Buprenorphine Hydrochloride

Opioid Analgesic (Partial Mu Agonist) Opioid Analgesics Rx Controlled C-III (US), C-III (Canada), varies by country

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV, IM, SC 0.01-0.02 mg/kg (IV/IM/SC) q6-12h Duration: As needed for pain
Notes: For postoperative pain, administer 30 minutes before end of surgery. Higher doses may be needed for severe pain but avoid exceeding 0.03 mg/kg due to ceiling effect.
Cat IV, IM, SC, OTM (oral transmucosal) 0.01-0.02 mg/kg (IV/IM/SC); 0.02-0.03 mg/kg (OTM) q6-12h Duration: As needed for pain
Notes: OTM administration is well absorbed via buccal mucosa; do not give orally (swallowed) as bioavailability is low. For chronic pain, may use 0.02 mg/kg OTM q8-12h.
Horse IV, IM 0.005-0.01 mg/kg (IV); 0.01-0.02 mg/kg (IM) q6-8h Duration: As needed for pain
Notes: May cause excitation in some horses; use with caution. For colic, use only after diagnosis to avoid masking signs.
Cattle IV, IM 0.01-0.02 mg/kg q8-12h Duration: As needed for pain
Notes: Extra-label use; observe withdrawal times. Not approved for food animals in many countries.
Sheep/Goats IV, IM 0.01-0.02 mg/kg q8-12h Duration: As needed for pain
Notes: Extra-label use; monitor for respiratory depression.
Rabbit IV, IM, SC 0.01-0.05 mg/kg q6-8h Duration: As needed for pain
Notes: Start at lower end; may cause GI stasis in rabbits, so use with supportive care.
Bird (e.g., psittacines) IM 0.01-0.05 mg/kg q6-8h Duration: As needed for pain
Notes: Limited studies; use with caution.
Ferret IM, SC 0.01-0.03 mg/kg q6-8h Duration: As needed for pain
Notes: May cause sedation.

Clinical Indications & Species Uses

General Indications
  • Management of moderate to severe pain
  • Preemptive analgesia
  • Adjunct to general anesthesia
Dog (Canine)
  • Postoperative pain management
  • Moderate to severe acute pain
  • Chronic pain (adjunctive therapy)
  • Preanesthetic medication
Cat (Feline)
  • Postoperative pain management
  • Moderate to severe acute pain
  • Chronic pain (e.g., osteoarthritis)
  • Preanesthetic medication
Horse (Equine)
  • Postoperative pain management
  • Moderate to severe acute pain
  • Analgesia for colic (with caution)
Cattle (Bovine)
  • Postoperative pain management
  • Analgesia for acute pain (e.g., lameness, surgery)
Small Ruminants (Sheep / Goat)
  • Postoperative pain management
  • Analgesia for acute pain
Rabbit & Small Mammals
  • Postoperative pain management
  • Analgesia for acute pain
Avian & Poultry
  • Postoperative pain management
  • Analgesia for acute pain (limited studies)
Exotic & Other Species
  • Analgesia in small mammals (e.g., ferrets, rodents)
  • Analgesia in reptiles (limited evidence)

Pharmacology & Mechanism of Action

Drug Class: Opioid Analgesic (Partial Mu Agonist) | Pharmacological Group: Opioid Analgesics

Mechanism of Action: Buprenorphine is a partial agonist at mu-opioid receptors and an antagonist at kappa-opioid receptors. It binds with high affinity to mu receptors, producing analgesia, but with a ceiling effect on respiratory depression and sedation. It also has a slow dissociation from the receptor, leading to a prolonged duration of action. Its analgesic effect is mediated by activation of descending inhibitory pathways and modulation of neurotransmitter release in the central nervous system.

Pharmacodynamics: Buprenorphine produces dose-dependent analgesia, sedation, and euphoria in some species. It has a high affinity for mu receptors, which can displace other opioids and block their effects. The ceiling effect on respiratory depression makes it safer than full agonists in overdose. It also causes minimal histamine release compared to morphine. In veterinary species, the duration of analgesia varies: in dogs, it lasts 6-12 hours; in cats, 6-12 hours; in horses, 4-6 hours; in rabbits, 6-8 hours.

⚡ Pharmacokinetics Summary

Absorption: Buprenorphine is well absorbed after parenteral administration. Oral bioavailability is low due to first-pass metabolism, but transmucosal (buccal) administration in cats provides effective absorption. After subcutaneous or intramuscular injection, peak plasma concentrations occur within 30 minutes to 1 hour.
Distribution: Buprenorphine is highly lipophilic, leading to extensive tissue distribution. It crosses the blood-brain barrier and placenta. Volume of distribution is large (e.g., ~3-8 L/kg in dogs). Protein binding is high (approximately 96%).
Metabolism: Buprenorphine is primarily metabolized in the liver by N-dealkylation to norbuprenorphine (via CYP3A4) and glucuronidation. Norbuprenorphine is an active metabolite with weaker analgesic activity. In dogs and cats, metabolism is hepatic; in horses, it is also hepatic.
Excretion: Excretion is primarily via feces (biliary excretion) and to a lesser extent urine. Buprenorphine undergoes enterohepatic recirculation, which contributes to its prolonged duration. In dogs, approximately 70% is excreted in feces and 20% in urine.
Half-Life: Dogs: 3-5 hours (but analgesic duration longer due to receptor binding); Cats: 6-12 hours; Horses: 2-4 hours; Rabbits: 3-5 hours.
Bioavailability: Subcutaneous: ~100% in dogs and cats; Intramuscular: ~100%; Oral transmucosal (cats): ~25-50%; Oral (PO): <10% due to first-pass effect.
Protein Binding: Approximately 96% (primarily to alpha and beta globulins).

