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Ketamine

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Image:Ketamine-2D-skeletal.png
Ketamine

2-(2-chlorophenyl)-2-methylamino-cyclohexan-1-one
IUPAC name
CAS number
6740-88-1 		ATC code

N01AX03 .

PubChem
3821 		DrugBank
APRD00493
Chemical formula {{{chemical_formula}}}
Molecular weight 237.725 g/mol
Bioavailability
Metabolism
Elimination half-life 2.5-3 hours.
Excretion renal (>90%)
Pregnancy category B
Legal status
Routes of administration IV, IM, Insufflated, oral, topical

Ketamine is a general dissociative anesthetic for human and veterinary use. Its hydrochloride salt is sold as Ketanest, Ketaset, and Ketalar. Pharmacologically, ketamine is classified as an NMDA receptor antagonist,[1] and, like other drugs of this class such as tiletamine, memantine, and phencyclidine (PCP), induces a state referred to as "dissociative anaesthesia."[2] As with other pharmaceuticals of this type, ketamine is used extramedically as a recreational drug.

Ketamine has a wide range of effects in humans, including analgesia, anesthesia, hallucination, arterial hypertension, and bronchodilation.[3] It is primarily used for the induction and maintenance of general anesthesia, usually in combination with some sedative drug. Other uses include sedation in intensive care, analgesia (particularly in emergency medicine), and treatment of bronchospasm. It is also a popular anesthetic in veterinary medicine.

Ketamine is a chiral compound. Most pharmaceutical preparations of ketamine are racemic, however reportedly some brands have (mostly undocumented) differences in enantiomeric proportions. The more active enantiomer, S-Ketamine, is also available for medical use under the brand name Ketanest S.[citation needed]

Contents

[edit] History

Ketamine was first reported in 1962 as part of an effort to find a safer anaesthetic alternative to Phencyclidine (PCP), which was more likely to cause hallucinations and seizures. The drug was first given to American soldiers during the Vietnam War, but today in the developed world its use on humans has been dramatically reduced because of concern about its potential to cause emergence phenomena because of the drug's possible psychotomimetic effects. However, it is still used widely in veterinary medicine, or as a battlefield anaesthetic in developing nations.[4]

Ketamine's side effects eventually made it a popular psychedelic in 1965. The drug was used in psychiatric and other academic research through the 1970s, culminating in 1978 with the publishing of John Lilly's The Scientist, a book documenting the author's ketamine, LSD, and isolation tank experiments. The incidence of recreational ketamine use increased through the end of the century, especially in the context of raves and other parties. The increase in illicit use prompted ketamine's placement in Schedule III of the United States Controlled Substance Act in August 1999. [5] In the United Kingdom, it became outlawed and labelled a Class C drug on January 1, 2006.[6] In Canada ketamine is classified as a Schedule I narcotic.[7] In Hong Kong, as of year 2000, Ketamine is regulated under Schedule 1 of Hong Kong Chapter 134 Dangerous Drugs Ordinance. It can only be used legally by health professionals, for university research purposes, or with a physician's prescription. [8]

[edit] Medical use

10 ml bottles of Ketamine
10 ml bottles of Ketamine
Indicated for:
  • Pain relief, surgical anaesthesia

Recreational uses:

Contraindications:
Side effects:

Severe: Impairs all senses, especially:

  • Sight
  • Balance
  • Sense of time

Cardiovascular:

  • Partial depressant

Gastrointestinal:

Musculoskeletal:

  • Relaxant

Neurological:

Respiratory:

  • Partial depressant/stimulant

In medical settings, Ketamine is usually injected intramuscularly [9], but it is also effective when injected intravenously, insufflated, smoked, or taken orally. [10]

Since it suppresses breathing much less than most other available anaesthetics [11], ketamine is still used in human medicine as a first-choice anaesthetic for victims with unknown medical history (e.g. from traffic accidents), in podiatry and other minor surgery, and occasionally for the treatment of migraine. There is ongoing research in France, Russia, and the U.S. into the drug's usefulness in pain therapy, depression suppression, and for the treatment of alcoholism[12] and heroin addiction.[13] In veterinary medicine, ketamine is often used for its anaesthetic and analgesic effects on cats, dogs, rabbits, rats, and other small animals. Veterinarians often use ketamine with sedative drugs to produce balanced anaesthesia and analgesia, and as a constant rate infusion to help prevent pain wind-up. Ketamine is used to manage pain among horses and other large animals, though it has less effect on bovines.

