Butorphanol

Butorphanol is a mixed-action opioid with analgesic, sedative and antitussive properties. It is used alone for selected purposes and commonly with other sedatives for restraint or anesthetic premedication. Analgesia is generally shorter and less robust than that provided by full mu-opioid agonists, especially for severe somatic or postoperative pain.

Its veterinary roles include equine visceral pain, combination sedation and suppression of selected nonproductive cough in dogs. The relative contributions of analgesia, sedation and cough suppression vary with species, exposure and the clinical setting.

Group

Kappa-opioid agonist and mu antagonist

Mechanism of Action

Butorphanol acts principally as a kappa-opioid receptor agonist with weak antagonist or low-efficacy activity at mu receptors. Kappa signaling modifies nociceptive processing and contributes to sedation, with useful visceral analgesia in some species. The receptor profile produces a different maximal effect from a full mu agonist.

Central suppression of the cough reflex underlies its antitussive use. This effect can occur independently of the degree of analgesia, explaining why usefulness for cough does not establish adequate control of a severe painful procedure.

Its relatively short analgesic action and mixed receptor behavior influence combination use. It can modify or partially oppose effects of a full mu agonist, while combination with sedatives can deepen restraint without proportionately improving all forms of pain control. Redosing based only on apparent wakefulness can therefore misjudge its clinical effect.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Cough suppression	0.055 mg/kg	SC	Every 6–12 h
Cough suppression	0.011 mg/kg	IM
Cough suppression	0.5–1 mg/kg	PO	Every 6–12 h
Sedation and premedication	0.2–0.4 mg/kg	IV, IM, SC		May be combined with acepromazine or another sedative.
Analgesia	0.2–0.4 mg/kg	IV, IM, SC	Every 2–4 h
Analgesia	1–4 mg/kg	PO	Every 6 h
Analgesic infusion — Loading	0.2–0.4 mg/kg	IV	Once
Analgesic infusion — Maintenance	0.1–0.2 mg/kg/hour	IV	Continuous
Cough suppression	0.055–0.11 mg/kg	SC	Every 6–12 h	Up to 7 days
Cough suppression	0.55–1.1 mg/kg	PO	Every 6–12 h	Up to 7 days
Cough suppression	0.05–1 mg/kg	PO	Every 6–12 h	Titrate to cough control without excessive sedation.
Cough suppression	0.55–1.1 mg/kg	PO	As needed
Alternative analgesia	0.1–0.5 mg/kg	IV, IM, SC		Sedation may outlast analgesia; effect on pain can last an hour or less.
Epidural analgesia	0.25 mg/kg	EPIDURAL		Use preservative-free diluent/local anesthetic in a procedure-specific epidural plan; reported onset under 30 minutes and duration 2–4 hours.
Partial reversal of full mu agonists	0.05–0.1 mg/kg	IV		May reduce sedation/respiratory depression while retaining some analgesia; monitor clinical response.
Immobilization combination	Reference only	IM		IM butorphanol 0.2 mg/kg plus medetomidine 0.001–0.01 mg/kg and midazolam 0.05–0.2 mg/kg. A higher medetomidine alternative uses 0.01–0.02 mg/kg; additional anesthetic or analgesic choices depend on the procedure.
Analgesic infusion	0.1–0.4 mg/kg/hour	IV	Continuous
Cisplatin-associated emesis prevention	0.4 mg/kg	IM	Once	Administer 30 minutes before cisplatin infusion.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.2–0.8 mg/kg	IV, SC	Every 2–6 h
Analgesia	1.5 mg/kg	PO	Every 4–8 h
Sedation	0.2–0.5 mg/kg	IV, IM		Use the lower 0.2 mg/kg dose when combined with other agents for short procedures.
Analgesic infusion — Loading	0.2–0.4 mg/kg	IV	Once
Analgesic infusion — Maintenance	0.1–0.2 mg/kg/hour	IV	Continuous
Alternative analgesia	0.1–0.5 mg/kg	IV, IM, SC		Sedation may outlast analgesia; effect on pain can last an hour or less.
Epidural analgesia	0.25 mg/kg	EPIDURAL		Use preservative-free diluent/local anesthetic in a procedure-specific epidural plan; reported onset under 30 minutes and duration 2–4 hours.
Partial reversal of full mu agonists	0.05–0.1 mg/kg	IV		May reduce sedation/respiratory depression while retaining some analgesia; monitor clinical response.
Immobilization combination	Reference only	IM		IM butorphanol 0.2 mg/kg plus medetomidine 0.001–0.015 mg/kg and midazolam 0.05–0.2 mg/kg. A higher-sedation alternative uses medetomidine 0.015–0.02 mg/kg; ketamine 1–5 mg/kg may be added if needed.
Postoperative infusion with ketamine	Reference only	IV		Butorphanol loading 0.1–0.2 mg/kg IV followed by 0.1–0.2 mg/kg/hour; ketamine loading 0.1 mg/kg IV followed by 0.4 mg/kg/hour is a separate concurrent component.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.2–0.4 mg/kg	IV	Every 3–4 h
Lower-dose analgesia	0.02–0.1 mg/kg	IV		Lower doses, including 0.1 mg/kg, may limit intestinal hypomotility.
Lower-dose analgesia	0.04–0.2 mg/kg	IM
Sedation	0.01–0.06 mg/kg	IV
Analgesic infusion	13–24 mcg/kg/hour	IV	Continuous
Analgesia	0.1 mg/kg	IV	Every 3–4 h	Up to 2 days
Abdominal pain	0.01–0.02 mg/kg	IV		May be used alone or with a separate xylazine regimen.
Foal analgesia	0.1–0.2 mg/kg	IV, IM		Foals only.
Postoperative analgesic infusion	Reference only	IV		A reported regimen loads 17.8 mcg/kg then infuses 23.7 mcg/kg/hour; the loading route is not independently specified. Another regimen infuses 13 mcg/kg/hour without an assigned loading dose.
Cough suppression	0.02 mg/kg	IM	Every 8–12 h
Field anesthesia adjunct	Reference only	IV		Give xylazine 1 mg/kg IV or 2 mg/kg IM and allow 5–10 minutes or longer for IM effect. Only after adequate sedation, ketamine 2 mg/kg IV may be used. Butorphanol 0.02–0.04 mg/kg IV can supplement inadequate sedation before ketamine; alternatives include diazepam 0.03 mg/kg IV or 5% guaifenesin to effect. Do not induce with ketamine in an inadequately sedated horse.

