Effects of ketamine treatment on cocaine-induced reinstatement and disruption of functional connectivity in unanesthetized rhesus monkeys

The effects of (2R,6R)-hydroxynorketamine on oxycodone withdrawal and reinstatement

Despite the thousands of lives lost during the ongoing opioid crisis, a scarcity of new and effective clinical treatments for opioid use disorder (OUD) remains. To address this unmet need, some researchers have turned to dissociative and psychedelic drugs to treat multiple psychiatric conditions. In particular, low doses of ketamine have been shown to attenuate opioid withdrawal and drug use in clinical and preclinical studies. However, ketamine has misuse liability and dissociative side effects that may limit its widespread application as a treatment for OUD. More recently, (2R,6R)-hydroxynorketamine (HNK), a ketamine metabolite that lacks misuse potential, has gained attention for its effectiveness in depression and stress models. To uncover its role in OUD, we tested the time-dependent effects of (2R,6R)-HNK on oxycodone withdrawal and reinstatement of oxycodone conditioned place preference (CPP). In male and female oxycodone-dependent mice, we found that 24h pretreatment with (2R,6R)-HNK (10 or 30mg/kg, s.c.) reduced the frequency of withdrawal-like behaviors and global withdrawal scores during naloxone-precipitated withdrawal, whereas 1h pretreatment with (2R,6R)-HNK only reduced paw tremors and the sum of global withdrawal scores but not GWS Z-scores. In other experiments, both 1h and 24h pretreatment with (2R,6R)-HNK (30mg/kg, s.c.) blocked drug-induced reinstatement of oxycodone CPP. Finally, we found (2R,6R)-HNK (30mg/kg, sc) had no effect on locomotor activity and thigmotaxis. Together, these results indicate that acute (2R,6R)-HNK has efficacy in some preclinical models of OUD without producing locomotor or anxiety-like side effects.

Mystical-type experiences occasioned by ketamine mediate its impact on at-risk drinking: Results from a randomized, controlled trial

BACKGROUND

Sub-anesthetic ketamine administration may be helpful for substance use disorders. Converging evidence suggests that the efficacy of ketamine for certain conditions may implicate a subset of its psychoactive effects.

AIMS

The aim of this analysis is to evaluate whether the mystical-type effects of ketamine are critical for clinical efficacy in alcohol-dependent individuals. In this secondary analysis, we determine if a subset of the psychoactive effects of ketamine, the so-called mystical-type experience, mediates the effect of ketamine, when combined with motivational enhancement therapy, on at-risk drinking behavior in alcohol-dependent individuals interested in treatment.

METHODS

Forty alcohol dependent adults were randomized to either a 52-minute infusion of ketamine or midazolam, which they received on a designated quit-day during the second week of a five-week motivational enhancement therapy regimen. Psychoactive effects were assessed following the infusion, and alcohol use was monitored for the subsequent 3 weeks at each twice-weekly visit.

RESULTS

We found that ketamine leads to significantly greater mystical-type effects (by Hood Mysticism Scale) and dissociation (by Clinician Administered Dissociative States Scale) compared to the active control. Ketamine also led to significant reduction in at-risk drinking. The Hood Mysticism Scale, but not Clinician Administered Dissociative States Scale score, was found to mediate the effect of ketamine on drinking behavior.

CONCLUSIONS

This trial adds evidence to the literature on the importance of mystical-type experiences in addiction treatment. Future research should continue to investigate the relationship between the psychoactive effects of psychedelic therapeutics and clinical outcomes for other substance use and mental health disorders.

A Single Ketamine Infusion Combined With Motivational Enhancement Therapy for Alcohol Use Disorder: A Randomized Midazolam-Controlled Pilot Trial

OBJECTIVE

Pharmacotherapy and behavioral treatments for alcohol use disorder are limited in their effectiveness, and new treatments with innovative mechanisms would be valuable. In this pilot study, the authors tested whether a single subanesthetic infusion of ketamine administered to adults with alcohol dependence and engaged in motivational enhancement therapy affects drinking outcomes.

METHODS

Participants were randomly assigned to a 52-minute intravenous administration of ketamine (0.71 mg/kg, N=17) or the active control midazolam (0.025 mg/kg, N=23), provided during the second week of a 5-week outpatient regimen of motivational enhancement therapy. Alcohol use following the infusion was assessed with timeline followback method, with abstinence confirmed by urine ethyl glucuronide testing. A longitudinal logistic mixed-effects model was used to model daily abstinence from alcohol over the 21 days after ketamine infusion.

RESULTS

Participants (N=40) were mostly middle-aged (mean age=53 years [SD=9.8]), predominantly white (70.3%), and largely employed (71.8%) and consumed an average of five drinks per day prior to entering the study. Ketamine significantly increased the likelihood of abstinence, delayed the time to relapse, and reduced the likelihood of heavy drinking days compared with midazolam. Infusions were well tolerated, with no participants removed from the study as a result of adverse events.

CONCLUSIONS

A single ketamine infusion was found to improve measures of drinking in persons with alcohol dependence engaged in motivational enhancement therapy. These preliminary data suggest new directions in integrated pharmacotherapy-behavioral treatments for alcohol use disorder. Further research is needed to replicate these promising results in a larger sample.