Kruskal-Wallis test, with statistical significance set at p < 0.05. Discomfort to injection was significantly higher in group M (20/31, 64.5%) than in groups D (6/28, 21.4%) and C (2/28, 7.1%) ( p < 0.0001). Incidence of nausea was not significantly different between treatment groups [group M; 23/31 (74.2%) versus group D; 27/28 (96%) versus group C; 23/28 (82.1%), p = 0.050]. The incidence of vomiting/retching was significantly lower in group M (0/31, 0%) compared to groups D (15/28, 53.6%) and C (9/28, 32.1%) ( p < 0.0001). Dimenhydrinate produced no measurable anti-nausea and anti-emetic effect when given 60 minutes before hydromorphone and dexmedetomidine. Maropitant SC prevented hydromorphone-induced emesis but was ineffective in reducing nausea.