Ruminants

Use / stage	Dose	Route	Schedule	Instructions
Analgesia	0.05–0.2 mg/kg	IV

Cattle

Use / stage	Dose	Route	Instructions
Sedation with xylazine	0.01–0.02 mg/kg	IV	Only in the stated xylazine combination.
Analgesia	0.02–0.25 mg/kg	IV, SC
Adult surgical analgesia	20–30 mg/animal	IV	Adult cattle; optional pretreatment with 10 mg xylazine is described.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Sedation and analgesia	0.05–0.1 mg/kg	IM, SC
Analgesia	0.05–0.5 mg/kg	SC, IM	Every 4 h
Injectable anesthetic combinations	Reference only	IM		Alternatives include butorphanol 0.2 mg/kg with xylazine 2 mg/kg IM; or butorphanol 0.1 mg/kg, ketamine 5 mg/kg and medetomidine 80 mcg/kg IM; or butorphanol 0.2 mg/kg, tiletamine/zolazepam 1.5 mg/kg and xylazine 1.5 mg/kg IM. Do not merge the alternatives.
Postoperative analgesic infusion	Reference only	IV		Loading 0.1–0.2 mg/kg followed by 0.1–0.2 mg/kg/hour; the excerpt does not explicitly assign the loading route, so the full instruction is retained as a protocol.

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Postoperative analgesic infusion	Reference only	IV		Loading 0.1–0.2 mg/kg followed by 0.1–0.2 mg/kg/hour; the excerpt does not explicitly assign the loading route, so the full instruction is retained as a protocol.
Chemical restraint	0.1–0.5 mg/kg	IV
Postoperative analgesia	0.1–0.5 mg/kg	IV, SC	Every 2–4 h
Postoperative analgesia	0.4 mg/kg	SC	Every 4–6 h

Birds

Use / stage	Dose	Route	Schedule	Instructions
Analgesia and sedation	1–4 mg/kg	IM, IV	Every 2–3 h
Analgesia and sedation	1–4 mg/kg	IM, IV, PO	Every 4 h

