VetMedPerioperative vomiting in dogs: maropitant before anaesthesia prevents vomiting — but not reflux — LIKELY (the treatment made no difference to gastroesophageal reflux)
In dogs, does maropitant given before anaesthesia vs placebo reduce vomiting and regurgitation around induction and recovery?
Shelf #695 · gate-verified and displayed under the developer's blinded-trial rule
LIKELY (the treatment made no difference to gastroesophageal reflux): The claim splits cleanly in two. For vomiting around premedication and induction, maropitant given beforehand was consistently and completely effective in randomised blinded placebo-controlled trials: 0 of 9 maropitant dogs vomited after hydromorphone versus 6 of 9 on saline (Hay Kraus 2013, p = 0.0090); 0 of 13 retched or vomited versus 6 of 13 (46%) on saline, observed during the 20 minutes before induction (Johnson 2014, p = 0.015); 0 of 20 vomited on oral maropitant versus 5 of 20 (25%) on placebo (Hay Kraus 2014); and 0 of 31 vomited or retched versus 9 of 28 (32.1%) on saline in the largest vomiting trial (Shin 2026, p < 0.0001). For reflux/regurgitation, the same evidence base is null: Johnson 2014 found no difference in gastroesophageal reflux detected by oesophageal pH probe (4 of 13 maropitant dogs versus 6 of 13 saline dogs, no difference in reflux events), and Jones 2019 found no meaningful difference in postoperative clinical gastroesophageal reflux between dogs given preoperative maropitant plus metoclopramide and dogs given neither (93 dogs; no incidence figures in the record). Nausea signs were also largely unmoved (no difference in Hay Kraus 2014 and Shin 2026; reduced only in the smallest trial, Hay Kraus 2013). Design class (a): randomisation and blinding are both established by carded records' own wording ('Randomized, blinded, prospective clinical study' in Hay Kraus 2013, Johnson 2014 and Hay Kraus 2014; 'Prospective, randomized, blinded, placebo-controlled clinical trial' in Shin 2026). The honest limits: the vomiting trials are small (18–87 dogs), all challenge dogs with an opioid premedicant (hydromorphone, with acepromazine or dexmedetomidine) rather than measuring spontaneous perioperative vomiting across all protocols, observation windows are short (20–30 minutes after premedication in most), and no carded trial measured regurgitation as a standalone endpoint or aspiration outcomes — reflux was measured by pH probe or clinical signs. This shelf is distinct from Shelf #168 (maropitant vs metoclopramide for acute vomiting), whose claim-carrying records — including the morphine-premedication trial Lorenzutti 2017 — were desk-checked and are NOT re-carded here. Drafted Nov 10, 2026 (VetMed build, topic #695); all figures from abstracts fetched and verified at drafting.
Hay Kraus 2013: subcutaneous maropitant 1 hour before hydromorphone — 0 of 9 dogs vomited, retched or showed nausea, versus all 9 saline dogs affected (6 vomited, 1 retched, 2 showed nausea)
Randomized, blinded, prospective clinical study (record's own wording; publication type: Randomized Controlled Trial)
Who: Dogs: 18 dogs, ASA I/II, admitted for elective orthopedic surgical procedures — a mixed population of males and females, purebreds and mixed breeds, 1.0–10.2 years of age, weighing 3–49.5 kg. Dogs were randomly selected to receive subcutaneous maropitant 1.0 mg/kg (Group M) or saline 0.1 mL/kg (Group S) 1 hour prior to anaesthesia premedication with hydromorphone 0.1 mg/kg intramuscularly. A blinded observer documented vomiting, retching and/or signs of nausea for 30 minutes after premedication.
Result: All dogs in Group S vomited (6/9), retched (1/9) or displayed signs of nausea (2/9). None (0/9) of the dogs in Group M vomited, retched or displayed signs of nausea. Dogs in Group M had significantly fewer incidences of vomiting (p = 0.0090), vomiting and retching (p = 0.0023) and vomiting, retching and nausea (p < 0.0001) compared to Group S. The authors conclude maropitant prevents vomiting, retching and nausea associated with intramuscular hydromorphone administration in dogs.
Watch out: The smallest carded trial (9 dogs per group), and the only one in which nausea signs were also abolished — the larger trials below did not reproduce the nausea benefit, so the shelf's claim rests on vomiting and retching, not nausea. The observation window is the 30 minutes after premedication, before induction; nothing here measures vomiting during anaesthesia or recovery.
