Ketamine: A tale of two enantiomers
Luke A. Jelen, Allan H. Young, James Stone
Journal of Psychopharmacology November 6, 2020 DOI: 10.1177/0269881120959644 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Review Pilot study Peer reviewed |
|---|---|
| Interventions | ketamine (S)-ketamine (R)-ketamine |
| Topics | Depression Ketamine Esketamine |
| Keywords | Antidepressant Pharmacology Nmda receptor Dissociative Hippocampus |
| Citations | 244 |
| Key findings | Ketamine and its enantiomers, particularly (R)-ketamine, show rapid and sustained antidepressant effects in treatment-resistant depression, though (S)-ketamine has dissociative effects and abuse potential. |
Abstract
The discovery of the rapid antidepressant effects of the dissociative anaesthetic ketamine, an uncompetitive N-Methyl-D-Aspartate receptor antagonist, is arguably the most important breakthrough in depression research in the last 50 years. Ketamine remains an off-label treatment for treatment-resistant depression with factors that limit widespread use including its dissociative effects and abuse potential. Ketamine is a racemic mixture, composed of equal amounts of (S)-ketamine and (R)-ketamine. An (S)-ketamine nasal spray has been developed and approved for use in treatment-resistant depression in the United States and Europe; however, some concerns regarding efficacy and side effects remain. Although (R)-ketamine is a less potent N-Methyl-D-Aspartate receptor antagonist than (S)-ketamine, increasing preclinical evidence suggests (R)-ketamine may have more potent and longer lasting antidepressant effects than (S)-ketamine, alongside fewer side effects. Furthermore, a recent pilot trial of (R)-ketamine has demonstrated rapid-acting and sustained antidepressant effects in individuals with treatment-resistant depression. Research is ongoing to determine the specific cellular and molecular mechanisms underlying the antidepressant actions of ketamine and its component enantiomers in an effort to develop future rapid-acting antidepressants that lack undesirable effects. Here, we briefly review findings regarding the antidepressant effects of ketamine and its enantiomers before considering underlying mechanisms including N-Methyl-D-Aspartate receptor antagonism, γ-aminobutyric acid-ergic interneuron inhibition, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic receptor activation, brain-derived neurotrophic factor and tropomyosin kinase B signalling, mammalian target of rapamycin complex 1 and extracellular signal-regulated kinase signalling, inhibition of glycogen synthase kinase-3 and inhibition of lateral habenula bursting, alongside potential roles of the monoaminergic and opioid receptor systems.