In a finding described as 'unambiguous' by researchers, ketamine has been shown at a molecular level to bind to and activate mu-opioid receptors—the same targets as traditional opioids. The study, published this week, challenges the long-held assumption that ketamine’s primary mechanism of action is through NMDA receptor antagonism, which was thought to produce its dissociative and antidepressant effects.
Dr. [Lead Researcher], a pharmacologist at [Institution] who led the study, explained that the team used advanced molecular imaging and binding assays to observe ketamine interacting with opioid receptors in ways that had previously been overlooked. “This provides clear molecular evidence that ketamine is an opioid,” they said, though they cautioned that the practical implications for its clinical use are still under investigation.
Ketamine has gained popularity in recent years as a rapid-acting treatment for treatment-resistant depression, often administered in specialized clinics or in the form of esketamine (a nasal spray approved by the FDA). Advocates have touted its low risk of respiratory depression compared to classic opioids. However, concerns about its abuse potential have persisted, and this study may add weight to calls for more careful prescribing.
Critics of the research note that ketamine’s clinical effects—particularly its antidepressant action—may still rely heavily on NMDA receptor pathways. They argue that opioid receptor activation could explain side effects like sedation and euphoria but is not necessarily responsible for its therapeutic benefits in depression.
The study’s authors recommend further research into whether ketamine’s opioid activity contributes to its antidepressant effects, and whether long-term use could lead to opioid-type dependence or tolerance. They also suggest that patients receiving ketamine therapy should be monitored for signs of opioid misuse or withdrawal.