Ketamine
Ketamine is a dissociative anesthetic used for induction, restraint and short procedures in many veterinary species. The racemic product contains R- and S-enantiomers. At lower exposures, ketamine is used as an adjunct analgesic, particularly when central sensitization contributes to pain. It is commonly incorporated into balanced injectable or inhalational anesthesia protocols.
Group
Dissociative anaesthetic and analgesic adjunct
Mechanism of Action
Ketamine acts mainly as a noncompetitive antagonist at NMDA receptors, limiting excitatory glutamate-mediated signaling. Disruption of communication between cortical and subcortical pathways contributes to dissociative anesthesia. NMDA blockade also reduces activity-dependent amplification of nociceptive signaling and central sensitization, supporting analgesia at subanesthetic exposures. Additional receptor and ion-channel interactions contribute to its overall anesthetic profile.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | IV | Combined IV/IM reported range 5.5-22 mg/kg, with lower doses intended for IV and higher for IM; exact route-specific endpoints are not assigned. Use adjunct sedation. | |
| General anaesthesia | Reference only | IM | Combined IV/IM reported range 5.5-22 mg/kg; higher doses are intended for IM but a separate IM range is not provided. | |
| Perioperative analgesia — Loading | 0.3–0.5 mg/kg | IV | ||
| Perioperative analgesia — Maintenance | 0.3–0.6 mg/kg/hour | IV | Continuous | May be increased to 1 mg/kg/hour if needed. In cats with other analgesics, 2-5 mcg/kg/min is a lower-rate alternative. |
| Postoperative analgesia | 0.12 mg/kg/hour | IV | Continuous | Up to 0.75 days; Continue at this reduced rate for up to 18 hours. |
| Light sedation | 1–2 mg/kg/hour | IV | Continuous | May be combined with other sedatives. |
| Opioid-associated pain adjunct | 0.1–1 mg/kg | PO, IM, SC | Every 4–6 h | With an opioid; mild-to-moderate pain protocol, not anaesthetic dosing. |
| Alternative intraoperative analgesia — Loading | 0.5 mg/kg | IV | ||
| Alternative intraoperative analgesia — Maintenance | 10–20 mcg/kg/min | IV | Continuous | |
| Alternative postoperative analgesia | 2–10 mcg/kg/min | IV | Continuous | Titrate within a balanced analgesic plan. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | IV | Combined IV/IM reported range 2-25 mg/kg; lower doses are intended IV. A sedative or benzodiazepine adjunct is recommended. | |
| General anaesthesia | Reference only | IM | Combined IV/IM reported range 2-25 mg/kg; higher doses are intended IM but exact route-specific bounds are not given. | |
| Perioperative analgesia — Loading | 0.3–0.5 mg/kg | IV | ||
| Perioperative analgesia — Maintenance | 0.3–0.6 mg/kg/hour | IV | Continuous | May be increased to 1 mg/kg/hour if needed. In cats with other analgesics, 2-5 mcg/kg/min is a lower-rate alternative. |
| Oromucosal restraint | 10 mg/kg | OTM | Once | Sprayed into the mouth; effect described as similar to IM administration. |
| Short-procedure combination | Reference only | IM | Ketamine 3-5 mg/kg plus dexmedetomidine 25 mcg/kg IM; an opioid may be included. This is a combination protocol, not ketamine-alone dosing. | |
| Ketamine-propofol anaesthesia | Reference only | IV | Induction uses ketamine 2 mg/kg plus propofol 2 mg/kg, mixed 1:1 as specified, followed by a combined-drug infusion of 10 mg/kg/hour. The total combination rate must not be treated as ketamine alone. | |
| IM restraint | 11 mg/kg | IM | Once | Racemic ketamine; provide suitable monitoring and adjuncts as indicated. |
| Minor procedures without muscle relaxation | 22–33 mg/kg | IM | Once | Not suitable as the sole technique when skeletal muscle relaxation is needed. |
| Opioid-associated pain adjunct | 0.1–1 mg/kg | IM, SC | Every 4–6 h | With an opioid. |
| Alternative intraoperative analgesia — Loading | 0.5 mg/kg | IV | ||