Ketamine may be used in small doses (0.1–0.5 mg/kg/h) as a local anesthetic, particularly for the treatment of pain associated with movement and neuropathic pain.[14] It has the added benefit of counter-acting spinal sensitization or wind-up phenomena experienced with chronic pain. At these doses, the psychotropic side effects are less apparent and well managed with benzodiazepines. [15] Ketamine is a co-analgesic, and so is most effective when used alongside a low-dose opioid; while it does have analgesic effects by itself, the higher doses required can cause disorientating side effects.[15] The combination of ketamine with an opiate or opioid is however particularly useful for pain caused by cancer. [16]

The effect of Ketamine on the respiratory and circulatory systems is different from that of other anaesthetics. When used at anaesthetic doses, it will usually stimulate rather than depress the circulatory system.[17] It is sometimes possible to perform ketamine anaesthesia without protective measures to the airways. Ketamine is also a potent analgesic and can be used in sub-anaesthetic doses to relieve acute pain; however, its psychotropic properties must be taken into account. Patients have reported vivid hallucinations, "going into other worlds" or "seeing God" while anesthetized, and these unwanted psychological side-effects have reduced the use of ketamine in human medicine. They can, however, usually be avoided by concomitant application of a sedative such as a benzodiazepine.[citation needed]

[edit] Experimental Antidepressant Use

The National Institute of Health News reports that a study of 18 patients led by Dr Carlos Zarate Jr. of the National Institute of Mental Health found that ketamine significantly improved treatment-resistant major depression within hours of injection. [18] The improvement lasted up to one week after the single dose. [19] The patients in the study were previously treatment resistant, having tried an average of six other treatments that failed. The importance of these findings was articulated by NIMH director Dr Thomas Insel: "To my knowledge, this is the first report of any medication or other treatment that results in such a pronounced, rapid, prolonged response with a single dose. These were very treatment-resistant patients." The researchers apparently attribute the effect to ketamine being an NMDA receptor antagonist. The study appears in the Archives of General Psychiatry. [20] Those findings of Zarate et al corroborate earlier findings by Berman et al. [21]

[edit] Treatment of addiction

The Russian doctor Evgeny Krupitsky (Clinical Director of Research for the Saint Petersburg Regional Center for Research in Addiction and Psychopharmacology) has gained encouraging results by using ketamine as part of a treatment for alcohol addiction which combines psychedelic and aversive techniques [22]. This method involved psychotherapy, controlled ketamine use and group therapy, and resulted in 60 of the 86 alcoholic males selected for the study remaining fully abstinent. He has also treated heroin addicts and reached the conclusion that ketamine reduces the craving for heroin without any adverse reaction [23].

[edit] Neuropharmacology

Ketamine, like Phencyclidine, is primarily a non-competitive antagonist of the NMDA receptor,[1] which opens in response to binding of the neurotransmitter glutamate. This NMDA receptor mediates the analgesic (reduction of pain) effects of ketamine at low doses.[24] Evidence for this is reinforced by the fact that naloxone, an opioid antagonist, does not reverse the analgesia. Studies also seem to indicate that ketamine is 'use dependent' meaning it only initiates its blocking action once a glutamate binds to the NMDA receptor.[24]

At high, fully anesthetic level doses, ketamine has also been found to bind to opioid mu receptors and sigma receptors.[24] Thus, loss of consciousness that occurs at high doses may be partially due to binding at the opioid mu and sigma receptors.[24]

Ketamine is racemic, and its R and S stereoisomers have different binding affinities: (S)-Ketamine has about four times greater affinity for the PCP site of the NDMA receptor than does (R)-Ketamine (in guinea pig brain).[24] (S)-ketamine seems to induce drowsiness more strongly than the (R) enantiomer; it is probable that (R)-ketamine is the stronger sigma agonist and so this enantiomer is likely to be responsible for the lowering of the seizure threshold that can occur with ketamine.[24] Since (S)-ketamine has greater analgesic effects and less hallucinogenic side effects than (R)-ketamine, the pure (S) enantiomer is sometimes preferred to the racemic mix for use in medical procedures, especially when lower doses are used for minor surgical procedures where the patient remains conscious during the operation.[citation needed]

skeletal formula of (R)-ketamine
ball-and-stick model of (R)-ketamine
skeletal formula of (S)-ketamine
ball-and-stick model of (S)-ketamine

