What is the correct maropitant dose for dogs versus cats and can it be used for motion sickness and postoperative nausea?

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Maropitant dosing differs by indication and species, with dogs requiring higher doses for motion sickness than for acute vomiting, and cats dosed by total tablet weight rather than a per-kg injectable equivalent. For acute vomiting in dogs, the oral dose is 2 mg/kg PO q24h; in dogs actively vomiting, the injectable formulation at 1 mg/kg SC or IV q24h is recommended first to ensure the full dose is delivered, after which oral maropitant at 2 mg/kg q24h can be used interchangeably for up to 5 days total.2 Dogs 2–7 months of age are limited to 5 consecutive days of treatment.2 For motion sickness in dogs, the dose is 8 mg/kg PO q24h for up to 2 consecutive days, administered at least 2 hours before travel with a small amount of food.2 At this dose, 93% of motion-sickness-prone dogs did not vomit during a one-hour car journey, compared with 48% of placebo-treated dogs.10 The injectable formulation is not interchangeable with tablets for the motion sickness indication.2 In cats, the published antiemetic dose for prevention of opioid-induced emesis is 8 mg total dose PO (mean 2.9 mg/kg), administered 2–2.5 hours before morphine and dexmedetomidine.12 At this dose and interval, retching was reduced from 36% to 13% and emesis from 32% to 13%; sialorrhea and lip licking were not reduced, indicating maropitant suppresses vomiting but not nausea in cats.12 When maropitant is given SC to cats within 30 minutes of an emetogenic opioid, peak plasma concentrations may not be achieved before the emetogenic agent acts, reducing efficacy — a lead time of at least 30–60 minutes is required.3 For perioperative use in dogs, maropitant must be given at least 15 minutes before an opioid to significantly reduce vomiting, and at least 60 minutes before to also significantly reduce signs of nausea.5 After SC administration in dogs, peak plasma concentration is reached within approximately 45 minutes of a 1 mg/kg dose.1 Maropitant reduces overall intraoperative isoflurane requirements — mean