Selective review and commentary on emerging pharmacotherapies for opioid addiction

A Novel Maintenance Therapeutic for Opioid Use Disorder

Opioid use disorder (OUD) is a major socioeconomic burden. An ideal OUD pharmacotherapy will mitigate the suffering associated with opioid-withdrawal, inhibit the effects of high efficacy opioids, and minimize opioid-cravings while being safe and accessible to a diverse patient population. Although current OUD pharmacotherapies inhibit the euphoric effects of opioids of abuse, the extent to which they safely alleviate withdrawal and opioid-cravings corresponds with their intrinsic µ opioid receptor (MOR) efficacy. In addition to inhibiting the euphoric effects of opioids of abuse, the medium efficacy MOR agonist buprenorphine alleviates withdrawal and opioid-cravings, but its intrinsic MOR efficacy is sufficient such that its utility is limited by abuse and safety liabilities. Although the MOR antagonist naltrexone minimizes euphoria and has no abuse liability, it exacerbates suffering associated with withdrawal and opioid cravings. Therefore, a therapeutic with intrinsic MOR activity between the partial agonist (buprenorphine) and the antagonist (naltrexone) would strike a balance between the benefits and liabilities of these two therapeutics. To address this need, we derived RM1490, an MOR agonist based on a nonmorphinan scaffold that exhibits approximately half the intrinsic MOR efficacy of buprenorphine. In a series of preclinical assays, we compared RM1490 with buprenorphine and naltrexone at doses that achieve therapeutic levels of central nervous system MOR occupancy. RM1490 exhibited a behavioral profile consistent with reduced reward, dependence, and precipitated withdrawal liabilities. RM1490 was also more effective than buprenorphine at reversing the respiratory depressant effects of fentanyl and did not suppress respiration when combined with diazepam. SIGNIFICANCE STATEMENT: In preclinical studies, RM1490 has a physiological and behavioral profile suitable for opioid use disorder maintenance therapy.

Patients' perspectives on initiating treatment with extended-release naltrexone (XR-NTX)

BACKGROUND

The National Drug Abuse Treatment Clinical Trials Network (CTN) multisite comparative-effectiveness study ("X:BOT") by Lee et al. (2018) found that, once initiated, extended-release naltrexone (XR-NTX) is as similarly safe and effective as sublingual buprenorphine-naloxone (BUP-NX) for the treatment of opioid use disorder (OUD). However, the detoxification hurdle makes XR-NTX much more difficult to initiate than BUP-NX. This hurdle highlights the need to better understand how patients transition from active opioid use to XR-NTX treatment.

OBJECTIVE

To explore patient-identified barriers and facilitators to initiating antagonist treatment (XR-NTX) within the context of an inpatient hospital setting and to reflect postdischarge experiences of those who did and did not initiate XR-NTX treatment.

METHOD

We used a convenience sampling strategy to identify study candidates, with the intention of recruiting approximately an equal number of medication-initiated and noninitiated patients. Study participants (N = 14) included 13 males and 1 female with OUD randomized to the XR-NTX arm of the X:BOT study at 1 of the 8 study sites. Seven participants in this sample initiated XR-NTX treatment, and seven did not. Each participant completed one semistructured qualitative interview. We analyzed transcripts using deductive and inductive approaches to conventional content analysis.

RESULTS

Although the majority of participants viewed opioid blockade, once-monthly dosing, and no dependence or withdrawal as favorable attributes of XR-NTX, participant ambivalence and lack of familiarity with antagonist treatment were barriers to treatment initiation. The long duration of action and the perceived "commitment" to the medication (e.g., "At the time, a month sounded like a year") compounded the patients' concerns and ambivalence. The majority of those who initiated XR-NTX described it as an effective treatment for OUD, with treatment satisfaction and sustained abstinence emerging as central themes among this population. Some participants who did not successfully initiate XR-NTX expressed regret and a willingness to try XR-NTX in the future.

CONCLUSION

Achieving full opioid detoxification is one, but not the only, barrier to initiating treatment with XR-NTX. Additional participant-identified barriers to XR-NTX initiation include fears and ambivalence regarding antagonist treatment. Once initiated, participants perceive XR-NTX to be an effective treatment for maintaining abstinence from opioids. XR-NTX appealed to participants due to the autonomy it affords with once-monthly dosing and no physical dependence.

Clinical Trials for Opioid Use Disorder

This chapter describes recent clinical trials for opioid use disorder (OUD), an area that has rapidly accelerated in response to the opioid overdose crisis in the USA and newly appropriated funding. Trials involve a wide range of compounds including cannabinoids and psychedelics, new and existing compounds targeting domains emerging from addiction neuroscience, agents repurposed from other indications, and novel strategies including vaccines, enzymes, and other biologicals. In parallel, new formulations of existing compounds offer immediate promise, as do a variety of web-based interventions and smartphone-delivered apps. Trials focused on implementing existing effective interventions in mainstream healthcare settings, and others focused on special populations, e.g., adolescents, criminal justice, pregnant women, native Americans, etc., have the potential to vastly expand treatment in the near term. Given the range of ongoing and recent trials, this chapter is not intended to be an exhaustive review but rather to present an overview of approaches within the framework of the opioid treatment cascade and the context of current OUD pharmacotherapies.