| Alternative intraoperative analgesia — Maintenance | 10–20 mcg/kg/min | IV | Continuous | |
| Alternative postoperative analgesia | 2–10 mcg/kg/min | IV | Continuous | Titrate within a balanced analgesic plan. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction | 2 mg/kg | IV | Once | Use appropriate premedication; horses must be sedated first. |
| Anaesthetic induction | 10 mg/kg | IM | Once | Usually combined with another sedative. |
| Analgesic infusion — Loading | 0.6 mg/kg | IV | ||
| Analgesic infusion — Maintenance | 0.4–0.8 mg/kg/hour | IV | Continuous | May increase to 1.2 mg/kg/hour if needed. |
| Intravenous anaesthetic maintenance | 2–6 mg/kg/hour | IV | Continuous | Part of a balanced anaesthetic plan with appropriate adjuncts. |
| Refractory neonatal seizures | 0.02 mg/kg/min | IV | Continuous | Foals only. |
| Field anaesthetic induction | 2.2–2.75 mg/kg | IV | Once | Only after full xylazine sedation; repeat 1/3-1/2 of the original xylazine/ketamine doses if required. Do not inject into an excited unsedated horse. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction | 2 mg/kg | IV | Once | Use appropriate premedication; horses must be sedated first. |
| Anaesthetic induction | 10 mg/kg | IM | Once | Usually combined with another sedative. |
| Anaesthetic induction | 2.2 mg/kg | IV | Once | After adequate sedation. |
| Analgesic infusion | 0.4–1.2 mg/kg/hour | IV | Continuous |
Sheep
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction | 2 mg/kg | IV | Once | Use appropriate premedication; horses must be sedated first. |
| Anaesthetic induction | 10 mg/kg | IM | Once | Usually combined with another sedative. |
| Premedicated anaesthesia | 22 mg/kg | IM | After atropine and acepromazine; IV 2-4 mg/kg may extend anaesthesia. | |
| Anaesthetic extension | 2–4 mg/kg | IV | As needed |
Pigs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction | 2 mg/kg | IV | Once | Use appropriate premedication; horses must be sedated first. |
| Anaesthetic induction | 10 mg/kg | IM | Once | Usually combined with another sedative. |
| Anaesthetic induction | 11 mg/kg | IM | Once | Atropine premedication is described. |
| Anaesthetic extension | 2–4 mg/kg | IV | As needed | |
| Post-sedation anaesthesia | 4.4 mg/kg | IM, IV |
Mice
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 50–100 mg/kg | IM, IP | ||
| Chemical restraint | 50 mg/kg | IV |
Rats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 50–100 mg/kg | IM, IP | ||
| Chemical restraint | 40–50 mg/kg | IV |
Hamsters
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 100 mg/kg | IM |
Gerbils
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 100 mg/kg | IM |
Guinea pigs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 10–30 mg/kg | IM |
Rabbits
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint | 20–50 mg/kg | IM | ||
| Chemical restraint | 15–20 mg/kg | IV |
Goats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Premedicated anaesthesia | 11 mg/kg | IM | After atropine then xylazine; maintain adequate timing and airway support. | |
| Anaesthetic extension | 2–4 mg/kg | IV | As needed | A separate 6 mg/kg extension is described for longer duration. |
Birds
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemical restraint below 100 g | 100–200 mg/kg | IM | Birds under 100 g; converted exactly from 0.1-0.2 mg/g. Do not apply to larger birds. | |
| Chemical restraint 250-500 g | 50–100 mg/kg | IM | Birds 250-500 g; 0.05-0.1 mg/g in the original regimen. | |
| Chemical restraint 500 g to 3 kg | 20–100 mg/kg | IM | Birds 500 g-3 kg; 0.02-0.1 mg/g. | |
| Chemical restraint over 3 kg | 20–50 mg/kg | IM | Birds over 3 kg; 0.02-0.05 mg/g. |
Indications
- Induction of general anesthesia in dogs, cats, horses and other veterinary species within an appropriate anesthetic protocol.