Alpacas

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.1 mg/kg	IM
Sedation	10 mg/animal	IM
Analgesia	0.1 mg/kg	IV, IM, SC	Every 4–6 h
Injectable anesthesia	Reference only	IM		Alternative combinations: butorphanol 0.07–0.1 mg/kg, ketamine 0.2–0.3 mg/kg and xylazine 0.2–0.3 mg/kg IV; or butorphanol 0.05–0.1 mg/kg, ketamine 0.2–0.5 mg/kg and xylazine 0.2–0.5 mg/kg IM. These are component-specific protocols.
Procedural anesthesia	Reference only	IM		IM combination: butorphanol 0.046 mg/kg, xylazine 0.46 mg/kg and ketamine 4.6 mg/kg. If needed, half the original ketamine/xylazine doses can extend anesthesia; do not repeat the entire mixture automatically.

Llamas

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.1 mg/kg	IM
Sedation	10 mg/animal	IM
Analgesia	0.1 mg/kg	IV, IM, SC	Every 4–6 h
Injectable anesthesia	Reference only	IM		Alternative combinations: butorphanol 0.07–0.1 mg/kg, ketamine 0.2–0.3 mg/kg and xylazine 0.2–0.3 mg/kg IV; or butorphanol 0.05–0.1 mg/kg, ketamine 0.2–0.5 mg/kg and xylazine 0.2–0.5 mg/kg IM. These are component-specific protocols.
Procedural anesthesia	Reference only	IM		IM combination: butorphanol 0.037 mg/kg, xylazine 0.37 mg/kg and ketamine 3.7 mg/kg. Allow quiet induction and adequate onset time.

Reptiles

Use / stage	Dose	Route	Schedule	Instructions
Historical analgesia	0.05–1 mg/kg	IM, IV, PO, SC	Every 12 h	Broad historical reptile/amphibian recommendation; species-specific efficacy varies. Turtles and tortoises may show respiratory depression with limited analgesia.

Indications

Selected short-duration or mild-to-moderate painful conditions.
Equine abdominal or visceral pain, including intermittent or infusion-based analgesia.
Sedation, chemical restraint and anesthetic premedication, commonly in combination with other sedatives.
Suppression of selected troublesome nonproductive cough in dogs.
Analgesic supplementation within selected procedural or perioperative combinations.
Specialist partial reversal or modification of full mu-opioid agonist effects.

Contraindications

Use cautiously where reduced intestinal motility is undesirable, particularly in horses.
Avoid cough suppression with copious lower-airway secretions; assess hepatic disease and cardiopulmonary reserve.
ABCB1/MDR1-mutant dogs may have prolonged sedation; reduce initial doses according to genotype and clinical response.

Interactions

May oppose full mu agonists.
Other sedatives enhance depression.
Do not mix with sodium barbiturates.

Adverse effects

Sedation
Respiratory depression at high exposure
Dysphoria
Constipation and reduced intestinal motility
Equine excitement

Toxicity

Support breathing if depressed; naloxone can reverse serious opioid effects.

Preparations

Preparation	Form	Strength	Route
Butorphanol 1 mg tablet	Tablet	1 mg / tablet	PO
Butorphanol 5 mg tablet	Tablet	5 mg / tablet	PO
Butorphanol 10 mg tablet	Tablet	10 mg / tablet	PO
Butorphanol 0.5 mg/mL injection	Injection	0.5 mg / mL	IV, IM, SC
Butorphanol 1 mg/mL injection	Injection	1 mg / mL	IV, IM, SC
Butorphanol 2 mg/mL injection	Injection	2 mg / mL	IV, IM, SC
Butorphanol 10 mg/mL injection	Injection	10 mg / mL	IV, IM, SC

Monitoring and Administration

Monitor heart rate, breathing and pain frequently; analgesia is often only about an hour.

An approximate ceiling of 0.8 mg/kg is described for routine small-animal use. This is a weight-based ceiling, not a total-mg cap.

Birds may need substantially different doses because of rapid clearance; the cited 2–4 mg/kg every 2–4 hours lacks an administration route and is not generalized into a calculator regimen.

One pharmacogenetic recommendation reduces doses by 25% in heterozygous ABCB1/MDR1 dogs and by approximately 30–50% in homozygous mutants. Monitor sedation and respiration.

Doses are expressed as butorphanol base activity. A human salt-labelled preparation can require conversion: 1 mg tartrate salt corresponds to 0.68 mg base; do not apply this to products already labelled in base equivalents.