Hay Kraus BL. Efficacy of maropitant in preventing vomiting in dogs premedicated with hydromorphone. Vet Anaesth Analg. 2013;40(1):28-34. PMID: 23082784. Registry ID: none in the record. MeSH: Analgesics, Opioid/administration & dosage, adverse effects* · Animals · Antiemetics/therapeutic use* · Dog Diseases/chemically induced, prevention & control*, surgery · Dogs/surgery · Female · Hydromorphone/administration & dosage, adverse effects* · Injections, Intramuscular/veterinary · Male · Preanesthetic Medication/adverse effects* · Quinuclidines/therapeutic use* · Vomiting/prevention & control, veterinary*
Johnson 2014: intravenous maropitant prevented retching and vomiting (0/13 vs 6/13, p = 0.015) but did not prevent gastroesophageal reflux (4/13 vs 6/13) in anaesthetised dogs
Randomized, blinded, prospective clinical study (record's own wording; publication type: Randomized Controlled Trial)
Who: Dogs: 26 dogs admitted for elective soft tissue or orthopedic procedures, 3.1 ± 3.1 years of age, weighing 20.5 ± 11.4 kg. Dogs were randomly assigned to intravenous maropitant 1.0 mg/kg (Group M) or 0.9% saline 0.1 mL/kg (Group S) 45–60 minutes before premedication with hydromorphone 0.1 mg/kg and acepromazine 0.03 mg/kg intramuscularly. An observer blinded to treatment documented retching or vomiting for 20 minutes before induction with propofol and inhalation anaesthesia; a pH probe in the distal oesophagus detected gastroesophageal reflux (GER) during anaesthesia.
Result: None of the dogs in Group M retched or vomited (0/13); 6/13 (46%) in Group S were observed to retch or vomit, and the difference was significant (p = 0.015). There were no differences between groups in the number of dogs with GER (Group M: 4/13, Group S: 6/13) or the number of reflux events. Oesophageal pH at the end of anaesthesia was significantly lower in dogs with GER than dogs without GER in both groups. The author concludes intravenous maropitant prevented retching and vomiting associated with acepromazine–hydromorphone premedication but did not prevent the occurrence of GER, and that a larger study would be needed to determine whether the numerically fewer GER cases in Group M are a real difference.
Watch out: This is the shelf's pivotal card for the regurgitation half of the question: reflux was measured objectively by pH probe during anaesthesia, and the answer is a null on 13 dogs per group — the trial is too small to exclude a modest reflux effect, which is why the stamp says 'made no difference' on the evidence carded rather than claiming proof of no effect. Vomiting was observed only in the 20 minutes before induction.
Johnson RA. Maropitant prevented vomiting but not gastroesophageal reflux in anesthetized dogs premedicated with acepromazine-hydromorphone. Vet Anaesth Analg. 2014;41(4):406-10. PMID: 24330310. Registry ID: none in the record. MeSH: Acepromazine/administration & dosage, adverse effects* · Analgesics, Opioid/administration & dosage, adverse effects · Anesthesia, Inhalation/adverse effects, veterinary · Animals · Antiemetics/administration & dosage, pharmacology · Dog Diseases/chemically induced*, prevention & control · Dogs · Dopamine Antagonists/administration & dosage, adverse effects · Esophagus · Female · Gastroesophageal Reflux/chemically induced, prevention & control, veterinary* · Hydrogen-Ion Concentration · Hydromorphone/administration & dosage, adverse effects* · Male · Quinuclidines/administration & dosage, pharmacology* · Vomiting/chemically induced, prevention & control, veterinary*
Hay Kraus 2014: oral maropitant 2 hours before hydromorphone prevented vomiting (0/20 vs 5/20 on placebo) but not signs of nausea (60% vs 55%) in 40 dogs
Randomized, blinded, prospective clinical study (record's own wording; publication type: Randomized Controlled Trial)
Who: Dogs: 40 dogs with ASA status I or II, over 6 months of age, weighing 24–58.2 kg. Dogs were randomly selected to receive maropitant 2.0–4.0 mg/kg or placebo (lactose monohydrate) orally 2 hours prior to hydromorphone 0.1 mg/kg intramuscularly. A blinded observer recorded vomiting or signs of nausea (salivation or lip-licking) during a 30-minute period after hydromorphone administration.
Result: Of the 20 dogs receiving maropitant, none vomited but 12 (60%) developed signs of nausea. Of the 20 dogs receiving placebo, 5 (25%) vomited and 11 (55%) developed signs of nausea; overall, 16 of 20 (80%) dogs in the placebo group vomited or developed signs of nausea. Compared with placebo, maropitant significantly decreased the incidence of vomiting but not signs of nausea. Among the 40 study dogs, the overall incidence of vomiting associated with hydromorphone administration was 25%.
