Butorphanol Tartrate — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	IV, IM, SC	0.2-0.6 mg/kg (analgesia); 0.1-0.2 mg/kg (antitussive)	q2-4h as needed	Duration: As needed for pain control Notes: For preanesthetic: 0.1-0.2 mg/kg IV/IM/SC. For sedation, combine with acepromazine (0.05 mg/kg) or dexmedetomidine (0.005 mg/kg).
Cat	IV, IM, SC	0.2-0.8 mg/kg (analgesia); 0.1-0.2 mg/kg (preanesthetic)	q2-4h as needed	Duration: As needed for pain control Notes: Higher doses may be needed in cats due to shorter duration of action. For sedation, combine with dexmedetomidine (0.01 mg/kg) or acepromazine (0.05 mg/kg).
Horse	IV	0.02-0.1 mg/kg (analgesia for colic)	q4-6h as needed	Duration: As needed Notes: May cause ataxia at higher doses. Use with caution in horses with hepatic or renal impairment.
Cattle	IV, IM, SC	0.05-0.1 mg/kg (analgesia)	q4-6h as needed	Duration: As needed Notes: Not approved for food animals in the US; extra-label use requires withdrawal time estimation.
Small Ruminants (sheep, goats)	IV, IM, SC	0.1-0.2 mg/kg (analgesia)	q4-6h as needed	Duration: As needed Notes: Limited data; use with caution.
Rabbit	IV, IM, SC	0.1-0.5 mg/kg (analgesia)	q2-4h as needed	Duration: As needed Notes: May cause sedation. Monitor for respiratory depression.
Bird (psittacines, raptors)	IM	1-2 mg/kg (analgesia)	q2-4h as needed	Duration: As needed Notes: Limited studies; dose may vary by species.

Clinical Indications & Species Uses

General Indications

Management of moderate to severe pain
Preanesthetic medication
Antitussive (dogs)

Dog (Canine)

Relief of moderate to severe pain (visceral pain, postoperative pain)
Preanesthetic medication
Antitussive (nonproductive cough)
Sedation in combination with other agents (e.g., acepromazine, dexmedetomidine)

Cat (Feline)

Relief of moderate to severe pain (visceral pain, postoperative pain)
Preanesthetic medication
Sedation in combination with other agents
Antitussive (less common)

Horse (Equine)

Analgesia for visceral pain (colic)
Preanesthetic medication
Sedation in combination with alpha-2 agonists

Cattle (Bovine)

Analgesia for pain associated with surgery or trauma
Preanesthetic medication
Sedation in combination with xylazine

Small Ruminants (Sheep / Goat)

Analgesia for pain (visceral and somatic)
Preanesthetic medication

Rabbit & Small Mammals

Analgesia for moderate pain (postoperative, visceral)
Sedation in combination with other agents

Avian & Poultry

Analgesia for pain (limited studies)
Preanesthetic medication (in some species)

Exotic & Other Species

Analgesia in small mammals (ferrets, rodents) and reptiles (limited data)

Pharmacology & Mechanism of Action

Drug Class: Opioid agonist-antagonist analgesic | Pharmacological Group: Synthetic opioid (morphinan derivative)

Mechanism of Action: Butorphanol is a synthetic opioid with agonist activity at the kappa (κ) opioid receptor and antagonist/partial agonist activity at the mu (μ) opioid receptor. Its analgesic effects are primarily mediated through κ-receptor activation in the spinal cord and brain, leading to inhibition of ascending pain pathways and modulation of neurotransmitter release. The μ-antagonist properties contribute to its ceiling effect on respiratory depression and lower abuse potential compared to pure μ-agonists like morphine.

Pharmacodynamics: Butorphanol produces dose-dependent analgesia, sedation, and antitussive effects. In veterinary species, it provides visceral analgesia more effectively than somatic pain relief. It also causes minimal cardiovascular depression, but may cause transient bradycardia or hypertension in some species. Its antitussive effect is mediated centrally. The ceiling effect on respiratory depression is a notable safety advantage.

⚡ Pharmacokinetics Summary

Absorption: Well absorbed after subcutaneous (SC) and intramuscular (IM) administration. Oral bioavailability is low due to extensive first-pass metabolism (approximately 5-17% in dogs). Onset of action is rapid: 5-15 minutes after IV, 15-30 minutes after IM/SC.

Distribution: Widely distributed in tissues. Crosses the blood-brain barrier. Volume of distribution is moderate to high. Protein binding is approximately 80% in dogs and 60-80% in other species.

Metabolism: Extensively metabolized in the liver via hydroxylation and conjugation (glucuronidation). Major metabolite is hydroxybutorphanol, which has some analgesic activity. In cats, metabolism may be slower due to deficient glucuronidation pathways.

Excretion: Excreted primarily in urine (as metabolites) and to a lesser extent in feces. Biliary excretion may occur. In dogs, approximately 50-70% of the dose is excreted in urine within 24 hours.

