Vomiting is one of the most common reasons dogs are presented for veterinary consultation.1 Most antiemetics (e.g. metoclopramide, diphen-hydramine, chlorpromazine, ondansetron, dolasetron) have been developed for use in people and are not approved for use in small animals.2 The recent introduction of maropitant citrate, which is from a novel class of antiemetics and is approved to prevent and treat acute vomiting in dogs with a variety of clinical conditions, is a major advance in managing these patients (Table 1).
Table 1 Indications and Dosages of Maropitant in Dogs*
Maropitant has been studied in dogs to treat acute vomiting associated with systemic disorders (e.g. gastroenteritis, acute pancreatitis, cholangitis) or infections (e.g. parvovirus infection except in young pups, leptospirosis) and a variety of other clinical disorders (e.g. uremia, renal failure, pyometra, diabetic ketoacidosis, hypercalcemia, adrenal insufficiency, intestinal obstruction, gastrointestinal neoplasia, linear foreign object, central nervous system disease, increased intracranial pressure, drug or toxic agent poisoning).3,4 It is also effective against vomiting due to motion sickness in dogs.5
Maropitant's efficacy and safety have been evaluated in randomized clinical trials for preventing vomiting due to motion sickness in dogs.5 Compared with a placebo, maropitant reduced vomiting by 86.1% or 76.5% when given two or 10 hours before travel, respectively.5,6 Comparatively, ondansetron is not effective against vomiting due to motion sickness.7 Maropitant is also effective in preventing and treating acute and delayed emesis in patients undergoing chemotherapy for cancer (e.g. cisplatin).8-10 Chemotherapeutic agents activate the chemoreceptor trigger zone by releasing various neurotransmitters, including substance P, both centrally and peripherally, to induce vomiting (see the sidebar titled "Maropitant's pharmacokinetics and pharmacology").3,8
DOSE AND ADMINISTRATION
To prevent acute vomiting in dogs, maropitant is given subcutaneously or orally before an anticipated emesis event and then once a day thereafter for up to five consecutive days (Table 1).3 To treat acute vomiting in dogs, 1 mg/kg maropitant is given subcutaneously once a day for up to five consecutive days.3 If you need to treat a patient after the five days, stop maropitant administration for two days, and then reinitiate therapy for up to another five days.3
To prevent motion sickness-induced vomiting, administer at least 8 mg/kg maropitant orally at least two hours before travel and once a day for up to two consecutive days.3 If longer treatment is needed, stop maropitant administration for three days, and then reinitiate therapy for up to another two days.3
Advise clients not to tightly wrap the tablets in fatty food such as cheese or meat since this may keep the tablets from dissolving and delay the effect.11 Dogs should not be fed one to two hours before receiving maropitant. It is also recommended to avoid inserting the tablets in hot dogs, sausage, or pocket-type treats.
Maropitant citrate injectable solution and tablets are used extra-label in cats for the same indications and at the same dosages as those in dogs.3