Methocarbamol: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Robaxin, Robinax

Species with doses

Dogs, Cats and Horses

General dose range

20–45 mg/kg PO q8h (titrate to effect) — check the species tables for the indication

Routes

IV, PO

Last reviewed

1 October 2026

Indications

• Tremorgenic toxicoses — permethrin (cats), metaldehyde, tremorgenic mycotoxins, strychnine, pyrethroids
• Acute muscle spasm / muscle pain (e.g. with intervertebral disc disease)
• Adjunct relaxation in tetanus (muscle rigidity)

Methocarbamol dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Tremorgenic toxicosis (metaldehyde, mycotoxin): Papich 5e and Plumb’s p.805 (label): severe conditions 55–220 mg/kg IV — half rapidly, the rest to effect — maximum 330 mg/kg/day; mycotoxin tremors no faster than 2 mL/min (Schell 2000); caffeine/guarana 50–220 mg/kg slowly IV.
• Muscle spasm / IVDD pain (oral): Papich 5e (label): 44 mg/kg q8h PO, then 22–44 mg/kg q8h, not beyond 14–21 days. Plumb’s p.805: label 132 mg/kg/day divided q8–12h, then 61–132 mg/kg/day; IVDD muscle relaxation 15–20 mg/kg PO three times daily (Morgan). Stop if no response in 5 days.

Cats

• Permethrin / tremorgenic toxicosis: Papich 5e and Plumb’s p.805 (label): moderate conditions 44 mg/kg IV; severe (strychnine, tetanus) 55–220 mg/kg IV — give half rapidly, then the rest to effect; do not exceed 330 mg/kg/day. Permethrin toxicity: 50–150 mg/kg IV, first half over 5–10 min, then to effect; can be given as a CRI over 24 h in severe cases (Boag 2009). Bathe/decontaminate and support.

Horses

• Muscle spasm / tying-up adjunct: Papich 5e and Plumb’s p.805 (label): moderate conditions 4.4–22 mg/kg IV to effect (q8h); severe 22–55 mg/kg IV; acute rhabdomyolysis 15–25 mg/kg by slow IV infusion, up to four times daily (Hanson 1999). Oral: 2–3 times the IV dose. Above 30 mg/kg IV causes depression. ARCI Class 4.

Contraindications

Renal impairment (the IV formulation's polyethylene glycol vehicle is a concern; oral generally fine). Do not exceed the maximum daily dose (~330 mg/kg/day). Rapid IV bolus (CNS depression, recumbency). Known hypersensitivity. Ensure airway protection in heavily affected toxicosis patients.

Species-specific warnings

Cats: A frontline drug for permethrin toxicosis in cats (from misapplied dog spot-ons) — titrate IV to control tremors and decontaminate the cat; this is an emergency.

Adverse effects

• Sedation, weakness, ataxia, recumbency (dose-related)
• Hypersalivation, vomiting
• Excessive CNS depression at high dose
• Brown/green-brown urine discolouration (harmless)

Drug interactions

• Other CNS depressants (opioids, benzodiazepines, anaesthetics): additive sedation/respiratory depression
• No major specific pharmacokinetic interactions of note

Pregnancy and lactation

Limited data; used when needed for serious toxicosis (where maternal benefit is clear). Crosses into milk.

Monitoring

• Tremor control vs over-sedation (titrate carefully in toxicoses)
• Respiratory status in heavily affected patients (airway protection)
• Temperature (hyperthermia from tremors; hypothermia from over-relaxation)
• Total daily dose (do not exceed ~330 mg/kg/day)

Toxicity and overdose

Overdose causes excessive CNS depression — profound sedation, ataxia, recumbency, weakness and, at very high doses, respiratory depression. The IV vehicle can be problematic in renal impairment. Generally a wide margin and reversible with discontinuation/support.

Management: No specific antidote. Support airway/ventilation if severely depressed, IV fluids, nursing care (thermoregulation, recumbency care); effects resolve as the drug is metabolised. Reduce/stop dosing and monitor until ambulatory.

Clinical pearls

• The muscle-relaxant of choice for tremorgenic poisonings — titrate IV to stop the tremors while keeping the patient breathing
• In permethrin-toxic cats, combine methocarbamol with decontamination (bathe off the product), thermoregulation and supportive care
• Give IV slowly and to effect; the goal is tremor control, not flat recumbency
• Respect the daily maximum (~330 mg/kg/day) and protect the airway in obtunded patients
• Harmless brown urine discolouration can alarm owners — reassure them

Mechanism of action

A centrally acting muscle relaxant that depresses polysynaptic reflex transmission in the spinal cord and brainstem (likely via general CNS depression rather than a specific receptor), reducing skeletal-muscle hyperactivity and tremor. It does not act at the neuromuscular junction or directly on muscle, and produces relaxation/sedation without true anaesthesia or analgesia.

Formulations and products

• 500 mg tablet
• 750 mg tablet
• Injection 100 mg/mL
• Robinax — 500 mg tablet; 100 mg/mL injection, Tablet / injection (human-label)
• Robaxin — 500 / 750 mg tablet, Tablet (human-label)

Storage

Tablets: 15–30 °C, dry. Injection: 15–30 °C, protect from light; do not refrigerate (precipitation).

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other hormones, emergency drugs, supplements and other drugs

• Loratadine
• Megestrol Acetate
• Metformin
• Methimazole
• Methylcobalamin (Active B12)
• Methylene Blue
• Mitotane (o,p'-DDD)
• Mycophenolate Mofetil

Frequently asked questions