Buprenorphine

Buprenorphine is an opioid analgesic used in dogs, cats and selected other species for perioperative and other pain management. Its high receptor affinity and slow dissociation support an effect that can outlast plasma concentration changes. Clinical onset, duration and exposure depend strongly on route and formulation.

Conventional injection, concentrated feline products and sustained-release preparations have distinct delivery and exposure profiles. Oral transmucosal administration is another veterinary application, especially in cats. Its partial mu-agonist character and high receptor affinity contribute to its clinical analgesic profile.

Group

Partial mu-opioid agonist

Mechanism of Action

Buprenorphine binds with high affinity to mu-opioid receptors and partially activates them; it also has kappa-antagonist activity. Mu-receptor signaling reduces neurotransmitter release from nociceptive pathways and increases inhibitory effects in spinal and supraspinal pain circuits, decreasing perception and transmission of pain.

Slow receptor dissociation contributes to persistent activity, while access to central sites and route-dependent absorption influence onset. Because it is a partial agonist, maximal receptor response differs from that of a full mu agonist, but the practical analgesic response still varies by species, dose and painful stimulus.

High receptor affinity influences competition with other opioids and the response to antagonists. Concentrated or sustained-release formulations alter the rate and duration of drug delivery, while the underlying opioid receptor target remains unchanged.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.006–0.02 mg/kg	IV, IM, SC	Every 4–8 h	Conventional 0.3 mg/mL immediate-release formulation.
Higher-dose analgesia	0.03–0.04 mg/kg	IV, IM, SC		Immediate-release formulation; no repeat interval is assigned in this alternative.
Surgical pain with concentrated solution	20 mcg/kg	IM, SC		Concentrated 1.8 mg/mL formulation; not a sustained-release product. Do not calculate this using the conventional preparation listed below.
Analgesic infusion — Loading	20 mcg/kg	IV	Once
Analgesic infusion — Maintenance	5 mcg/kg/hour	IV	Continuous
Epidural analgesia	0.003–0.006 mg/kg	EPIDURAL
Sustained-release analgesia	Reference only	SC		Use only the described sustained-release polymer: 120–270 mcg/kg subcutaneously, providing approximately 72 hours of effect. This must not be calculated from immediate-release product strength.
Oral transmucosal analgesia	120 mcg/kg	OTM		Studied gingival dose; large volumes can be lost or swallowed.
Analgesia	0.005–0.02 mg/kg	IM, IV, SC	Every 6–12 h	Immediate-release buprenorphine; reassess analgesia rather than assuming the whole interval is effective.
Analgesic infusion	2–4 mcg/kg/hour	IV	Continuous
Alternative analgesia	0.005–0.03 mg/kg	IV, IM, SC, EPIDURAL		Conventional immediate-release preparation; repeat interval is not assigned.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Analgesic infusion — Loading	20 mcg/kg	IV	Once
Analgesic infusion — Maintenance	12 mcg/kg/hour	IV	Continuous
Sustained-release analgesia	Reference only	SC		Use only the described sustained-release polymer: 120–270 mcg/kg subcutaneously, providing approximately 72 hours of effect. This must not be calculated from immediate-release product strength.
Analgesia	0.01–0.02 mg/kg	IV		Typical duration 4–6 hours; reassess before additional doses.
Analgesia	0.02 mg/kg	IM		Typical duration 4–6 hours; reassess before additional doses.
Sedation	0.02–0.04 mg/kg	IV, IM		Often combined with another sedative; sedation may be inconsistent.
Once-daily concentrated analgesia	Reference only	SC		Simbadol 1.8 mg/mL only: 0.24 mg/kg subcutaneously every 24 hours for up to 3 days; may begin before surgery. Do not substitute conventional buprenorphine.
Oral transmucosal analgesia	0.02–0.04 mg/kg	OTM	Every 8 h	Apply to gingival or sublingual mucosa; do not swallow.
Epidural analgesia	12.5 mcg/kg	EPIDURAL		Dilute in saline to total injection volume 0.3 mL/kg.
Analgesia	0.01–0.03 mg/kg	IM, IV, SC	Every 6–8 h	Conventional formulation; low-dose SC effects can be unreliable.
Oral transmucosal analgesia	0.01–0.03 mg/kg	OTM	Every 8 h	Apply to oral mucosa; do not reinterpret as swallowed oral dosing.
Analgesic infusion	1–3 mcg/kg/hour	IV	Continuous

