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Systematic (IUPAC) name
Clinical data
Legal status
CAS Number 33643-49-1
ATC code None
PubChem CID: 644025
ChemSpider 559099
Chemical data
Formula C13H16ClNO
Molecular mass 237.725 g/mol

Arketamine, also (R)-ketamine or R(–)-ketamine, is the (R)-(–) enantiomer of ketamine.[1][2][3] Unlike racemic ketamine and esketamine, the S(+) enantiomer of ketamine, arketamine is less potent pharmacologically and has never been approved or marketed as an enantiopure drug for clinical use, though it is still active.[1]

Relative to esketamine, arketamine possesses 4–5 times lower affinity for the PCP site of the NMDA receptor.[2][3][4] In accordance, arketamine is significantly less potent than racemic ketamine and especially esketamine in terms of anesthetic, analgesic, and sedative-hypnotic effects.[2][4] Racemic ketamine has weak affinity for the sigma receptor, where it acts as an agonist, whereas esketamine binds negligibly to this receptor, and so the sigma receptor activity of racemic ketamine lies in arketamine.[5] It has been suggested that this action of arketamine may play a role in the hallucinogenic effects of racemic ketamine and that it may be responsible for the lowering of the seizure threshold seen with racemic ketamine.[2][5] Esketamine inhibits the dopamine transporter about 8-fold more potently than does arketamine, and so is about 8 times more potent as a dopamine reuptake inhibitor.[6] Arketamine and esketamine possess similar potency for interaction with the muscarinic acetylcholine receptors.[7]

Paradoxically, arketamine shows greater and longer-lasting rapid antidepressant effects in animal models of depression relative to esketamine.[8][9][10] It has been suggested that this difference may have due to with the possibility of different activity of arketamine and esketamine and their respective metabolites at the α7-nicotinic receptor, as norketamine and hydroxynorketamine are potent antagonists of this receptor and markers of potential rapid antidepressant effects (specifically, increased mammalian target of rapamycin function) correlate closely with their affinity for it.[11][12][13] The picture is unclear however, and other mechanisms have also been implicated.[10]

In rodent studies, esketamine produced hyperlocomotion, prepulse inhibition deficits, and rewarding effects, while arketamine did not, indicating that arketamine may have a lower propensity for producing psychotomimetic effects and a lower abuse potential in addition to superior antidepressant efficacy.[10]


  1. ^ a b C.R. Ganellin; David J. Triggle (21 November 1996). Dictionary of Pharmacological Agents. CRC Press. pp. 1188–. ISBN 978-0-412-46630-4. 
  2. ^ a b c d John D. Current, M.D. Pharmacology for Anesthetists. PediaPress. pp. 263–. GGKEY:6RRHEC392UN. 
  3. ^ a b David T. Yew (6 March 2015). Ketamine: Use and Abuse. Taylor & Francis. pp. 269–. ISBN 978-1-4665-8340-5. 
  4. ^ a b Paul G. Barash; Bruce F. Cullen; Robert K. Stoelting; Michael Cahalan; M. Christine Stock (28 March 2012). Clinical Anesthesia. Lippincott Williams & Wilkins. pp. 456–. ISBN 978-1-4511-4795-7. 
  5. ^ a b Joris C. Verster; Kathleen Brady; Marc Galanter; Patricia Conrod (6 July 2012). Drug Abuse and Addiction in Medical Illness: Causes, Consequences and Treatment. Springer Science & Business Media. pp. 205–. ISBN 978-1-4614-3375-0. 
  6. ^ Nishimura M, Sato K (1999). "Ketamine stereoselectively inhibits rat dopamine transporter". Neurosci. Lett. 274 (2): 131–4. doi:10.1016/s0304-3940(99)00688-6. PMID 10553955. 
  7. ^ J. Vuyk; Stefan Schraag (6 December 2012). Advances in Modelling and Clinical Application of Intravenous Anaesthesia. Springer Science & Business Media. pp. 270–. ISBN 978-1-4419-9192-8. 
  8. ^ Zhang JC, Li SX, Hashimoto K (2014). "R (-)-ketamine shows greater potency and longer lasting antidepressant effects than S (+)-ketamine". Pharmacol. Biochem. Behav. 116: 137–41. doi:10.1016/j.pbb.2013.11.033. PMID 24316345. 
  9. ^ Hashimoto, Kenji (2014). "The R-Stereoisomer of Ketamine as an Alternative for Ketamine for Treatment-resistant Major Depression". Clinical Psychopharmacology and Neuroscience 12 (1): 72–73. doi:10.9758/cpn.2014.12.1.72. ISSN 1738-1088. 
  10. ^ a b c Yang C, Shirayama Y, Zhang JC, Ren Q, Yao W, Ma M, Dong C, Hashimoto K (2015). "R-ketamine: a rapid-onset and sustained antidepressant without psychotomimetic side effects". Transl Psychiatry 5: e632. doi:10.1038/tp.2015.136. PMID 26327690. 
  11. ^ van Velzen, Monique; Dahan, Albert (2014). "Ketamine Metabolomics in the Treatment of Major Depression". Anesthesiology 121 (1): 4–5. doi:10.1097/ALN.0000000000000286. ISSN 0003-3022. 
  12. ^ Paul RK, Singh NS, Khadeer M, Moaddel R, Sanghvi M, Green CE, O'Loughlin K, Torjman MC, Bernier M, Wainer IW (2014). "(R,S)-Ketamine metabolites (R,S)-norketamine and (2S,6S)-hydroxynorketamine increase the mammalian target of rapamycin function". Anesthesiology 121 (1): 149–59. doi:10.1097/ALN.0000000000000285. PMID 24936922. 
  13. ^ Singh NS, Zarate CA, Moaddel R, Bernier M, Wainer IW (2014). "What is hydroxynorketamine and what can it bring to neurotherapeutics?". Expert Rev Neurother 14 (11): 1239–42. doi:10.1586/14737175.2014.971760. PMID 25331415.