Butorphanol
Butorphanol tartrate
Also known as: Stadol · Torbutrol · Torbugesic · Dolorex · Equanol · Alvegesic · Butomidor · Torphasol · levo-BC-2627 · butorphanol tartrate
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Reviewed non-calculator evidenceReviewed non-calculator evidence (5)
Evidence only — not for automatic calculation
Chelonians/minimal sedation
TABLE 127.5. Agent: Butorphanol. Dosage: 0.2 mg/kg IM118,275. Species/Comments: Chelonians/minimal sedation.
Evidence only — not for automatic calculation
Most species/sedation; preanesthetic
TABLE 127.5. Agent: Butorphanol. Dosage: 0.4–1 mg/kg SC, IM295. Species/Comments: Most species/sedation; preanesthetic.
Evidence only — not for automatic calculation
Most species/preanesthetic
TABLE 127.5. Agent: Butorphanol. Dosage: 0.5–2 mg/kg IM, or 0.2–0.5 mg/kg IV, IO23. Species/Comments: Most species/preanesthetic.
Evidence only — not for automatic calculation
Butorphanol combinations follow; see ketamine for combinations; inadequate for analgesia
TABLE 127.5. Agent: Butorphanol. Dosage: —. Species/Comments: Butorphanol combinations follow; see ketamine for combinations; inadequate for analgesia.
Evidence only — not for automatic calculation
Lizards/administer 30 min before isoflurane for smoother, shorter induction
TABLE 127.5. Agent: Butorphanol. Dosage: 1–1.5 mg/kg SC, IM295. Species/Comments: Lizards/administer 30 min before isoflurane for smoother, shorter induction.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Butorphanol is a synthetic opioid partial agonist widely used in veterinary medicine across multiple species.
- Analgesia: Provides mild to moderate visceral analgesia. Due to its "ceiling effect," higher doses do not increase pain relief, making it unsuitable for severe pain (e.g., major orthopedic procedures).
- Antitussive: Highly effective for suppressing chronic non-productive coughs (e.g., infectious tracheobronchitis, tracheal collapse) in dogs.
- Reversal Agent: Uniquely useful for reversing the profound respiratory and CNS depression of pure mu-agonists (like fentanyl, methadone, or morphine) while still maintaining a degree of kappa-mediated analgesia.
- Sedation: Frequently combined with alpha-2 agonists (like dexmedetomidine or xylazine) and benzodiazepines for synergistic sedation and chemical restraint.
Clinical Pearl: While butorphanol is an excellent antitussive and mild sedative in small animals, its very short duration of action (often <1 hour for analgesia in dogs) limits its utility as a primary analgesic. Conversely, it is a highly effective and commonly used visceral analgesic in horses (e.g., for colic).
Mechanism of action
Butorphanol exerts its effects by interacting with specific opioid receptors in the central nervous system:
- Kappa (κ) and Sigma (σ) Agonist: Activation of κ-receptors in the limbic system and spinal cord provides visceral analgesia and sedation.
- Mu (μ) Antagonist: Competitively binds to and blocks μ-receptors. This antagonism is responsible for its ability to reverse pure μ-agonist drugs and is the reason for its analgesic "ceiling effect."
- Antitussive Mechanism: Directly suppresses the medullary cough center, elevating the threshold to stimuli (like CO2) without depressing respiratory center sensitivity as profoundly as pure agonists.
- Cellular Pathway: Binds to κ-receptors → inhibits adenylate cyclase → decreases intracellular cAMP → closes voltage-gated calcium channels and opens potassium channels → hyperpolarization and reduced neuronal excitability.
Safety & warnings
Contraindications
- Known hypersensitivity to butorphanol
- Lower respiratory tract conditions with copious mucous production (suppressing cough prevents clearance)
- Caution in patients with head trauma, increased CSF pressure, or severe CNS dysfunction (e.g., coma)
- Caution in severe liver disease, renal insufficiency, hypothyroidism, or Addison's disease
- Caution in dogs with heartworm disease (safety not established)
Adverse effects
- Sedation and ataxia
- Anorexia or diarrhea (rare in small animals)
- Respiratory depression (mild compared to pure agonists)
- CNS excitement, head tossing, and increased ambulation (especially in horses at high doses or rapid IV administration)
- Decreased gastrointestinal motility and potential ileus (horses)
- Nystagmus, salivation, seizures, and hyperthermia (at massive overdoses in horses)
Precautions
MDR1 (ABCB1) Mutation Warning: Dogs with the MDR1 mutation (e.g., Collies, Australian Shepherds) may develop pronounced and prolonged sedation. Reduce the dose by 25% in heterozygous dogs and by 30-50% in homozygous mutant dogs.
