Threshold period
INOT did not induce ≥ 3 weeks of continuous abstinence. However, beginning with week 3, the odds of weekly abstinence increased dramatically in the INOT group, from 4.61 (95% confidence interval,1.05, 20.3) to 15.0 (1.18, 190.2) by week 6 (t = 2.12, P = .037).
The overall medication group by time interaction across all 6 weeks was not significant (F1,69 = 1.73, P = .19); but when the interaction was removed, the difference between the overall effect of medication (INOT vs. placebo) over all 6 weeks “reached trend-level significance” (F1,70) = 3.42, P = .07).
The subjective rating outcomes (cravings, perceived stress, cocaine dependence, and depression) “did not show a significant medication group by time interaction effect,” the authors reported, although stress-induced cravings did tend toward a significant difference between the groups.
Half of the patients did not complete the full 6 weeks. Of those who discontinued, 85% came from the INOT group and 15% from the placebo group. Of the 11 who dropped out from the treatment group, seven were abstinent at the time of discontinuation for ≥ 1 week.
There were no significant differences in rates of reported side effects between the two groups.
“This study highlights some promise that perhaps there is a threshold period of time you need to cross, after which time oxytocin could really be really helpful as acute or maintenance medication,” said Dr. Raby. The short study duration might have been a disadvantage. “We might have seen better results if the study had been 8 or 12 weeks in duration.”
Using motivational approaches during the early phase – e.g., psychotherapy or a voucher system – might increase adherence, and then “after this initial lag, we might see a more therapeutic effect,” he suggested.
Dr. Raby noted that his group studied stress hormone secretions in the cocaine-dependent study participants during the 7-day induction period and that the findings, when published, could shed light on this latency period. “Cocaine dependence creates adaptations in the stress system,” he said.
‘Nice first step’
Commenting on the study, Jane Joseph, PhD, professor in the department of neurosciences and director of the neuroimaging division at Medical University of South Carolina, Charleston, said it is “nice to see a clinical trial using oxytocin in cocaine dependence [because] preclinical research has shown fairly convincing effects of oxytocin in reducing craving or stress in the context of cocaine seeking, but findings are rather mixed in human studies.”
Dr. Joseph, who was not involved with the study, said her group’s research showed oxytocin to be the most helpful for men with cocaine use disorder who reported childhood trauma, while for women, oxytocin “seemed to worsen their reactivity to cocaine cues.”
She said the current study is a “nice first step” and suggested that future research should include larger sample sizes to “address some of the individual variability in the response to oxytocin by examining sex differences or trauma history.”
The study was supported by an award from the National Institute of Drug Abuse. Dr. Raby and coauthors and Dr. Joseph have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.