Horses

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.005–0.01 mg/kg	IM		Short analgesic duration; excitement can outlast analgesia.
Neuroleptanalgesia	Reference only	IV		Separate IV combinations: buprenorphine 0.004 mg/kg with acepromazine 0.02 mg/kg; or buprenorphine 0.006 mg/kg with xylazine 0.07 mg/kg. Do not combine both sedative alternatives.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.01 mg/kg	IM	Every 6 h

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.01–0.05 mg/kg	SC, IM	Every 8–12 h

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.01–0.05 mg/kg	SC, IM, IV	Every 6–12 h
Rectal analgesia	0.5 mg/kg	RECTAL	Every 12 h
Premedication in compromised patients	0.05–0.1 mg/kg	SC
Premedication with midazolam	Reference only	IM		Healthy rabbits undergoing uncomplicated elective procedures: buprenorphine 0.02–0.06 mg/kg with midazolam 0.25–0.5 mg/kg IM within 20 minutes of the procedure, with an appropriate local block. Modify for unstable patients.

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.05 mg/kg	SC, IV	Every 8–12 h

Mice

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.05–0.1 mg/kg	SC	Every 12 h

Rats

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.01–0.05 mg/kg	SC, IV	Every 8–12 h
Analgesia	0.1–0.25 mg/kg	PO	Every 8–12 h

Indications

Perioperative and postoperative analgesia in dogs and cats within an appropriate multimodal plan.
Selected nonsurgical painful conditions requiring opioid analgesia.
Oral transmucosal analgesia using species- and formulation-specific regimens, particularly in cats.
Combination premedication or neuroleptanalgesia in which buprenorphine provides the opioid analgesic component.
Selected equine and exotic-animal analgesia using species-specific regimens.
Extended postoperative analgesia using an appropriate concentrated or sustained-release preparation.

Contraindications

Concentrations and release formulations must not be substituted without revising the regimen.
Use in horses can cause prolonged excitatory behavior and reduced gut motility.
Use cautiously with head injury, raised intracranial pressure, marked cardiopulmonary compromise, severe hepatic disease, biliary disease, hypothyroidism or adrenal insufficiency.

Interactions

May antagonize full mu agonists such as morphine and fentanyl.
Other sedatives enhance sedation.
Reported physical incompatibility with diazepam and lorazepam; do not mix without preparation-specific compatibility evidence.

Adverse effects

Sedation
Respiratory depression
Bradycardia
Equine excitement, locomotor activity and reduced intestinal motility

Toxicity

Naloxone may require higher doses for reversal because buprenorphine binds receptors strongly. Support ventilation in serious respiratory depression.

Preparations

Preparation	Form	Strength	Route
Buprenorphine 0.3 mg/mL injection	Injection	0.3 mg / mL	IV, IM, SC, OTM, EPIDURAL

Monitoring and Administration

Monitor respiration and heart rate, and reassess pain because onset can be delayed.

Apply oral transmucosal doses to gingival or sublingual mucosa; swallowing gives poor absorption. Larger volumes increase loss from the mouth.

A 2 mg sublingual tablet may be reformulated to 0.3 mg/mL in water or simple syrup; the described preparation is stable for 21 days at room temperature.

A separately described 3 mg/mL buccal solution uses 30 mg hydrochloride, 500 mg dextrose, 20 mg sodium citrate and 25 mg citric acid monohydrate in a final 10 mL water, pH 3.5–4.2. Reported stability is 90 days in amber glass refrigerated or at room temperature; do not confuse oral mucosal delivery with transdermal delivery.

Transdermal patch effects in dogs have delayed onset; feline patch studies did not demonstrate reliable analgesia. Human buccal films lack veterinary evaluation.