Geriatric/Debilitated Patients: Use with caution and consider dose reductions.
Hepatic/Renal Impairment: The manufacturer advises against use in dogs with a history of liver disease. Use cautiously in renal insufficiency.
Pregnancy/Nursing: Category C (human). Safe for use if used cautiously in dogs/cats, but manufacturer does not recommend use in pregnant bitches, foals, weanlings, or breeding horses.
Drug interactions
May cause increased CNS or respiratory depression; dosage may need to be decreased.
Could potentially decrease the metabolism of butorphanol, prolonging its effects.
Butorphanol may antagonize analgesic effects, but will also reverse sedative and respiratory depressant effects.
May cause increased conjunctival changes when used concurrently.
Could potentially decrease the metabolism of butorphanol.
Reduces the doses of other drugs required for induction and maintenance of anaesthesia
Addition of butorphanol will reduce analgesia produced from the full mu agonist; combination is not recommended for analgesia
Synergistic sedation
Synergistic sedation and analgesia
Butorphanol's mu-antagonist properties may block or partially reverse the analgesic effects of full mu-agonists. Higher doses of full mu-agonists may be required.
Monitoring
- Analgesic and/or antitussive efficacy
- Respiratory rate and depth
- Appetite and bowel function
- CNS effects (sedation vs. excitement)
Pharmacokinetics
Half-life
Absorption
Completely absorbed in the gut when administered orally, but due to a high first-pass effect, only about 16% (1/6th) reaches systemic circulation. Completely absorbed following IM administration.
Distribution
Well distributed. Highest levels found in liver, kidneys, and intestine. Approximately 80% bound to plasma proteins. Crosses the placenta (neonatal levels roughly equivalent to maternal) and distributes into maternal milk.
Metabolism
Metabolized in the liver, primarily by hydroxylation, as well as N-dealkylation and conjugation. Metabolites do not exhibit analgesic activity.
Elimination
Metabolites and parent compound are mainly excreted into the urine (only 5% unchanged). 11-14% is excreted into the bile and eliminated in feces.
Overdose
Acute life-threatening overdoses are unlikely (LD50 in dogs is 50 mg/kg). However, because veterinary injection comes in two highly different strengths (0.5 mg/mL and 10 mg/mL), inadvertent overdoses can occur in small animals.
Clinical Signs: CNS effects (profound sedation or excitement), cardiovascular changes, and respiratory depression.
Treatment:
- Administer intravenous naloxone immediately to reverse opioid effects.
- Provide supportive measures: IV fluids, oxygen therapy, vasopressors, and mechanical ventilation if required.
- If seizures occur and persist, use diazepam for control.
Available products
Formulations
- Veterinary Injection: 0.5 mg/mL, 2 mg/mL, 10 mg/mL
- Veterinary Tablets: 1 mg, 5 mg, 10 mg
- Human Injection: 1 mg/mL, 2 mg/mL
- Human Nasal Spray: 10 mg/mL
Veterinary
- Butorphanol Tartrate Injection: 0.5 mg/mL (Torbutrol)
- Butorphanol Tartrate Injection: 2 mg/mL (Torbugesic-SA)
- Butorphanol Tartrate Injection: 10 mg/mL (Torbugesic, Dolorex, Butorject, Torphaject, Equanol)
- Butorphanol Tartrate Tablets: 1 mg, 5 mg, and 10 mg (Torbutrol)
Human-labeled
- Butorphanol Tartrate Injection: 1 mg/mL, 2 mg/mL (Stadol)
- Butorphanol Nasal Spray: 10 mg/mL
Regulatory status
Subject to specific member state controlled drug regulations.
Classified as POM-V (Prescription Only Medicine - Veterinarian).
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
The injectable product should be stored out of bright light and at room temperature; avoid freezing.
Client information
What is this medication? Butorphanol is a medication used to relieve coughing, provide mild pain relief, or act as a sedative before veterinary procedures.
What should I expect?
- Your pet will likely become sleepy or slightly uncoordinated (wobbly). This is normal, but you should keep them in a safe, quiet environment (e.g., avoid stairs) until the effects wear off.
- If prescribed for a cough, you should notice a significant decrease in coughing spells.
Important Warnings:
- Do not give more than prescribed. Giving too much will not increase pain relief but can increase side effects.
- If your pet's cough changes from a "dry, hacking" cough to a "wet, productive" cough, contact your veterinarian. Suppressing a wet cough can trap mucus in the lungs.
- Report any significant changes in behavior, loss of appetite, or severe constipation/diarrhea to your veterinarian.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.