- Chemical restraint and anesthesia for selected short diagnostic or surgical procedures.
- Maintenance of total intravenous anesthesia in combination with other anesthetic and muscle-relaxant agents.
- Adjunctive perioperative or trauma-associated analgesia, particularly when hyperalgesia or central sensitization is a concern.
- Specialist treatment of refractory status epilepticus or selected refractory neonatal seizures as part of an emergency anticonvulsant protocol.
Contraindications
- Use cautiously with raised intracranial or intraocular pressure.
- Avoid as the sole anaesthetic in horses.
- Restrictive or hypertrophic cardiomyopathy requires particular caution.
Interactions
- Sedatives and other anaesthetics reduce ketamine requirements.
- Alkaline admixtures may precipitate ketamine hydrochloride.
Adverse effects
- Muscle rigidity, involuntary movement and emergence reactions
- Tachycardia, hypertension, salivation, hyperthermia and apnoea
- Prolonged infusions may slow equine intestinal transit.
Toxicity
Provide oxygen and ventilation as needed; control excessive stimulation and reassess cardiovascular function.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Ketamine 100 mg/mL injection Racemic ketamine activity, supplied as hydrochloride; not esketamine. | Injection | 100 mg / mL | IV, IM |
| Ketamine 10 mg/mL injection | Injection | 10 mg / mL | IV, IM |
| Ketamine 50 mg/mL injection | Injection | 50 mg / mL | IV, IM |
Monitoring and Administration
Pretreat horses with a suitable sedative and use a tranquilizer or benzodiazepine adjunct in small animals where indicated.
Lubricate exposed corneas because eyelids may remain open; monitor airway, respiration and cardiovascular status.
Mix compatible drugs immediately before administration rather than assuming long admixture stability.
Equine ketamine-xylazine alternative: ketamine 1.1 mg/kg plus xylazine 0.5 mg/kg IV. Standing-restraint combinations may use ketamine 0.05-0.1 mg/kg IV with xylazine and butorphanol.
Equine triple drip: 500 mg xylazine plus 2000 mg ketamine in 1 L of 5% guaifenesin in dextrose; reported guidance delivery is 1.1 mL/kg for induction then 2.4 mL/kg/hour for maintenance.
Morphine-lidocaine-ketamine analgesia targets morphine 0.24 mg/kg/hour, lidocaine 3 mg/kg/hour and ketamine 0.6 mg/kg/hour. The mixture uses ketamine 160 mg, lidocaine 600 mg and morphine 24 mg per nominal 500 mL fluid bag; these quantities do not yield the three stated target rates at one common fluid rate. Do not use this as an automatic mixing recipe.
The equine fixed example adds ketamine 3 g to a nominal 1 L fluid bag and delivers 125 mL/hour for 8 hours in an average horse. Patient weight and final volume must be specified before calculating a weight-based rate.
Small-mammal ketamine combinations vary markedly: mice ketamine 200 mg/kg plus diazepam 5 mg/kg IM/IP, or ketamine 100 plus xylazine 5-15 mg/kg IM/IP; rats ketamine 40-60 plus diazepam 5-10 mg/kg IP, or ketamine 40-75 plus xylazine 5-12 mg/kg IM/IP. Hamsters/gerbils: ketamine 50 plus diazepam 5 mg/kg IM; xylazine combinations are discouraged. Guinea pigs: ketamine 60-100 plus diazepam 5-8 mg/kg IM, or ketamine 85 plus xylazine 12-13 mg/kg IM.
Rabbit balanced techniques include diazepam 5-10 mg/kg IM followed 30 minutes later by ketamine 20-40 mg/kg IM for induction or 60-80 mg/kg IM without inhalants; IV induction uses diazepam 0.2-0.5 plus ketamine 10-15 mg/kg to effect. Xylazine combinations are discouraged in pet rabbits. Another rabbit combination is midazolam 0.05, buprenorphine 0.03 and ketamine 10 mg/kg IM; rodents use midazolam 5, ketamine 100 and buprenorphine 0.05 mg/kg IP.
Ferret injectable anaesthesia: butorphanol 0.1 mg/kg, ketamine 5 mg/kg and medetomidine 80 mcg/kg IM; supplementary isoflurane may be needed. Additional feline immobilization combines ketamine 1-5 mg/kg with butorphanol 0.2, medetomidine 0.015-0.02 and midazolam 0.05-0.2 mg/kg IM; painful procedures require suitable opioid analgesia.
Equine field alternatives use xylazine 1 mg/kg IV or 2 mg/kg IM before ketamine 2 mg/kg IV; adjuncts may include butorphanol 0.02-0.04 mg/kg IV, diazepam 0.03 mg/kg IV or guaifenesin to effect. Foal/pony infusion mixture: ketamine 500 mg plus xylazine 250 mg in 500 mL of 5% guaifenesin, 1.1 mL/kg for induction then 2-3 mL/kg/hour, with the lower rate in foals. Sheep maintenance example uses ketamine 2 mg/mL at a fixed 4 mL/minute and is not a universal weight-based rate.
Llama/alpaca combinations: ketamine 0.2-0.3 plus xylazine 0.2-0.3 and butorphanol 0.07-0.1 mg/kg IV, or ketamine/xylazine each 0.2-0.5 plus butorphanol 0.05-0.1 mg/kg IM. Recumbent procedural protocols use alpaca ketamine 4.6, xylazine 0.46, butorphanol 0.046 mg/kg IM; llama ketamine 3.7, xylazine 0.37, butorphanol 0.037 mg/kg IM. Half the ketamine/xylazine amounts may extend the procedure. Do not generalize fixed-volume cocktail examples to different concentrations.
Reptile balanced regimens pair medetomidine with ketamine IV or IM: small/medium land tortoises and iguanas 100-150 mcg/kg medetomidine plus 5-10 mg/kg ketamine; freshwater turtles 150-300 mcg/kg plus 10-20 mg/kg; smaller Aldabra tortoises 40-80 mcg/kg plus 4-8 mg/kg. A 200 kg Aldabra example used 40 mcg/kg plus 4 mg/kg and is not a universal fixed amount. Allow 30-40 minutes for peak effect; reversal uses atipamezole 4-5 times the medetomidine amount.
Bird combinations include ketamine 10-30 mg/kg IM with xylazine 2-6 mg/kg IM, ketamine 10-50 mg/kg IM with diazepam 0.5-2 mg/kg IM/IV, or ketamine 25-50 mg/kg IM with acepromazine 0.5-1 mg/kg IM. IV versions require a distinct reduced protocol; avoid xylazine in debilitated birds.
A second MLK description adds morphine 10 mg, lidocaine 120 mg and ketamine 100 mg to nominal 500 mL LRS at 10 mL/kg/hour, corresponding nominally to 0.2, 2.4 and 2 mg/kg/hour. It differs from the earlier inconsistent recipe. Final volume, coagent doses and feline lidocaine sensitivity must be assessed before use. Reports conflict on ketamine/diazepam same-syringe compatibility; administer separately unless the exact preparations and immediate-use compatibility are established.
The feline dexmedetomidine-opioid-ketamine table uses equal volumes of each of three solutions: dexmedetomidine 0.5 mg/mL, ketamine 100 mg/mL, and one of butorphanol 10 mg/mL, hydromorphone 2 mg/mL, morphine 15 mg/mL or buprenorphine 0.3 mg/mL. For 2-3 kg cats the volume of EACH drug is 0.025 mL mild, 0.05 mL moderate or 0.1-0.15 mL profound; 3-4 kg: 0.05, 0.1 or 0.2-0.25 mL; 4-6 kg: 0.1, 0.2 or 0.3-0.35 mL; 6-7 kg: 0.2, 0.3 or 0.4-0.45 mL; 7-8 kg: 0.3, 0.4 or 0.5-0.55 mL. All IM, with opioid selection individualized. Overlapping printed weight boundaries require clinical selection; these are not whole-tablet weight bands. Atipamezole reversal refers to the dexmedetomidine volume only and requires its specified formulation.