The effects seem to take place mainly in the hippocampal formation and in the prefrontal cortex. This evidence, along with the NMDA receptor's connection with the memory formation process, explains ketamine's profound effects on memory and thought. These effects inhibit the filtering function of the brain and may mirror the sensory overload associated with schizophrenia and near death experiences.[citation needed]

The local anesthetic effects are likely from the blocking action of ketamine on sodium channels.[25] Its in vitro blocking potency of sodium channels in the resting state is similar to that of lidocaine[26]

[edit] Recreational use

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[edit] Illicit sale

10 ml bottle of liquid Ketamine drying out into a powder
10 ml bottle of liquid Ketamine drying out into a powder
Ketamine sold illicitly comes from diverted legitimate supplies or theft, primarily from veterinary clinics. In the US near its border with Mexico, the drug is most commonly acquired in Mexico, where it can be bought over the counter in veterinary clinics, and smuggled across the border. In 2003, Operation TKO was a probe conducted by the U.S. Drug Enforcement Agency (DEA). As a result of operation TKO, U.S. and Mexican authorities shut down the Mexico City company, Laboratorios Tokkyo, which was the biggest producer of ketamine in Mexico. According to the DEA, over 80% of ketamine found in the U.S. is of Mexican origin.[27] The World health Orginisation (WHO) Expert Committee on Drug Dependence in its thirty third report (2003).[28] recomended research into its recreational use/abuse due to growing concerns about its rising popularity in Europe, Asia and North America.

[edit] Methods of use

Ketamine is sold in either powdered or liquid form. In powdered form, its appearance is similar to that of pharmaceutical grade cocaine and can be insufflated (snorted), injected, or placed in beverages. It is also possible to smoke the drug in a joint or pipe, usually mixed with marijuana and tobacco. The smoke has a distinctive bitter taste but the effects of the high hit much faster than when insufflated or ingested. Oral use usually requires more material, but results in a longer trip. The liquid can be heated to drive off the solvent (usually saline), leaving powder. In therapeutic and psychedelic use, the liquid is typically injected intramuscularly. Intravenous injection is uncommon (recreationally), though possible. It is essentially identical in effect to intramuscular injection, but leads to a much quicker onset — usually within 10 to 15 seconds of dosing. Additionally, intravenous injection tends to lead to a more sudden and marked respiratory depression, especially if the solution is injected at too high of a potency (too fast). These factors make intravenous self-injection dangerous.

Some drug users' first contact with ketamine is accidental, from a pill sold as something else (commonly ecstasy). Ketamine is also commonly combined with other drugs to enhance their effects. There have been claims that ketamine has been used as a date rape drug because of its powerful dissociative effects, but this has never been documented.

[edit] Psychological effects

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Unlike true psychedelics, ketamine is powerfully reinforcing to many users and compulsive use is frequently reported. Both ketamine pioneer John Lilly and pseudonymous author D.M. Turner reported prolonged periods of "ketamine dependency", and the latter drowned in a bathtub while on ketamine.

Ketamine produces effects similar to PCP and DXM. Like other dissociative anesthetics in low- to upper-middle dosages, its hallucinogenic effects are only seen against a background lacking sensory stimulation, such as darkness. Some users claim that a trip due to ketamine use is as good or better than that of PCP or LSD because its overt hallucinatory effects are short-acting, lasting an hour or less in most cases. Effects on the senses, judgment, and coordination, however, can last for 18 to 24 hours. Standing up and moving may be more dangerous than lying still in one place.

Like the other dissociative anaesthetics DXM and PCP, hallucinations caused by ketamine are fundamentally different from those caused by tryptamines and phenethylamines. At low doses hallucinations are only seen when one is in a dark room with one's eyes closed, while at medium to high doses the effects are far more intense and obvious. These effects include changes in the perception of distances and durations as well as a slowing of the visual system's ability to update what the user is seeing. There are reports of high-dosage users being able to see their surroundings in two sharp images, as if the brain is unable to merge the images each eye is sending. Speech often sounds unintelligible and auditory hallucinations may occur. At high doses sounds can be out of sync with the users visual field.