Half-Life: Dogs: 2-3 hours (IV); Cats: 2-6 hours (IV); Horses: 1-2 hours (IV); Cattle: 1-2 hours (IV).

Bioavailability: IM/SC: nearly 100%; Oral: 5-17% in dogs; Intranasal: 60-70% in dogs (not commonly used).

Protein Binding: Approximately 80% in dogs, 60-80% in other species.

Available Formulations & Strengths

Injectable Solution 10 mg/mL (as butorphanol tartrate) (IV, IM, SC)

Oral Tablet 1 mg, 5 mg, 10 mg (not commonly used in veterinary medicine) (PO)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to butorphanol or other opioids
Severe respiratory depression or compromised respiratory function
Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days
Use in animals with head trauma or increased intracranial pressure (may worsen)
Use in animals with severe hepatic or renal impairment (use with caution)
Use in animals with cardiac arrhythmias or unstable cardiovascular disease (use with caution)

Warnings & Clinical Precautions:

May cause sedation and ataxia; use caution when handling animals.
In horses, may cause transient ataxia and excitement at higher doses.
In cats, may cause mydriasis and behavioral changes.
Use with caution in animals with hypothyroidism, Addison's disease, or severe debilitation.
May cause respiratory depression, especially in neonates or geriatric animals.
In food animals, extra-label use is prohibited in the US; withdrawal times must be estimated.
Butorphanol has a ceiling effect on respiratory depression, but high doses can still cause significant respiratory depression.
In dogs, may cause bradycardia or hypotension; monitor cardiovascular status.
Use with caution in animals with seizure disorders (may lower seizure threshold).

Adverse Effects & Reactions

Common:

Sedation
Ataxia
Decreased gastrointestinal motility (constipation)
Decreased appetite
Mydriasis (cats)
Behavioral changes (excitement or dysphoria)

Serious / Severe:

Respiratory depression
Bradycardia or hypotension
Cardiac arrhythmias
Seizures (rare)
Anaphylactoid reactions (rare)

Rare:

Hypersensitivity reactions
Hepatic enzyme elevations
Renal impairment (with prolonged use)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other opioids (e.g., morphine, fentanyl)	Additive respiratory depression and sedation; may precipitate withdrawal in opioid-dependent animals.	High
Sedatives/tranquilizers (e.g., acepromazine, dexmedetomidine, benzodiazepines)	Enhanced sedation and respiratory depression.	Moderate
MAO inhibitors (e.g., selegiline)	Risk of serotonin syndrome or hypertensive crisis.	High
Muscle relaxants (e.g., methocarbamol)	Additive muscle weakness and sedation.	Mild
Anticholinergics (e.g., atropine)	May exacerbate tachycardia or ileus.	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Severe respiratory depression
Bradycardia
Hypotension
CNS depression (stupor, coma)
Seizures (rare)
Muscle rigidity

Emergency Treatment Protocol: Provide supportive care. Administer oxygen and ventilatory support if needed. Administer an opioid antagonist such as naloxone (0.01-0.04 mg/kg IV, IM, SC) to reverse respiratory depression. Monitor cardiovascular function and treat arrhythmias if present. In severe cases, consider intravenous fluids and pressor support. Butorphanol overdose may be less dangerous than pure μ-agonists due to ceiling effect, but still requires aggressive treatment.

Food Animal Withdrawal Times

Butorphanol is not approved for use in food animals in the US. Extra-label use is prohibited under AMDUCA. For other countries, consult local regulations. If used extra-label, a withdrawal time of at least 7 days for meat and 72 hours for milk is often recommended, but official withdrawal times are not established.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), excursions permitted between 15-30°C (59-86°F).

Handling & Special Conditions: Protect from freezing. Keep in tightly closed container. Store away from heat and direct sunlight.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and cats (injectable solution) for pain relief and as a preanesthetic. Also approved for use in horses for analgesia. Not approved for food animals.

Extra-Label (Off-Label) Use: In the US, butorphanol is a controlled substance (C-IV) and requires a prescription. Extra-label use in food animals is prohibited under AMDUCA. In non-food animals, extra-label use is permitted under veterinary discretion.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Butorphanol is a valuable analgesic for moderate visceral pain in dogs and cats, but its duration of action is short (2-3 hours in dogs, 2-4 hours in cats). It is often used as a preanesthetic to reduce anesthetic requirements and provide smooth recovery. In horses, it is commonly used for colic pain, but may cause ataxia. In cats, it can cause behavioral excitement at higher doses. Butorphanol is a good choice for short-term pain management, but for prolonged pain, other analgesics (e.g., NSAIDs, full μ-agonists) may be more appropriate. Always monitor respiratory and cardiovascular status, especially in compromised patients. In food animals, avoid use due to regulatory restrictions.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)