Maropitant Citrate — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	2 mg/kg	q24h	Duration: Up to 5 days (for acute vomiting); for motion sickness, administer 2 mg/kg at least 1-2 hours before travel Notes: For motion sickness, use the tablet formulation; for acute vomiting, can use injectable or oral. May be used for up to 5 days for chemotherapy-induced vomiting.
Dog	IV	1 mg/kg	q24h	Duration: Up to 5 days Notes: Administer as a slow intravenous injection or as a subcutaneous injection. For prevention of postoperative vomiting, administer at induction of anesthesia.
Cat	PO	2 mg/kg	q24h	Duration: Up to 5 days Notes: For motion sickness, administer at least 1-2 hours before travel. Tablets are scored for dosing.
Cat	SC	1 mg/kg	q24h	Duration: Up to 5 days Notes: Subcutaneous injection is approved in cats. For acute vomiting, may be used for up to 5 days.
Horse	IV	0.5-1 mg/kg	q24h	Duration: As needed Notes: Limited data; use with caution. May be used for nausea associated with colic or other conditions.
Cattle	IV	0.5-1 mg/kg	q24h	Duration: As needed Notes: Off-label use; not approved for food animals. Withdrawal times must be observed.
Rabbit	PO	1-2 mg/kg	q24h	Duration: As needed Notes: Off-label use; limited safety data.

Clinical Indications & Species Uses

General Indications

Prevention and treatment of vomiting in dogs and cats

Dog (Canine)

Prevention and treatment of acute vomiting
Prevention of vomiting due to motion sickness
Prevention of chemotherapy-induced nausea and vomiting
Prevention of postoperative vomiting

Cat (Feline)

Prevention and treatment of acute vomiting
Prevention of vomiting due to motion sickness (off-label in some regions)
Prevention of chemotherapy-induced nausea and vomiting

Pharmacology & Mechanism of Action

Drug Class: Antiemetic | Pharmacological Group: Neurokinin-1 (NK1) receptor antagonist

Mechanism of Action: Maropitant is a selective antagonist of the neurokinin-1 (NK1) receptor, which is the primary receptor for substance P. Substance P is a neuropeptide involved in the transmission of emetic signals from the gastrointestinal tract and central nervous system. By blocking NK1 receptors in the central pattern generator (vomiting center) and the chemoreceptor trigger zone (CRTZ), maropitant prevents both centrally and peripherally mediated vomiting. It also has some anti-inflammatory properties by inhibiting substance P-mediated neurogenic inflammation.

Pharmacodynamics: Maropitant inhibits the emetic response to various stimuli, including motion sickness, chemotherapy, and toxins. It has a long duration of action, providing antiemetic coverage for up to 24 hours after a single dose. It does not affect gastrointestinal motility significantly. In dogs, it has been shown to reduce the incidence of vomiting associated with cisplatin and apomorphine. In cats, it is effective against xylazine-induced vomiting. The drug also exhibits some analgesic effects in visceral pain models.

⚡ Pharmacokinetics Summary

Absorption: Maropitant is well absorbed after oral administration in dogs and cats, with a bioavailability of approximately 37% in dogs (due to first-pass metabolism) and 50% in cats. Absorption is not significantly affected by food. The onset of action after oral administration is within 1-2 hours, while intravenous administration provides rapid effect.

Distribution: Maropitant has a large volume of distribution, indicating extensive tissue distribution. It crosses the blood-brain barrier to reach central NK1 receptors. It is highly protein-bound (greater than 99%) in plasma. It is distributed into milk and crosses the placenta.

Metabolism: Maropitant is extensively metabolized in the liver, primarily by cytochrome P450 enzymes (CYP3A4 in dogs, and similar enzymes in other species). It undergoes oxidative metabolism and conjugation. The metabolites are less active than the parent compound.

Excretion: The drug and its metabolites are excreted primarily in the feces (approximately 70%) and to a lesser extent in urine (approximately 20%). In dogs, the elimination half-life is approximately 5-8 hours after intravenous administration and 9-13 hours after oral administration. In cats, the half-life is approximately 13-16 hours.