Ketamine puts users in a dissociated state, meaning that they are less connected to both a sense of self and the reality around them. If a large enough amount is taken, users may go into or through a "K-hole", a state of wildly dissociated experience in which other worlds or dimensions that are difficult to describe with language are said to be perceived, all the while being completely unaware of their individual identities or the outside world. Users may feel as though their perceptions are located so deep inside the mind that the real world seems distant (hence the use of a "hole" to describe the experience). Some users may not remember this part of the experience after regaining consciousness, in the same way that a person may forget a dream. The "re-integration" process is slow, and the user gradually becomes aware of surroundings. At first, users may not remember their own names, or even know that they are human, or what that means. Movement is extremely difficult, and a user may not be aware that he or she has a body at all.

[edit] Danger

Main article: Olney's lesions

Like other NMDA Receptor Antagonists, it is postulated that ketamine can cause a certain kind of brain damage called Olney's Lesions.[29][30] Studies conducted on rats have shown that high doses of the NMDA receptor antagonist MK-801 caused vacuoles to form in certain regions of test rats' brains that developed into irreversible lesions, and experts say that it is possible that similar brain damage can occur in humans.[31]


[edit] Ketamine in the media

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[edit] Common Street Slang

The Greater Dallas Council on Alcohol and Drug Abuse (GDCADA) lists the following common slang terms for ketamine:[32]

  • Blind Squid
  • Breakfast Cereal
  • Cat Valium
  • Date Rape Drug
  • Green
  • K
  • Keller
  • Keller’s Day
  • Ket
  • Ketaject
  • Ketalar
  • Kit Kat
  • New Ecstasy
  • Psychedelic Heroin
  • Purple
  • Special-K
  • Special LA Coke
  • Super Acid
  • Super-C
  • Super-K
  • Vitamin K
  • Vit K

