VETINUITY
Why choose methadone over hydromorphone?
Methadone rarely causes vomiting and adds NMDA receptor antagonism, which helps in patients where emesis is unwanted, such as those with a GDV, raised intracranial pressure or an ocular injury.
● ANSWER
Sourced & dated
What is the methadone dose for dogs and cats?
Methadone is dosed at 0.2-0.5 mg/kg IV, IM or SC every 4-6 hours in dogs and 0.2-0.3 mg/kg IV or IM every 4-6 hours in cats, and rarely causes vomiting.
● VETINUITY METHADONE DOSE CALCULATOR
Vetinuity methadone dose calculator
Methadone 10 mg/mL. Start low in sick or old patients and titrate to effect.
● WHAT'S DOCUMENTED
Per Vetinuity’s methadone dose table, dogs get 0.2-0.5 mg/kg IV, IM or SC every 4 to 6 hours and cats get 0.2-0.3 mg/kg IV or IM every 4 to 6 hours, with the low end for premedication combined with a sedative and the high end for severe pain. The Vetinuity methadone dose calculator above gives the milligrams and the volume of 10 mg/mL stock.
Dose table
| Indication | Dog | Cat | Route and frequency |
|---|---|---|---|
| Premedication with acepromazine or dexmedetomidine | 0.2-0.3 mg/kg | 0.2-0.3 mg/kg | IM or IV once |
| Moderate to severe pain | 0.3-0.5 mg/kg | 0.2-0.3 mg/kg | IV, IM or SC q4-6h |
| Intraoperative top-up | 0.1-0.2 mg/kg | 0.1 mg/kg | IV to effect |
What sets methadone apart
Methadone is a full mu agonist like hydromorphone, but it also blocks NMDA receptors, which may help with wind-up and hyperalgesia after major surgery. It seldom triggers vomiting, a real advantage before induction in a dog with a GDV, a corneal laceration or head trauma, where retching is dangerous. Dogs often pant and may show bradycardia; cats can show mydriasis and mild excitement at higher doses. In cats, Ferreira and colleagues found antinociception after IV dosing and measurable plasma levels after oral transmucosal dosing.
Cautions
Respiratory depression is dose-related and matters most in brachycephalic dogs and in patients with head trauma, where a rise in PaCO2 raises intracranial pressure. Repeat doses accumulate in hepatic disease, so lengthen the interval. Reverse with naloxone if needed, remembering that the analgesia goes too. Methadone is Schedule II in the US.
Duration and redosing
A single IM dose usually covers 4 to 6 hours in dogs and a little longer in many cats. Reassess with a pain score before each repeat rather than dosing on the clock, and switch to a CRI of a shorter-acting full agonist when a patient needs repeated doses every few hours. Before discharge, plan the step-down to an oral or transmucosal option, since methadone does not go home.
Vetinuity, built by emergency veterinarian Brian Toncray, DVM, ties this table to the GDV stabilization and cesarean pages, two cases where a non-emetic full agonist earns its place. Partial agonist alternative: buprenorphine. Common sedative partner: acepromazine.
● SOURCES
- 1. Ferreira TH, Rezende ML, Mama KR, et al. Plasma concentrations and behavioral, antinociceptive, and physiologic effects of methadone after intravenous and oral transmucosal administration in cats. Am J Vet Res. 2011;72(6):764-771. PMID 21627522. Abstract. Checked 2026-10-26.
- 2. Grubb T, Sager J, Gaynor JS, et al. 2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2020;56(2):59-82. PMID 32078360. Premedication and analgesia tables. Checked 2026-10-26.
● RELATED ANSWERS
- GDV in Dogs: Emergency Stabilization Steps
Vetinuity's GDV table: two large forelimb catheters, crystalloid boluses of 20 mL/kg, gastric decompression by trocar or tube, a full mu opioid and lidocaine 2 mg/kg IV then 50 mcg/kg/min.
- Hydromorphone Dose for Dogs and Cats
Hydromorphone is dosed at 0.05-0.1 mg/kg IV, IM or SC every 4-6 hours in dogs and 0.025-0.05 mg/kg IV or IM every 4-6 hours in cats, or as a 0.01-0.03 mg/kg/h CRI in dogs.
- Buprenorphine Dose for Dogs and Cats (Simbadol)
Buprenorphine is dosed at 0.01-0.02 mg/kg IV or IM every 6-8 hours in dogs and 0.01-0.03 mg/kg IV, IM or oral transmucosal every 6-8 hours in cats, with the 1.8 mg/mL Simbadol formulation at 0.24 mg/kg SC once daily in cats only.
- Naloxone Dose for Dogs and Cats
Naloxone is dosed at 0.01-0.04 mg/kg IV, IM or SC in dogs and cats to reverse opioids, titrated in small diluted increments when only partial reversal is wanted, and repeated because it wears off in 30-60 minutes.
- Acepromazine Dose for Dogs and Cats
Injectable acepromazine is dosed at 0.01-0.05 mg/kg IV, IM or SC in dogs (commonly capped at 1-3 mg total) and 0.03-0.05 mg/kg IM or SC in cats, combined with an opioid because it gives no analgesia.
- Anesthesia for Cesarean Section in Dogs
Randomized trials comparing alfaxalone with propofol for canine cesarean induction: better neonatal Apgar scores with alfaxalone, similar puppy survival.
● FAQ
Is methadone given by mouth to dogs?
No. Oral methadone has very low bioavailability in dogs, so it is used by injection.
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