Maropitant (Cerenia, is an NK1 receptor antagonist that inhibits binding of substance P at the level of the emetic center in the brain, thereby controlling vomiting and nausea associated with a variety of stimuli. It is considered safe and effective and is commonly used in oncology patients. However, efficacy and safety studies unique to veterinary patients undergoing doxorubicin therapy, which can cause vomiting, diarrhea, inappetence, and nausea, have not been performed. This study investigated the effectiveness of maropitant as a nausea preventive when administered during doxorubicin treatment. A second objective was to examine whether maropitant administration intensified myelosuppression in dogs after doxorubicin therapy, as seen in a previous study.

Dogs with cancer (n = 59) were randomized to receive maropitant after the first doxorubicin dose and placebo after the second, or placebo after the first doxorubicin dose and maropitant after the second. Either maropitant (2 mg/kg) or placebo were administered PO for 5 days after doxorubicin treatment. Dogs that received maropitant with doxorubicin had significantly less vomiting or diarrhea the week after chemotherapy. The reduction in severity of diarrhea was an unexpected finding, possibly secondary to peripheral actions of substance P inhibition in peripheral smooth muscle contractility. No statistically significant differences were identified between maropitant and placebo for other gastrointestinal and bone marrow toxicoses. Study supported by Pfizer Animal Health’s 2008 oncology resident grant program

Commentary: Maropitant is anecdotally the most effective antinausea medication used in practice today, and is particularly useful given the ease of once daily oral administration. This study actually suggests a new protocol for administering doxorubicin that includes concurrent maropitant administration in order to improve quality of life (ie, prevention of vomiting and diarrhea).—Heather Troyer, DVM, Diplomate ABVP (Canine & Feline Practice)

Efficacy of maropitant in the prevention of delayed vomiting associated with administration of doxorubicin to dogs. Rau SE, Barber LG, Burgess KE. J VET INTERN MED 24:1452-1457, 2010.