Lofexidine in Combination With Oral Naltrexone for Opioid Use Disorder Relapse Prevention: A Pilot Randomized, Double-Blind, Placebo-Controlled Study

Adrenoceptors: A Focus on Psychiatric Disorders and Their Treatments

Research into the involvement of adrenoceptor subtypes in the cause(s) of psychiatric disorders is particularly challenging. This is partly because of difficulties in developing animal models that recapitulate the human condition but also because no evidence for any causal links has emerged from studies of patients. These, and other obstacles, are outlined in this chapter. Nevertheless, many drugs that are used to treat psychiatric disorders bind to adrenoceptors to some extent. Direct or indirect modulation of the function of specific adrenoceptor subtypes mediates all or part of the therapeutic actions of drugs in various psychiatric disorders. On the other hand, interactions with central or peripheral adrenoceptors can also explain their side effects. This chapter discusses both aspects of the field, focusing on disorders that are prevalent: depression, schizophrenia, anxiety, attention-deficit hyperactivity disorder, binge-eating disorder, and substance use disorder. In so doing, we highlight some unanswered questions that need to be resolved before it will be feasible to explain how changes in the function of any adrenoceptor subtype affect mood and behavior in humans and other animals.

Managing Opioid Withdrawal in an Outpatient Setting With Lofexidine or Clonidine

Background

There is a need for improved strategies for managing abrupt opioid withdrawal when transitioning patients with opioid use disorder to comprehensive longitudinal care strategies such as naltrexone maintenance treatment. In addition, alpha-2 adrenergic agonists are used to ameliorate withdrawal symptoms, but current data characterizing real-world treatment are lacking.

Methods

A retrospective chart review was conducted in outpatients undergoing abrupt opioid withdrawal managed with lofexidine (0.18 mg, 1-4 tablets 4x daily for 7 days, pro re nata [PRN or as needed]) or clonidine (0.2 mg, 1 tablet 3x daily for 10 days, PRN). Withdrawal outcomes were characterized at 30 days of follow-up. Binomial logistic regression was used to assess a potential association of the two treatments with different likelihoods of opioid cessation success in this real-world outpatient practice.

Results

In cases treated with lofexidine (n=166) and clonidine (n=432), respectively, 40% and 10% were opioid-free, 6% and 2% continued long-term buprenorphine or methadone, 17% and 36% relapsed, and 37% and 52% were lost to follow-up at 30 days post-withdrawal. Among patients returning for follow-up care, 63% of patients treated with lofexidine and 21% treated with clonidine were opioid-free. Lofexidine was associated with a higher likelihood of opioid cessation success relative to clonidine (OR=6.47; Wald Chi-square=53.79, p<0.001).

Conclusion

Among outpatients returning for follow-up care, nearly two-thirds of those managed with lofexidine reached opioid-free status at 30 days post-withdrawal, which was a higher likelihood than those managed with clonidine, thus allowing their transition to comprehensive care, including naltrexone.

Complex Interactions Between Sex and Stress on Heroin Seeking

Rationale: Stress plays a dual role in substance use disorders as a precursor to drug intake and a relapse precipitant. With heroin use at epidemic proportions in the United States, understanding interactions between stress disorders and opioid use disorder is vital and will aid in treatment of these frequently comorbid conditions. Objectives: Here, we combine assays of stress and contingent heroin self-administration (SA) to study behavioral adaptations in response to stress and heroin associated cues in male and female rats. Methods: Rats underwent acute restraint stress paired with an odor stimulus and heroin SA for subsequent analysis of stress and heroin cue reactivity. Lofexidine was administered during heroin SA and reinstatement testing to evaluate its therapeutic potential. Rats also underwent tests on the elevated plus maze, locomotor activity in a novel environment, and object recognition memory following stress and/or heroin. Results: A history of stress and heroin resulted in disrupted behavior on multiple levels. Stress rats avoided the stress conditioned stimulus and reinstated heroin seeking in response to it, with males reinstating to a greater extent than females. Lofexidine decreased heroin intake, reinstatement, and motor activity. Previous heroin exposure increased time spent in the closed arms of an elevated plus maze, activity in a round novel field, and resulted in object recognition memory deficits. Discussion: These studies report that a history of stress and heroin results in maladaptive coping strategies and suggests a need for future studies seeking to understand circuits recruited in this pathology and eventually help develop therapeutic approaches.

Functional observation after morphine withdrawal: effects of SJP-005

RATIONALE AND OBJECTIVE

SJP-005 (ketotifen and ibuprofen) is being developed as a potential new treatment for opioid withdrawal. Three studies were conducted to evaluate the early phase (acute, day 1) and late phase (days 2-12) effects of SJP-005 on discontinuation-induced morphine withdrawal.

METHODS

Sprague-Dawley rats received subcutaneous morphine twice daily for 18 days and ceased on day 19. Twice daily, oral dosages of placebo or SJP-005 (1 mg/kg ketotifen and 15 mg/kg ibuprofen) were administered starting 4 days before (study 1), 2 days before (study 2), or immediately after (study 3) morphine cessation. Functional observations were made up to 12 h after treatment cessation on day 19 (early phase), and immediately after treatment on days 20-30 (late phase). Treatment effects (mean overall score, and individual symptoms) were compared with placebo using ANOVA, and Tukey's tests in case of multiple comparisons.

RESULTS

Across the studies, the number of withdrawal signs on day 19 (early phase) and days 20-30 (late phase) was lower with SJP-005 compared with placebo. The effects of SJP-005 when treatment was initiated 2 days before morphine cessation by discontinuation were most pronounced and statistically significant in the late phase (F_(1,18) = 14.10, p = 0.001). In particular, a significant reduction was observed in hypersensitivity to touch (F_(1,18) = 13.65, p = 0.002). A 50% reduction in withdrawal symptoms was observed 9.0 days after placebo versus 4.5 days after SJP-005. After 9.0 days, all withdrawal symptoms were absent in the SJP-005 group, while symptoms in the placebo group were still evident on day 18.

CONCLUSION

Compared to placebo, SJP-005 significantly reduced the incidence and duration of discontinuation-induced morphine withdrawal symptoms when treatment was initiated 2 days before morphine cessation.

Monitoring and Improving Naltrexone Adherence in Patients with Substance Use Disorder

OBJECTIVE

Naltrexone is an opioid antagonist used for the treatment of patients with opioid use disorder and alcohol use disorder. This population often presents problems of follow-up and therapeutic efficacy related to adherence to treatment. The purpose of our study is to provide an exhaustive summary of the current evidence regarding naltrexone adherence in people with substance use disorders and to identify possible variables that may influence adherence to naltrexone.

METHODS

Two searches were performed in bibliographic databases (PubMed, Embase), and studies included in the systematic review were those published from January 1, 2011 to September 2020, with participants over 18 years of age, evaluating treatment with naltrexone in alcohol use disorder and opioid use disorder. From the total of 133 articles initially selected, 36 were included and analyzed in the systematic review.

RESULTS

Naltrexone has not demonstrated superiority over other available treatments in terms of adherence and abstinence, although reinforcement systems have obtained favorable results as an additional strategy to improve adherence.

CONCLUSION

It is necessary to study other psychosocial variables involved in improving adherence, in addition to taking patient preferences into account in order to improve the external validity of the results.