Half-Life: Dog: 5-8 hours (IV), 9-13 hours (oral); Cat: 13-16 hours; Horse: approximately 2-4 hours (IV); Cattle: approximately 3-5 hours (IV)

Bioavailability: Dog: ~37% (oral); Cat: ~50% (oral); Horse: ~8% (oral)

Protein Binding: >99% in dogs and cats

Available Formulations & Strengths

Oral Tablet 16 mg, 24 mg, 60 mg, 160 mg (PO)

Injectable Solution 10 mg/mL (50 mL vial) (IV, SC)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to maropitant or any component of the formulation
Use in animals with gastrointestinal obstruction or suspected toxicity (e.g., ingestion of toxins) as it may mask signs
Use in pregnant or lactating animals unless the benefits outweigh risks (safety not fully established)

Warnings & Clinical Precautions:

Use with caution in animals with hepatic disease, as maropitant is metabolized in the liver
Use with caution in animals with cardiovascular disease, as it may cause transient hypotension when given IV
In dogs, the injectable formulation is approved for subcutaneous use; intravenous use should be slow
In cats, the injectable formulation is approved for subcutaneous use only
Do not use in animals with known hypersensitivity to the drug
Safety in puppies and kittens less than 8 weeks of age has not been established
May cause pain at injection site; administer subcutaneously with care
For motion sickness, administer at least 1-2 hours before travel for optimal effect

Adverse Effects & Reactions

Common:

Pain at injection site
Vocalization (in cats)
Hypersalivation
Lethargy
Decreased appetite
Diarrhea

Serious / Severe:

Anaphylaxis (rare)
Cardiac arrhythmias (rare, with rapid IV administration)
Hepatotoxicity (rare, with prolonged use)

Rare:

Ataxia
Tremors
Seizures
Hypotension

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
CYP3A4 inhibitors (e.g., ketoconazole, itraconazole)	May increase maropitant plasma concentrations, potentially increasing risk of adverse effects	Moderate
CYP3A4 inducers (e.g., phenobarbital, rifampin)	May decrease maropitant efficacy by increasing its metabolism	Moderate
Other antiemetics (e.g., metoclopramide, ondansetron)	Additive antiemetic effects; may be used together in refractory cases, but monitor for excessive sedation	Mild
Nonsteroidal anti-inflammatory drugs (NSAIDs)	No significant interaction reported, but concurrent use may increase risk of gastrointestinal ulceration due to stress of vomiting	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Vomiting
Diarrhea
Lethargy
Ataxia
Tremors
Seizures (in severe cases)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce vomiting if recent oral ingestion and animal is conscious (unless contraindicated). Administer activated charcoal to reduce absorption. Provide intravenous fluids and electrolyte support. Monitor for neurological signs and treat seizures with diazepam or barbiturates if necessary. In cases of severe overdose, consider hospitalization and intensive care.

Food Animal Withdrawal Times

Maropitant is not approved for use in food-producing animals. If used off-label in cattle or other food animals, a withdrawal period of at least 30 days for meat and 7 days for milk is recommended, but local regulations should be consulted. No established withdrawal times for eggs in poultry.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20°C to 25°C (68°F to 77°F), excursions permitted between 15°C and 30°C (59°F and 86°F).

Handling & Special Conditions: Protect from freezing. Keep the injectable solution in the original carton to protect from light. Store tablets in a dry place.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved by the FDA for use in dogs (Cerenia®) and cats (Cerenia®) for the prevention and treatment of vomiting.

Extra-Label (Off-Label) Use: In the United States, maropitant is approved for use in dogs and cats. Extra-label use in other species is permitted under the Animal Medicinal Drug Use Clarification Act (AMDUCA) provided there is a valid veterinarian-client-patient relationship, and appropriate withdrawal times are observed for food animals.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Maropitant is a highly effective antiemetic for dogs and cats, with a broad spectrum of activity against both central and peripheral emetic stimuli. It is particularly useful for motion sickness, chemotherapy-induced vomiting, and acute vomiting of various etiologies. The drug is well tolerated, with minimal adverse effects. For motion sickness, it should be administered at least 1-2 hours before travel. In cats, the injectable formulation is approved for subcutaneous use only. In dogs, the injectable can be given IV or SC. Maropitant may also have analgesic properties, making it useful in visceral pain conditions. It is important to consider the underlying cause of vomiting, as maropitant may mask clinical signs of serious conditions such as gastrointestinal obstruction or toxin ingestion. Use with caution in animals with hepatic impairment. For food animals, extra-label use requires careful consideration of withdrawal times.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)