Maropitant Citrate

(for veterinary information only)


AVAILABLE IN           
16 mg, 24 mg, 60 mg, & 160 mg
and as INJECTABLE        


While strong nausea-controlling drugs in injectable form have been available for dogs for some time, oral medications have been lacking. Until recently, efforts were largely confined to the oral use of metoclopramide (which is rather short acting) and meclizine (which is not approved for use in dogs). In 2008, Pfizer released maropitant citrate, a strong anti-nauseal medication for dogs that could be given once a day. Maropitant has since been approved for cats as well.

Vomiting occurs when the vomit center of the brain stem is stimulated. It may be stimulated a number of ways: via the brain (as in motion sickness or through emotional input), via the chemoreceptor trigger zone in the brain stem (as when nauseating toxins are detected in the bloodstream), directly (as in dietary indescretion), or a combination of any of the above. An important molecular step in initiating vomiting, involves the binding of a material called “substance P” to a structure called the “NK-1 receptor.” This lock and key binding occurs in both the vomit center and in the chemoreceptor trigger zone. Maropitant citrate mimics the structure of substance P and binds the NK-1 receptors so that they cannot bind substance P thus making stimulation of the vomit center extremely difficult.


Maropitant is used once a day in dogs to control nausea. It can be given as a shot or as a tablet. The dose is higher for motion sickness versus for treatment of disease-related nausea. For the former, maropitant can be given two days in a row and for the latter for 5 days in a row.


Side effects are uncommon with the use of this medication but the most commonly noted side effects were: drooling, drowsiness, diarrhea, and appetite loss.


The risk of experiencing the above maropitant side effects is increased when maropitant is combined with other drugs that are highly blood protein bound in the circulation. Common drugs that meet this criterion are: Phenobarbital, non-steroidal anti-inflammatory drugs, and thyroid hormone supplements.


  • Note that the dosage recommended for a one time control of motion sickness is much higher than that for longer term nausea relief (as in the treatment of a disease).
  • Maropitant is approved for puppies over 8 weeks of age and cats at least 16 weeks of age.
  • Maropitant is for use in 5 day courses. After 5 days, the pet should come off maropitant for the 6th day but can start a new 5 day course on the 7th day. For motion sickness, maropitant can be given two days in a row.
  • Do not give this medication wrapped in a treat that may upset your pet’s stomach. Minimize fatty treats as they work against the effectiveness of the medication.
  • Maropitant may not be appropriate for pets with liver disease.
  • Maropitant has not been evaluated in pregnant or nursing animals.

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Page posted: 2/7/2012