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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

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

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 →

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

Educational reference only

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.

Educational reference only

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.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database