PREPARATIONS
Maropitant is FDA-approved for use only in dogs for subcutaneous injection or oral administration. It is available in the
United States as Cerenia (Pfizer Animal Health) and is supplied as a tablet and an injectable solution (20-ml amber glass
vials). The tablets contain 16, 24, 60, or 160 mg maropitant citrate. Each milliliter of solution contains 10 mg maropitant
citrate, 63 mg sulfobutylether-beta-cyclodextrin (SBECD), and 3.3 mg metacresol as a preservative. Cyclodextrins improve water
solubility and stability and reduce the toxicity of the molecules.12 Dogs receiving SBECD orally may experience gastrointestinal effects such as soft feces or diarrhea. These effects are reversible
when treatment is withdrawn.13
TOXICITY
Maropitant has a low acute toxicity: the oral LD50 (free base) in rats is > 2,000 mg/kg.14 Maropitant is well-tolerated in healthy dogs receiving doses of up to three times the recommended oral dose of 8 mg/kg or
for three times longer than the proposed maximum duration of treatment.3,12 In cats, maropitant is also well-tolerated at doses up to 5 mg/kg.15
Maropitant is not teratogenic in rats, but it has not been evaluated in pregnant, breeding, or lactating dogs.14 Do not administer maropitant in dogs younger than 16 weeks because bone marrow hypoplasia has been reported in puppies younger
than 11 weeks.12 Also administer it with caution in dogs with hepatic dysfunction.3
ADVERSE REACTIONS
The most common adverse reactions noted during high-dose (> 8 mg/kg) clinical studies in dogs included hypersalivation, diarrhea,
bloody stools, drooling, retching, lethargy, loss of appetite, muscle tremors, and flatulence.12,16 Swelling or pain at the injection site has been reported after subcutaneous administration.3,12 At high dosages, maropitant can interact with cardiac calcium channels: at a dosage of 20 mg/kg given orally once a day
for 93 days, electrocardiographic changes (slight increases in P-R interval, P-wave duration, and QRS amplitude) were noted.3,17 According to the Canadian product label, use maropitant with caution in dogs with bradycardia or underlying heart disease
since maropitant may increase the risk of arrhythmias.12
HANDLING PRECAUTIONS
Topical exposure may elicit localized allergic skin reactions in some people. Repeated or prolonged exposure may lead to skin
sensitization.12 Direct exposure of the skin or eyes may cause allergic reactions, so avoid drug contact with the skin and eyes and wear
impervious gloves during administration.
ENVIRONMENTAL ISSUES
Maropitant is degraded slowly, so avoid releasing it into the environment.14 Maropitant is also highly toxic to aquatic organisms,14 so do not allow the product to contaminate ponds, waterways, or ditches.
STORAGE AND STABILITY
Store maropitant injectable solution at a controlled room temperature of 68 to 77 F (20 to 25 C), and protect it from light.3 The injection product label states the drug should be used within 28 days of first vial puncture in accordance with FDA
requirements. Maropitant tablets are packaged in foil to protect them from moisture. Tablets removed from the blister pack
and halved do not lose potency within 48 hours.3
Lotfi El Bahri, DVM, MSc, PhD
Department of Pharmacology and Toxicology
École Nationale de Médecine Vétérinaire
2020 Sidi-Thabet, Tunisia
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