Watch out: The oral route at 2.0–4.0 mg/kg given 2 hours ahead — a different regimen from the 1 mg/kg injectable used in the other carded trials, and the placebo vomiting rate here (25%) is lower than in the injectable trials, so absolute benefit depends on the protocol's baseline risk. Nausea signs were as common on maropitant as on placebo: preventing vomiting is not the same as preventing nausea.
Hay Kraus BL. Efficacy of orally administered maropitant citrate in preventing vomiting associated with hydromorphone administration in dogs. J Am Vet Med Assoc. 2014;244(10):1164-9. PMID: 24786163. Registry ID: none in the record. MeSH: Administration, Oral · Analgesics, Opioid/administration & dosage, adverse effects* · Animals · Antiemetics/administration & dosage, therapeutic use* · Dog Diseases/chemically induced*, prevention & control · Dogs · Female · Hydromorphone/administration & dosage, adverse effects* · Male · Quinuclidines/administration & dosage, therapeutic use* · Vomiting/chemically induced, prevention & control, veterinary*
Shin 2026: in 87 dogs, subcutaneous maropitant before hydromorphone–dexmedetomidine gave 0% vomiting/retching versus 32.1% on saline (p < 0.0001), with no significant difference in nausea — and more injection discomfort (64.5% vs 7.1%)
Prospective, randomized, blinded, placebo-controlled clinical trial (record's own wording; publication type: Randomized Controlled Trial, Veterinary)
Who: Dogs: 87 healthy client-owned dogs undergoing ovariectomy or castration, randomly assigned to maropitant 1 mg/kg subcutaneously (Group M, n = 31), dimenhydrinate 4 mg/kg intramuscularly (Group D, n = 28), or 0.9% NaCl 0.1 mL/kg subcutaneously (Group C, n = 28), given 60 minutes before anaesthetic premedication with hydromorphone 0.1 mg/kg and dexmedetomidine 5–15 μg/kg intramuscularly. Nausea (ptyalism, lip licking, swallowing), vomiting/retching and injection discomfort were documented, with scores assigned immediately before and for 20 minutes after premedication.
Result: The incidence of vomiting/retching was significantly lower in Group M (0/31, 0%) compared to Group D (15/28, 53.6%) and Group C (9/28, 32.1%) (p < 0.0001). Incidence of nausea was not significantly different between groups (Group M 23/31, 74.2%; Group D 27/28, 96%; Group C 23/28, 82.1%; p = 0.050). Discomfort after 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). The authors conclude maropitant prevented hydromorphone-induced emesis but was ineffective in reducing nausea, and dimenhydrinate produced no measurable antinausea or antiemetic effect.
Watch out: The largest vomiting and most recent carded trial, and it replicates the pattern exactly: vomiting abolished, nausea not significantly reduced, and a real cost — subcutaneous maropitant injection discomfort in about two-thirds of dogs. The comparator dimenhydrinate arm is context only; the shelf's comparison is maropitant versus the saline control. Observation covered the premedication period for elective neutering surgery, not vomiting during anaesthesia or in recovery.
Shin CW, Ambros B. Effectiveness of dimenhydrinate and maropitant in preventing preoperative emesis and nausea in healthy dogs sedated with hydromorphone and dexmedetomidine: a randomized, blinded trial. Vet Anaesth Analg. 2026;53(4):101235. PMID: 42208176. Registry ID: none in the record. MeSH: Animals · Dogs · Female · Analgesics, Opioid/administration & dosage, adverse effects · Antiemetics*/therapeutic use, administration & dosage · Dexmedetomidine/administration & dosage, adverse effects · Dimenhydrinate*/therapeutic use, administration & dosage · Hydromorphone/administration & dosage, adverse effects · Hypnotics and Sedatives/administration & dosage, adverse effects · Nausea*/prevention & control, veterinary · Ovariectomy/veterinary · Quinuclidines*/therapeutic use, administration & dosage · Single-Blind Method · Vomiting*/prevention & control, veterinary · Male
Jones 2019: preoperative maropitant plus metoclopramide did not lower postoperative clinical gastroesophageal reflux versus no prophylaxis in 93 dogs (the treatment made no difference)
Randomised controlled trial (record's publication type: Randomized Controlled Trial, Veterinary; abstract states dogs were randomly assigned; blinding not stated in the record)
Who: Dogs: 93 client-owned dogs undergoing surgery at a university veterinary teaching hospital between March 2016 and February 2017, randomly assigned to an intervention group (preoperatively received maropitant citrate and metoclopramide hydrochloride) or a control group (did not preoperatively receive maropitant and metoclopramide). After surgery all dogs were recovered and monitored, and occurrences of clinical gastroesophageal reflux (GER) were noted.
