Ketamine HCl 200 mg/mL, Injectable Solution, 10mL
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- Product Type:
- Controlled Substance:
- Schedule CIII
While the anesthesia of wild animals is often carried out under difficult conditions, procedures for the anesthesia of zoo animals—many being of the same species encountered in the wild—can usually be streamlined to reduce much of the stress encountered by their wild counterparts. In the zoo setting, cooperative animals can receive drugs in the same manner as domestic animals. Procedures can be simplified when the animal has been made accustomed to injections, or any other behavior that may assist the veterinary staff. When an animal is uncooperative, the use of a pole syringe, compressed gas projectors such as blowpipes or CO2rifles and pistols may be needed to administer drugs via remote dart.
Anesthetic protocols and drugs formulated for rapid induction and recovery can minimize stress and the risk of injury to the animals. Assessment and improvement of anesthesia are important parts of the zoo veterinarian’s duties, since physiological and environmental disturbances can influence the well-being of animals.
Ketamine in the Zoo Setting
Ketamine is a dissociative general anesthetic and an NMDA-receptor antagonist. It has been FDA-approved for use in humans, sub-human primates, and cats, although it has been used in many other species. The FDA-approved indications for cats include, “for restraint, or as the sole anesthetic agent for diagnostic, or minor, brief, surgical procedures that do not require skeletal muscle relaxation… and in subhuman primates for restraint.”1
Ketamine is used to induce general anesthesia in many species and as a constant rate infusion to provide analgesia and decrease the amount of inhalant used to maintain a surgical plane of anesthesia. It has been used intranasally in combination with midazolam in cats to induce sedation.2 Ketamine can inhibit NMDA receptors in the CNS and can decrease the wind-up pain effect. There is increasing interest in using it to prevent exaggerated pain associated with surgery or chronic pain states in animals.1
Ketamine: Pharmacology and Pharmacokinetics
Ketamine is a rapid-acting general anesthetic that has significant analgesic activity and a relative lack of cardiopulmonary depressant effects in healthy animals. It is thought to induce both anesthesia and amnesia by functionally disrupting the CNS through over-stimulating the CNS or inducing a cataleptic state. Ketamine binds the phencyclidine-binding site of the NMDA receptors, which prevents glutamate, an excitatory neurotransmitter, from stimulating these receptors. Ketamine also interacts with opioid and monoaminergic receptors, which contributes to the antinociceptive effects of this drug. It is also believed that ketamine acts as an antagonist at the muscarinic receptor site, due to its anticholinergic effects (eg, bronchodilation, delirium, and sympathomimetic action); however, these symptoms may also be caused by direct stimulation of the sympathetic system.3 The thalamoneocortical system is depressed while the limbic system is activated. In cats, ketamine causes a slight hypothermic effect as body temperatures decrease on average by 1.6°C after high anesthetic doses (approximately 20 mg/kg).In most species, ketamine is metabolized in the liver principally by demethylation and hydroxylation. These metabolites, along with unchanged ketamine, are eliminated in the urine.1
In species where ketamine is FDA-approved, the following adverse reactions are listed by the manufacturer: “respiratory depression…following high doses, emesis, vocalization, erratic and prolonged recovery, dyspnea, spastic jerking movements, convulsions, muscular tremors, hypertonicity, opisthotonos and cardiac arrest. In the cat, myoclonic jerking and/or tonic/clonic convulsions can be controlled by ultrashort-acting barbiturates or acepromazine. These latter drugs must be given intravenously, cautiously, and slowly, to effect (approximately 1/6 to 1/4 of the normal dose may be required).”
(Package Insert; Ketaset®—Fort Dodge)
When used alone, ketamine may induce seizures. Seizures have been reported to occur in up to 20% of cats that receive ketamine (alone) at therapeutic dosages. Diazepam is suggested if treatment is necessary. It has been reported to rarely cause a variety of other CNS effects (mild CNS effects to blindness and death).1
The following drug interactions have either been reported or are theoretical in humans or animals receiving ketamine and may be of significance in veterinary patients.
BUPROPION: Concurrent use may decrease the seizure threshold.
CHLORAMPHENICOL (parenteral): May prolong the anesthetic actions of ketamine. Chloramphenicol did not prolong anesthesia in dogs receiving xylazine/ketamine in one study.
CNS DEPRESSANTS: Narcotics, barbiturates, or benzodiazepines may prolong the recovery time after ketamine anesthesia.
HALOTHANE: When used with halothane, ketamine recovery rates may be prolonged and the cardiac stimulatory effects of ketamine may be inhibited; close monitoring of cardiac status is recommended when using ketamine with halothane.
IVERMECTIN: It has been recommended not to use ivermectin in reptiles within 10 days of ketamine.4
MEDETOMIDINE: In dogs, medetomidine potentially could reduce the metabolism of ketamine via inhibition of CYB2B11 (in vitro). Any clinical significance is not clear at this time. Dexmedetomidine (used in dogs) would be expected to reduce interaction risks considerably.5
NEUROMUSCULAR BLOCKERS (eg, succinylcholine, tubocurarine): May cause enhanced or prolonged respiratory depression.
THEOPHYLLINE: In humans, ketamine may lower the seizure threshold; veterinary significance is unknown.
THYROID HORMONES: When given concomitantly with ketamine, thyroid hormones have induced hypertension and tachycardia in humans; beta-blockers (eg, propranolol) may be of benefit in treating these effects.
(Plumb’s Veterinary Drugs)
When using medetomidine in zoo, exotic and wildlife medicine refer to specific references, including:
a) Zoo Animal and Wildlife Immobilization and Anesthesia, 2nd ed. West, G., Heard, D., Caulkett, N. (eds.). Blackwell Publishing, 2014.
b) Handbook of Wildlife Chemical Immobilization, 3rd Ed. Kreeger, T.J. and J.M. Arnemo. 2007.
c) Fowler’s Zoo and Wild Animal Medicine Current Therapy, Volume 7, Miller, R.E., Fowler, M.E., Saunders. 2011.
d) Exotic Animal Formulary, 5th Ed. Carpenter, J.W., Saunders. 2017.
(Plumb’s Veterinary Drugs)
Where to buy Ketamine HCL 200mg/ml
Ketamine HCL injectable anesthesia is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. Ketamine HCL 200mg/ml by NexGen is indicated for use as an anesthetic to facilitate clinical examinations, clinical procedures and minor surgical procedures in zoo animals.
FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.
1Plumb’s Veterinary Drugs.
2Marjani M, Akbarinejad V, Bagheri M. Comparison of intranasal and intramuscular ketamine-midazolam combination in cats. Vet Anaesth Analg. 2015;42(2):178-181.
3Peltoniemi MA, Hagelberg NM, Olkkola KT, Saari TI. Ketamine: A Review of Clinical Pharmacokinetics and Pharmacodynamics in Anesthesia and Pain Therapy. Clin Pharmacokinet. 2016;55(9):1059-1077.
4Bays T. Practice tips for exotic animals. Paper presented at: Proceedings: WVC2009.
5Baratta MT, Zaya MJ, White JA, Locuson CW. Canine CYP2B11 metabolizes and is inhibited by anesthetic agents often co-administered in dogs. J Vet Pharmacol Ther. 2010;33(1):50-55.