[edit] References

  1. ↑ 1.0 1.1 Harrison N, Simmonds M (1985). Quantitative studies on some antagonists of N-methyl D-aspartate in slices of rat cerebral cortex. Br J Pharmacol 84 (2): 381-91.
  2. ↑ Bergman S (1999). Ketamine: review of its pharmacology and its use in pediatric anesthesia. Anesth Prog 46 (1): 10-20.
  3. ↑ http://ncadi.samhsa.gov/govpubs/prevalert/v3i28.aspx
  4. ↑ Bonanno F (2002). Ketamine in war/tropical surgery (a final tribute to the racemic mixture). Injury 33 (4): 323-7.
  5. ↑ Ketamine - Schedule III of The Controlled Substances Act (CSA). Anestesiología Mexicana en Internet. URL accessed on 2006-12-22.
  6. ↑ http://news.bbc.co.uk/2/hi/uk_news/4564606.stm
  7. ↑ http://laws.justice.gc.ca/en/C-38.8/229687.html#rid-229689
  8. ↑ http://www.info.gov.hk/gia/general/200011/22/1122170.htm
  9. ↑ Lankenau S, Sanders B, Bloom J, Hathazi D, Alarcon E, Tortu S, Clatts M (2007). First injection of ketamine among young injection drug users (IDUs) in three U.S. cities. Drug Alcohol Depend 87 (2-3): 183-93.
  10. ↑ Reboso Morales J, González Miranda F (1999). [Ketamine]. Rev Esp Anestesiol Reanim 46 (3): 111-22.
  11. ↑ Heshmati F, Zeinali M, Noroozinia H, Abbacivash R, Mahoori A (2003). Use of ketamine in severe status asthmaticus in intensive care unit. Iran J Allergy Asthma Immunol 2 (4): 175-80.
  12. ↑ Krystal J, Madonick S, Perry E, Gueorguieva R, Brush L, Wray Y, Belger A, D'Souza D (2006). Potentiation of low dose ketamine effects by naltrexone: potential implications for the pharmacotherapy of alcoholism. Neuropsychopharmacology 31 (8): 1793-800.
  13. ↑ Jovaisa T, Laurinenas G, Vosylius S, Sipylaite J, Badaras R, Ivaskevicius J (2006). Effects of ketamine on precipitated opiate withdrawal. Medicina (Kaunas) 42 (8): 625-34.
  14. ↑ Lynch M, Clark A, Sawynok J, Sullivan M (2005). Topical amitriptyline and ketamine in neuropathic pain syndromes: an open-label study. J Pain 6 (10): 644-9.
  15. ↑ 15.0 15.1 Elia N, Tramèr M (2005). Ketamine and postoperative pain--a quantitative systematic review of randomised trials. Pain 113 (1-2): 61-70.
  16. ↑ Saito O, Aoe T, Kozikowski A, Sarva J, Neale J, Yamamoto T (2006). Ketamine and N-acetylaspartylglutamate peptidase inhibitor exert analgesia in bone cancer pain. Can J Anaesth 53 (9): 891-8.
  17. ↑ Adams H (1997). [S-(+)-ketamine. Circulatory interactions during total intravenous anesthesia and analgesia-sedation]. Anaesthesist 46 (12): 1081-7.
  18. ↑ NIH. "Experimental Medication Kicks Depression in Hours Instead of Weeks" NIH News, August 7, 2006
  19. ↑ Khamsi, R. "Ketamine relieves depression within hours" New Scientist, 08 August 2006.
  20. ↑ Zarate C, Singh J, Carlson P, Brutsche N, Ameli R, Luckenbaugh D, Charney D, Manji H (2006). A randomized trial of an N-methyl-D-aspartate antagonist in treatment-resistant major depression. Arch Gen Psychiatry 63 (8): 856-64.
  21. ↑ Berman R, Cappiello A, Anand A, Oren D, Heninger G, Charney D, Krystal J (2000). Antidepressant effects of ketamine in depressed patients. Biol Psychiatry 47 (4): 351-4.
  22. ↑ http://www.eleusis.us/resource-center/references/acamethod.php
  23. ↑ http://www.eleusis.us/resource-center/references/ketamine-psychotherapy-heroin.pdf
  24. ↑ 24.0 24.1 24.2 24.3 24.4 24.5 http://sulcus.berkeley.edu/mcb/165_001/papers/manuscripts/_962.html
  25. ↑ Benoit E (1995). Effects of intravenous anaesthetics on nerve axons. Eur J Anaesthesiol 12 (1): 59-70.
  26. ↑ Wagner L, Gingrich K, Kulli J, Yang J (2001). Ketamine blockade of voltage-gated sodium channels: evidence for a shared receptor site with local anesthetics. Anesthesiology 95 (6): 1406-13.
  27. ↑ http://www.dea.gov/pubs/pressrel/pr121505.html
  28. ↑ http://whqlibdoc.who.int/trs/WHO_TRS_915.pdf
  29. ↑ Olney J, Labruyere J, Price M (1989). Pathological changes induced in cerebrocortical neurons by phencyclidine and related drugs. Science 244 (4910): 1360-2.
  30. ↑ Hargreaves R, Hill R, Iversen L. Neuroprotective NMDA antagonists: the controversy over their potential for adverse effects on cortical neuronal morphology. Acta Neurochir Suppl (Wien) 60: 15-9.
  31. ↑ http://www.erowid.org/chemicals/dxm/dxm_health2.shtml
  32. ↑ GDCADA facts and statistics on Ketamine. Retrieved on February 9, 2007.

[edit] See also

[edit] External links


v·d·e
Dissociative hallucinogens
2-MDP - Dexoxadrol - Dextromethorphan - Dizocilpine - Efavirenz - Esketamine - Etoxadrol - Ketamine - Muscimol - Nitrous oxide - PCE - PCP - PCPy - Salvinorin A - Pentazocine - TCP - Tifluadom - Tiletamine - Xenon


v·d·e
Anesthetic: General anesthetics (N01A)
Barbiturates Hexobarbital, Methohexital, Narcobarbital, Thiopental
Ethers Diethyl ether, Desflurane, Enflurane, Isoflurane, Methoxyflurane, Methoxypropane, Sevoflurane, Vinyl ether
Haloalkanes Chloroform, Halothane, Trichloroethylene
Opioids Alfentanil, Anileridine, Fentanyl, Phenoperidine, Remifentanil, Sufentanil
Others Alfaxalone, Droperidol, Etomidate, gamma-Hydroxybutyric acid, Ketamine/Esketamine, Minaxolone, Nitrous oxide, Propanidid, Propofol, Xenon

<!_- de:Ketamin es:Ketamina fr:Kétamine it:Ketamina he:קטמין nl:Ketamine ja:ケタミン pl:Ketamina pt:Ketamina fi:Ketamiini sv:Ketamin th:คีตามีน zh:氯胺酮 --->

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