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Methadone

Full Mu-Opioid Agonist / NMDA Receptor Antagonist
Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
2 available
Interactions
3 documented
Formulations
3

Mechanism of action

Synthetic full mu-opioid agonist with additional NMDA receptor antagonist properties (prevents opioid-induced hyperalgesia and tolerance) and weak serotonin/norepinephrine reuptake inhibition. Excellent analgesic with unique anti-wind-up properties.

At a glance

Class
Full Mu-Opioid Agonist / NMDA Receptor Antagonist
Schedule
Controlled Substance
Storage
Store at room temperature; controlled substance secure storage

Dosing

🐕

Dog

Excellent perioperative analgesic with minimal histamine release (superior to mo
Dose
0.1–0.5 mg/kg
Route
IV, IM, SQ
Frequency
q4–6h (bolus); CRI
🐈

Cat

Excellent analgesic in cats
Dose
0.1–0.3 mg/kg
Route
IV, IM
Frequency
q4–6h

Formulations

💊

Other — 3

Strength
—
Strength
—
Strength
—

Storage

Store at room temperature; controlled substance secure storage

Safety

Monitoring parameters

Respiratory rateSpO2Pain scoresHeart rateECG (chronic use — QT interval)Level of sedation

Interactions

Major — 2

Selegiline (L-Deprenyl)
major
Methadone has weak serotonin reuptake inhibition + selegiline is MAO-B inhibitor: risk of serotonin syndrome.
Management: Avoid combination. If opioid needed with selegiline, use morphine or hydromorphone (no serotonergic activity).
Rifampicin
major
Rifampicin induces CYP3A4 and CYP2B6, dramatically increasing methadone metabolism and causing opioid withdrawal or loss of analgesia.
Management: Avoid combination. If unavoidable, increase methadone dose significantly and monitor pain scores closely.

Moderate — 1

Phenobarbital
moderate
Phenobarbital induces CYP enzymes, increasing methadone metabolism and reducing analgesic efficacy.
Management: May need to increase methadone dose or frequency. Monitor pain scores.

Brands

Other markets

Dolophine
Methadose

FAQs

Frequently asked questions

›What is Methadone?
Methadone is a full mu-opioid agonist / nmda receptor antagonist used in pets. Synthetic full mu-opioid agonist with additional NMDA receptor antagonist properties (prevents opioid-induced hyperalgesia and tolerance) and weak serotonin/norepinephrine reuptake inhibition. Excellent analgesic with unique anti-wind-up properties.
›What is Methadone used for in pets?
Methadone is used in veterinary medicine for: Excellent perioperative analgesic with minimal histamine release (superior to mo; Excellent analgesic in cats.
›What is the Methadone dose for dogs?
For dogs, Methadone is typically dosed as follows — Excellent perioperative analgesic with minimal histamine release (superior to mo: 0.1–0.5 mg/kg IV/IM/SQ q4–6h (bolus); CRI. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Methadone dose for cats?
For cats, Methadone is typically dosed as follows — Excellent analgesic in cats: 0.1–0.3 mg/kg IV/IM q4–6h. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›Does Methadone need a prescription?
Methadone is available over the counter. Even so, you should consult your veterinarian before giving any medication to your pet.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →