作用機制: Ketamine exerts its effects through multiple central nervous system pathways:
* **NMDA Receptor Antagonism**: Acts as a non-competitive antagonist at the **N-methyl-D-aspartate (NMDA) receptor** → binds to the PCP site inside the calcium channel pore → prevents glutamate-mediated calcium influx → blocks central sensitization and prevents the "wind-up" phenomenon associated with chronic or severe pain.
* **Neurotransmitter Modulation**: Inhibits **GABA** and blocks the reuptake of **serotonin**, **norepinephrine**, and **dopamine** in the CNS.
* **CNS Dissociation**: Depresses the thalamoneocortical system (responsible for sensory perception) while simultaneously activating the limbic system (involved in memory and emotion).
* **Sympathetic Stimulation**: Increases sympathetic tone by promoting norepinephrine release → leads to increased heart rate, cardiac output, and blood pressure. *Note: Ketamine has direct negative inotropic effects on the myocardium, which are usually masked by this sympathetic surge unless the patient is catecholamine-depleted.*
各物種劑量
Sheep
Anesthesia · 22 mg/kg IM. To extend anesthetic time, may give ketamine intermittently IV at 2-4 mg/kg. · IM, IV · Once · Premedicate with atropine (0.22 mg/kg) and acepromazine (0.55 mg/kg).
Anesthesia · 2 mg/kg IV for induction, then 4 mL/minute constant infusion of ketamine in a concentration of 2 mg/mL in D5W · IV · CRI
Goats
Anesthesia · 11 mg/kg IM. To extend anesthesia give ketamine 2-4 mg/kg IV (shorter extension) or 6 mg/kg (longer extension). · IM, IV · Once · Give atropine 0.4 mg/kg, followed by xylazine 0.22 mg/kg IM 20-25 minutes later. Approximately 10 minutes after xylazine give ketamine.
Camelids (llamas and alpacas) - Anesthetic · butorphanol 0.07-0.1 mg/kg; ketamine 0.2-0.3 mg/kg; xylazine 0.2-0.3 mg/kg IV or butorphanol 0.05-0.1 mg/kg; ketamine 0.2-0.5 mg/kg; xylazine 0.2-0.5 mg/kg IM · IV or IM · Once
Camelids - Procedural pain (e.g., castrations) when recumbency is desired · Alpacas: butorphanol 0.046 mg/kg; xylazine 0.46 mg/kg; ketamine 4.6 mg/kg. Llamas: butorphanol 0.037 mg/kg; xylazine 0.37 mg/kg; ketamine 3.7 mg/kg. · IM · Once · All drugs combined in one syringe. May administer 50% of original dose of ketamine and xylazine during anesthesia to prolong effect up to 15 minutes.
Cats
Restraint · 11 mg/kg · IM · Once · Most clinicians recommend giving atropine or glycopyrrolate before use to decrease hypersalivation.
Diagnostic or minor surgical procedures not requiring skeletal muscle relaxation · 22-33 mg/kg · IM · Once
給藥途徑
IVIMSCPOIPSublingual (spray)
禁忌症
Prior hypersensitivity reactions to ketamine
Animals intended for human consumption
Use as a sole agent for major surgery (due to poor muscle relaxation and visceral analgesia)
Increased cerebrospinal fluid (CSF) pressure or head trauma
Significant hypertension, heart failure, or arterial aneurysms
Hypertrophic cardiomyopathy (HCM) in cats
Increased intra-ocular pressure or open globe injuries (relative)
Procedures involving the pharynx, larynx, or trachea (relative)
Preexisting seizure disorders (use with extreme caution)
Animals whose eyes are at risk of perforation
Raised intraocular pressure (IOP)
Raised intracranial pressure (ICP)
不良反應
Hypertension
Hypersalivation
Respiratory depression (at high doses or rapid IV administration)
Hyperthermia (especially in cats)
Emesis
Vocalization
Erratic and prolonged recovery (emergence delirium)
Dyspnea
Spastic jerking movements and muscular tremors
Seizures (up to 20% of cats at therapeutic doses)
Hypertonicity and opisthotonos
Cardiac arrest
Pain after IM injection
Eyes remain open (risk of corneal drying/ulceration)
Cardiovascular depression and arrhythmias (in animals with high sympathetic tone, shock, or severe CV disease)
Tachycardia (following high IV doses)
藥物相互作用
Chloramphenicol (parenteral) · May prolong the anesthetic actions of ketamine
CNS Depressants (Narcotics, barbiturates, diazepam) · May prolong the recovery time after ketamine anesthesia
Halothane · Recovery rates may be prolonged and the cardiac stimulatory effects of ketamine may be inhibited; close monitoring of cardiac status is recommended
Ivermectin · Recommended not to use ivermectin in reptiles within 10 days of ketamine
Neuromuscular blockers (e.g., succinylcholine, tubocurarine) · May cause enhanced or prolonged respiratory depression
Thyroid hormones · May induce severe hypertension and tachycardia; beta-blockers may be of benefit in treating these effects
Alpha-2 adrenergic agonists (e.g., medetomidine, dexmedetomidine) · Synergistic anaesthesia and prevention of muscle hypertonicity. Reversal of the alpha-2 agonist must be delayed until 45 minutes after ketamine administration to prevent unopposed ketamine excitation. · major
Benzodiazepines · Synergistic anaesthesia and prevention of ketamine-induced skeletal muscle hypertonicity. · moderate
監測
Level of anesthesia and analgesia
Respiratory function
Cardiovascular status (heart rate, rhythm, blood pressure)
Eyes (monitor to prevent drying or injury)
Body temperature (monitor for hyperthermia or hypothermia)
Heart rate and rhythm
Blood pressure
Respiratory rate and depth
Depth of anaesthesia
Corneal lubrication status
Quality of recovery (monitor for dysphoria)
過量
Ketamine has a wide therapeutic index (approximately 5 times greater than pentobarbital).
* **Signs of Toxicity**: When given too rapidly or in excessive doses, significant respiratory depression may occur.
* **Treatment**: Treatment using mechanically assisted respiratory support is recommended over the use of analeptic agents. In cats, yohimbine combined with 4-aminopyridine has been suggested for use as a partial antagonist.
Immobilizing agent (requiring more sedation) · butorphanol 0.2 mg/kg; medetomidine 0.015-0.02 mg/kg; midazolam 0.05-0.2 mg/kg; ketamine 1-5 mg/kg · IM · Once · For painful procedures consider adding buprenorphine at 0.02-0.04 mg/kg or substituting butorphanol/buprenorphine with morphine 0.5 mg/kg or hydromorphone 0.1 mg/kg.
Highly aggressive cats · 1 mL of ketamine · PO (spray) · Once · Sprayed into the open mouth or directed into the cat's mouth using a feline urethral catheter through cage bars.
NMDA antagonist for adjunctive pain control (mild to moderate pain) · 0.1-1 mg/kg · IM or SC · q4-6h · Use in conjunction with opioids.
Intraoperative use (if anesthesia induced with drug other than ketamine) · loading dose of 0.5 mg/kg IV, then an infusion of 10-20 micro-grams/kg/minute. A CRI of 2-10 micrograms/kg/minute can be used post-op. · IV · CRI
In combination with opioids or lidocaine · 0.5 mg/kg IV loading bolus followed by 10 micrograms/kg/min CRI during surgery and 2 micrograms/kg/min for 24 hrs following surgery. · IV · CRI · 24 hrs post-op
MLK (morphine/lidocaine/ketamine) mixture · Infuse at a rate of 10 mL/kg/hr (will provide morphine at 0.2 mg/kg/hr, lidocaine 40 micrograms/kg/minute, and ketamine 2 mg/kg/hr). · IV · CRI · To a 500 mL bag of LRS add 10 mg morphine sulfate, 120 mg lidocaine, and 100 mg ketamine.
Ferrets
Injectable anesthesia · Butorphanol 0.1 mg/kg, Ketamine 5 mg/kg, medetomidine 80 micrograms/kg. · IM · Once · Combine in one syringe. May need to supplement with isoflurane (0.5-1.5%) for abdominal surgery.
Cattle
Anesthesia · 2 mg/kg · IV · Once · Premedicate with atropine and xylazine, then give ketamine bolus.
Anesthesia · 2.2 mg/kg · IV · Once · After sedation.
CRI for adjunctive analgesia · 0.4-1.2 mg/kg/hr · IV · CRI
Horses
Field anesthesia · 2 mg/kg · IV · Once · Sedate with xylazine (1 mg/kg IV; 2 mg/kg IM) given 5-10 minutes before induction. Horse must be adequately sedated before giving ketamine.
Induction · 2.2-2.75 mg/kg · IV · Once · Initially give xylazine 1.1 mg/kg IV and wait for full sedative effect (4-8 minutes); then give ketamine as a bolus. Higher dose may be necessary for ponies, young Arabians, Hackneys, Thoroughbreds.
Foals and ponies induction/maintenance · For induction, give 1.1 mL/kg IV rapidly. Anesthesia may be maintained by constant IV infusion of 2-3 mL/kg/hr. · IV · CRI · Add 500 mg ketamine and 250 mg xylazine to 500 mL of 5% guaifenesin solution.
Induction of surgical colic patients · 1.6-2.2 mg/kg · IV · Once · Use guaifenesin to effect first.
Intra-operatively to reduce movement with light general anesthesia · 200 mg bolus (in a 454 kg horse) · IV · Once
Birds
Anesthesia (<100 grams: canaries, finches, budgies) · 0.1-0.2 mg/gm · IM · Once
Anesthesia (250-500 grams: parrots, pigeons) · 0.05-0.1 mg/gm · IM · Once
Anesthesia (500 grams-3 kg: chickens, owls, hawks) · 0.02-0.1 mg/gm · IM · Once
Anesthesia (>3 kg: ducks, geese, swans) · 0.02-0.05 mg/gm · IM · Once
In combination with xylazine · Ketamine 10-30 mg/kg IM; Xylazine 2-6 mg/kg IM · IM · Once · Birds less than 250 grams require a higher dosage (per kg). Xylazine not recommended in debilitated birds.
In combination with diazepam · Ketamine 10-50 mg/kg IM; Diazepam 0.5-2 mg/kg IM or IV · IM or IV · Once · Doses can be halved for IV use.
In combination with acepromazine · Ketamine 25-50 mg/kg IM; Acepromazine 0.5-1 mg/kg IM · IM · Once
Swine
Anesthesia · 11 mg/kg IM. To prolong anesthesia and increase analgesia give additional ketamine 2-4 mg/kg IV. · IM, IV · Once · Give atropine first.
Anesthesia · Ketamine (22 mg/kg) combined with acepromazine (1.1 mg/kg) · IM · Once
Anesthesia · 4.4 mg/kg · IM or IV · Once · After sedation.
SmallMammals
Mice: Chemical restraint (Alone) · 50-100 mg/kg IM or IP, 50 mg/kg IV · IM, IP, IV · Once
Mice: Chemical restraint (with diazepam) · Ketamine 200 mg/kg with Diazepam 5 mg/kg · IM or IP · Once
Mice: Chemical restraint (with xylazine) · Ketamine 100 mg/kg with Xylazine 5-15 mg/kg · IM or IP · Once
Rats: Chemical restraint (Alone) · 50-100 mg/kg IM or IP, 40-50 mg/kg IV · IM, IP, IV · Once
Rats: Chemical restraint (with diazepam) · Ketamine 40-60 mg/kg with Diazepam 5-10 mg/kg · IP · Once
Rats: Chemical restraint (with xylazine) · Ketamine 40-75 mg/kg with Xylazine 5-12 mg/kg · IM or IP · Once
Hamsters/Gerbils: Chemical restraint (Alone) · 100 mg/kg · IM · Once
Hamsters/Gerbils: Chemical restraint (with diazepam) · Ketamine 50 mg/kg with Diazepam 5 mg/kg · IM · Once
Guinea pig: Chemical restraint (Alone) · 10-30 mg/kg · IM · Once
Guinea pig: Chemical restraint (with diazepam) · Ketamine 60-100 mg/kg with Diazepam 5-8 mg/kg · IM · Once
Guinea pig: Chemical restraint (with xylazine) · Ketamine 85 mg/kg with Xylazine 12-13 mg/kg · IM · Once
Rabbits: Chemical restraint (Alone) · 20-60 mg/kg · IM or IV · Once
Rabbits: Chemical restraint (with diazepam) · Ketamine 60-80 mg/kg with Diazepam 5-10 mg/kg · IM · Once
Rabbits: Chemical restraint (with xylazine) · Ketamine 10 mg/kg with Xylazine 3 mg/kg · IV · Once
Rabbits: Chemical restraint (Alone) · 20-50 mg/kg IM or 15-20 mg/kg IV · IM or IV · Once
Rabbits: Induction (with diazepam) · Diazepam 5-10 mg/kg IM give ketamine 30 minutes after diazepam at 20-40 mg/kg IM or Diazepam 0.2-0.5 mg/kg and Ketamine 10-15 mg/kg (to effect) IV · IM or IV · Once
Rabbits: Anesthesia without inhalants (with diazepam) · Diazepam 5-10 mg/kg IM plus ketamine 60-80 mg/kg IM 30 minutes later · IM · Once
Rodents: Injectable anesthesia · midazolam (5 mg/kg) + ketamine (100 mg/kg) + buprenorphine (0.05 mg/kg) · IP · Once
Rabbits: Injectable anesthesia · Midazolam (0.05 mg/kg) + buprenorphine (0.03 mg/kg) + ketamine (10 mg/kg) · IM · Once
Dogs
Adjunct to anesthesia (geriatric/renal/liver dysfunction as premed prior to propofol/mask) · dexmedetomidine at 62.5 micrograms/m2. Combine with equal volumes of one of the opioids noted above and ketamine. · IM or IV · Once · Opioid concentrations: Butorphanol 10 mg/mL, Hydromorphone 2 mg/mL, Morphine 15 mg/mL, or Buprenorphine 0.3 mg/mL. Ketamine 100 mg/mL.
Slightly heavier sedation for radiographic procedures · Dexmedetomidine at 125 micrograms/m2. Combine with equal volumes of one of the opioids noted above and ketamine. · IM or IV · Once · For ASA class II or III dogs.
Minor surgery, Penn hip or OFA-types of radiographic procedures requiring muscle relaxation · Dexmedetomidine at 250 micrograms/m2. Combine with equal volumes of one of the opioids noted above and ketamine. · IM or IV · Once
Surgical plane of anesthesia for OHE, castration, or abdominal surgery · Dexmedetomidine at 375 micrograms/m2. Combine with equal volumes of one of the opioids noted above and ketamine. · IM or IV · Once · Provides rapid immobilization; lateral recumbency in 5-8 minutes.
Immobilizing extremely fractious dogs and wolf-hybrid dogs · Dexmedetomidine at 500 micrograms/m2. Combine with equal volumes of one of the opioids noted above and ketamine. · IM · Once · Rarely required.
NMDA antagonist for adjunctive pain control (mild to moderate pain) · 0.1-1 mg/kg · PO, IM or SC · q4-6h · Use in conjunction with opioids.
Intraoperative use (if anesthesia induced with drug other than ketamine) · loading dose of 0.5 mg/kg IV, then an infusion of 10-20 micrograms/kg/minute. A CRI of 2-10 micrograms/kg/minute can be used post-op. · IV · CRI
In combination with opioids or lidocaine · 0.5 mg/kg IV loading bolus followed by 10 micrograms/kg/min CRI during surgery and 2 micrograms/kg/min for 24 hrs following surgery. · IV · CRI · 24 hrs post-op
Reptiles
Medium to small land Tortoises · Medetomidine 100-150 micrograms/kg with ketamine 5-10 mg/kg · IV or IM · Once · Reversal of all dosages with atipamezole is 4-5 times the medetomidine dose.
Freshwater Turtles · Medetomidine 150-300 micrograms/kg with ketamine 10-20 mg/kg · IV or IM · Once
Giant Land Tortoises (200 kg Aldabra tortoise) · Medetomidine 40 micrograms/kg with ketamine 4 mg/kg · IV or IM · Once
Smaller Aldabra tortoises · Medetomidine 40-80 micrograms/kg with ketamine 4-8 mg/kg · IV or IM · Once · Wait 30-40 minutes for peak effect.
Iguanas · Medetomidine 100-150 micrograms/kg with ketamine 5-10 mg/kg · IV or IM · Once
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Marked respiratory depression (in some animals)
Skeletal muscle hypertonicity and spontaneous movement (if used alone)
Spacey, abnormal behaviour or dysphoria during recovery (1-2 hours)
Drug accumulation and prolonged recovery (with prolonged infusion)