Available Formulations & Strengths

Injectable Solution 0.3 mg/mL (as hydrochloride) (IV, IM, SC)
Injectable Solution (veterinary specific) 0.3 mg/mL (e.g., Vetergesic) (IV, IM, SC)
Transmucosal Gel (compounded) Various (e.g., 0.5 mg/mL) (Oral transmucosal (buccal))
Tablet (sublingual, human) 2 mg, 8 mg (not commonly used in veterinary) (Sublingual)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to buprenorphine or other opioids
  • Severe respiratory insufficiency or respiratory depression
  • Concurrent use with full mu-opioid agonists (may precipitate withdrawal)
  • Use in animals with head trauma or increased intracranial pressure (unless ventilated)
  • Use in animals with impaired consciousness or coma
  • Use in animals with known biliary tract disease (may cause spasm of Oddi)
  • Do not use in animals with known intolerance to opioids
Warnings & Clinical Precautions:
  • Use with caution in animals with hepatic or renal impairment
  • Use with caution in animals with hypothyroidism, adrenocortical insufficiency, or shock
  • May cause respiratory depression, especially at high doses or with other CNS depressants
  • May cause sedation, which can be pronounced in some species
  • In horses, may cause excitation or CNS stimulation; use with caution
  • In ruminants, may cause rumen stasis; monitor gastrointestinal function
  • In rabbits and rodents, may cause GI stasis; use with supportive care
  • May cause urine retention; monitor urinary output
  • Use with caution in very young, geriatric, or debilitated animals
  • May cause bradycardia; monitor heart rate
  • In cats, oral transmucosal administration should be placed on the buccal mucosa, not swallowed
  • Avoid extra-label use in food animals without proper withdrawal times

Adverse Effects & Reactions

Common:

  • Sedation
  • Euphoria or dysphoria (especially in cats and horses)
  • Miosis or mydriasis (species-dependent)
  • Bradycardia
  • Hypothermia
  • Decreased gastrointestinal motility
  • Vomiting (especially in dogs and cats)
  • Respiratory depression (dose-dependent)

Serious / Severe:

  • Severe respiratory depression
  • Cardiovascular collapse (rare)
  • Seizures (rare, especially in horses)
  • Anaphylactoid reactions (rare)
  • Ileus or GI stasis (especially in rabbits and ruminants)

Rare:

  • Hypotension
  • Urinary retention
  • Pruritus
  • Muscle rigidity
  • Paradoxical excitement

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Other opioids (full agonists) May precipitate withdrawal or reduce analgesic effect due to receptor competition High
Benzodiazepines Additive CNS depression and respiratory depression High
Barbiturates Additive CNS depression and respiratory depression High
Phenothiazines (e.g., acepromazine) Additive hypotension and sedation Moderate
Alpha-2 agonists (e.g., xylazine, dexmedetomidine) Additive sedation, bradycardia, and respiratory depression High
MAO inhibitors (e.g., selegiline) Risk of serotonin syndrome or hypertensive crisis High
Tricyclic antidepressants Potential for increased sedation and anticholinergic effects Moderate
CYP3A4 inhibitors (e.g., ketoconazole) May increase buprenorphine levels Moderate
CYP3A4 inducers (e.g., phenobarbital) May decrease buprenorphine levels Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Severe respiratory depression
  • Bradycardia
  • Hypotension
  • Miosis (or mydriasis in some species)
  • CNS depression (sedation, coma)
  • Muscle flaccidity
  • Hypothermia
  • Pulmonary edema (rare)

Emergency Treatment Protocol: Maintain airway and provide ventilatory support. Administer oxygen. Use a specific opioid antagonist such as naloxone (0.01-0.04 mg/kg IV, may need repeated doses due to buprenorphine's long duration). Alternatively, use doxapram (respiratory stimulant) if naloxone is unavailable. Monitor vital signs and provide supportive care (fluids, temperature regulation). In severe cases, consider continuous rate infusion of naloxone. Note that due to buprenorphine's high receptor affinity, higher doses of naloxone may be required.

Food Animal Withdrawal Times

Buprenorphine is not approved for use in food animals in the US. Extra-label use requires extended withdrawal periods; consult FARAD (Food Animal Residue Avoidance Databank) for specific recommendations. In some countries, withdrawal times may be established; for example, in cattle, meat withdrawal may be 7 days and milk 72 hours, but these are not official in the US.

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).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light. Keep in a secure, locked cabinet as a controlled substance. Do not freeze.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and cats in the US (e.g., Simbadol for cats). Also available as generic injectable. Not approved for food animals.

Extra-Label (Off-Label) Use: In the US, buprenorphine is a Schedule III controlled substance. Extra-label use in food animals is permitted under AMDUCA only with a valid veterinarian-client-patient relationship and requires extended withdrawal times. In the EU, buprenorphine is available as a veterinary product (e.g., Vetergesic) and is prescription-only. In some countries, it may be a controlled substance.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Buprenorphine is a valuable analgesic for moderate to severe pain in companion animals. Its partial mu agonist profile provides effective analgesia with a ceiling effect on respiratory depression, making it safer than full agonists. In cats, oral transmucosal administration is convenient and effective. In dogs, it is often used for postoperative pain. In horses, it can cause excitation, so it should be used with caution. For rabbits and rodents, monitor for GI stasis. Always use as part of a multimodal analgesic plan when appropriate. Due to its long duration of action, dosing intervals can be extended. As a controlled substance, proper record-keeping is required. In food animals, avoid use unless absolutely necessary and follow withdrawal guidelines.

References & Literature

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