Result: No meaningful difference in the incidence of clinical GER during the postoperative period was detected between the control and intervention groups. Variables associated with significantly increased odds of postoperative clinical GER were male sex (OR 9.2, 95% CI 1.26 to 195.0), overweight body condition score (OR 12.3, 95% CI 2.1 to 135.1), gastrointestinal surgery (OR 30.5, 95% CI 3.0 to 786.9) and requirement for a dexmedetomidine constant rate infusion after surgery (OR 9.6, 95% CI 1.3 to 212.5) — relative (odds) measures with very wide confidence intervals. The record's abstract gives no per-group GER incidence, so no absolute reflux rates can be stated from this record.
Watch out: The intervention combines maropitant with metoclopramide, so this trial cannot isolate maropitant's own effect on reflux — it is carded because it is the only randomised test of maropitant-containing prophylaxis against postoperative clinical reflux, and it agrees with Johnson 2014's pH-probe null for maropitant alone. The risk-factor odds ratios come from one 93-dog study with very wide intervals and are hypothesis-generating, not established risks.
Jones CT, Fransson BA. Evaluation of the effectiveness of preoperative administration of maropitant citrate and metoclopramide hydrochloride in preventing postoperative clinical gastroesophageal reflux in dogs. J Am Vet Med Assoc. 2019;255(4):437-445. PMID: 31355727. Registry ID: none in the record. MeSH: Animals · Dog Diseases/prevention & control* · Dogs · Dopamine D2 Receptor Antagonists/administration & dosage* · Female · Gastroesophageal Reflux/prevention & control, veterinary* · Male · Metoclopramide/administration & dosage* · Postoperative Care/veterinary · Quinuclidines
Synthesis: pre-anaesthetic maropitant reliably prevents opioid-premedication vomiting around induction (0% in every carded trial arm), but no carded trial shows it prevents gastroesophageal reflux/regurgitation, and nausea signs mostly persist
Synthesis
Who: Synthesis of the cards above: Hay Kraus 2013 (18 dogs, subcutaneous maropitant vs saline before hydromorphone), Johnson 2014 (26 dogs, intravenous maropitant vs saline before acepromazine–hydromorphone and inhalation anaesthesia, pH-probe reflux measurement), Hay Kraus 2014 (40 dogs, oral maropitant vs placebo before hydromorphone), Shin 2026 (87 dogs, subcutaneous maropitant vs dimenhydrinate vs saline before hydromorphone–dexmedetomidine) and Jones 2019 (93 dogs, preoperative maropitant plus metoclopramide vs none, postoperative clinical reflux).
Result: (1) Vomiting/retching after premedication: 0% on maropitant in all four placebo-controlled trials, versus 25% (oral-trial placebo), 32.1% (Shin saline), 46% retch/vomit (Johnson saline) and 6 of 9 vomited (Hay Kraus 2013 saline). (2) Reflux/regurgitation: no difference by pH probe during anaesthesia (4/13 vs 6/13 dogs with GER, Johnson) and no meaningful difference in postoperative clinical GER for maropitant-containing prophylaxis (Jones). (3) Nausea: abolished only in the smallest trial; not significantly different in Hay Kraus 2014 (60% vs 55%) or Shin 2026 (74.2% vs 82.1%). (4) Cost: subcutaneous injection discomfort 64.5% on maropitant versus 7.1% on saline (Shin).
Watch out: All vomiting evidence is against opioid premedication (hydromorphone in every trial) in mostly healthy elective-surgery dogs, observed for 20–30 minutes after premedication — it does not cover vomiting in recovery from non-opioid protocols, regurgitation as a standalone endpoint, or aspiration pneumonia, none of which any carded trial measured. Distinct from Shelf #168 (acute vomiting, maropitant vs metoclopramide): no record carded there is re-carded here, including Lorenzutti 2017 (PMID: 28042152), whose morphine-premedication comparison homes on that shelf.
Synthesis of Hay Kraus BL. PMID: 23082784; Johnson RA. PMID: 24330310; Hay Kraus BL. PMID: 24786163; Shin CW, Ambros B. PMID: 42208176; Jones CT, Fransson BA. PMID: 31355727. Registry IDs as on the individual cards.
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