Using nominal group technique to identify barriers, facilitators, and preferences among patients seeking treatment for opioid use disorder: A needs assessment for decision making support

BACKGROUND

The opioid crisis requires rapid scale-up of evidence-based interventions to treat opioid use disorder (OUD), of which pharmacologic therapies with methadone, buprenorphine or long-acting naltrexone are most effective. With recently-developed formulations, there are unprecedented treatment options. Even when pharmacologic treatment is accessible, however, uptake remains low, suggesting individual-level barriers. Decision aids are an evidence-based strategy that may overcome these barriers. This study aims to inform such a tool by describing and rank-ordering patients' considerations when deciding whether to start medication and, if starting, choosing a medication.

METHODS

Adults with OUD (N = 81) attending an addiction treatment center or syringe exchange program completed focus groups using nominal group technique, a consensus method that generates and ranks response. The qualitative component generates a broad array of responses, followed by rank-ordering to prioritize responses. Responses to questions about starting any medications and the pros and cons of five specific medications were ranked and coded.

RESULTS

The decision to initiate pharmacologic therapy and choose among medications was influenced by six key attributes in decreasing priority: (1) benefits, (2) side effects of treatment, (3) medication delivery strategies, (4) convenience, (5) how expectations for treatment are met, and (6) how medication (especially methadone) can represents trading one addiction for another.

CONCLUSIONS

Pharmacologic properties, logistical factors, and managing expectations were important themes in decision-making for starting, choosing, and staying on medications, and to a lesser degree, negative views about medications, specifically OAT, as an addiction itself. Desire for more control over treatment persisted in all themes. This study identified specific knowledge gaps, expectations, and priorities which are important for developing a decision aid for OUD treatment relevant to the target group. Nominal group technique is an established mixed-methodology that we have applied to a new population and purpose, that of conducting needs assessment for decision aid development.

Lofexidine versus diazepam for the treatment of opioid withdrawal syndrome: A double-blind randomized clinical trial in Singapore

BACKGROUND

Many individuals leave costly inpatient detoxification programs prematurely because of the severity of withdrawal symptoms experienced. In the absence of opioid-assisted detoxification in Singapore, diazepam is used to manage withdrawal. However since diazepam is addictive, there is a need to explore the effectiveness of alternative medications.

DESIGN AND PROCEDURES

The study aimed to examine the safety and efficacy of lofexidine, a non-opiate, non-addictive, alpha 2-adrenergic agonist in assisting opioid detoxification in Singapore, using a randomized, double-blind, investigator-initiated placebo-controlled trial comparing lofexidine against diazepam. Opioid dependent patients (n = 111) were randomized to receive a 10-day course of lofexidine (n = 56) or diazepam (n = 55). The primary endpoint was the Objective Opioid Withdrawal Scale (OOWS) score on days 3 and 4 and secondary outcomes were the Short Opioid Withdrawal Scale (SOWS) score, program retention rate, and ratings of opiate craving.

MAIN FINDINGS

The OOWS, SOWS and opiate craving scores were consistently lower in the lofexidine group relative to the diazepam group over the 14-day study period; however no statistically significant differences were found on days 3 and 4 (peak withdrawal). Changes in mean pupil size during peak withdrawal were significantly smaller in the lofexidine group and more participants in the lofexidine group remained in treatment and completed detoxification.

CONCLUSIONS

Lofexidine was at least as effective as diazepam in reducing the opioid withdrawal syndrome and increased treatment retention. In addition to its non-addictive and non-abuse properties, lofexidine has several clinical advantages over diazepam. The use of lofexidine is recommended when opioid-assisted medications are not available.

Probuphine® (buprenorphine implant): a promising candidate in opioid dependence

Opioid dependence leads to physical dependence and addiction which finally results in profound medical, psychological and social dysfunction. One of the useful medications for opioid dependence is buprenorphine, the partial opioid agonist, which is used alone or in combination with naloxone. However, buprenorphine is the victim of its own success due to its illicit use and accidental poisoning in children. Also, buprenorphine typically requires daily self-administration and its effectiveness heavily depends on patient adherence. So, poor treatment adherence results in ineffective treatment manifesting as craving and withdrawal symptoms. Short-term use of buprenorphine in opioid dependence is also often followed by relapse. Buprenorphine when used sublingually often results in inadequate or fluctuating blood concentrations and poorer treatment retention compared with methadone. All of these led to the development of Probuphine®, a polymeric matrix composed of ethylene vinyl acetate and buprenorphine in the form of implants, that are implanted subdermally in office practice and deliver the active drug over 6 months. Buprenorphine release from such implant is fairly consistent, avoiding plasma peaks and troughs, and the implant is also reported to be safe. In this review article, we have highlighted these aspects of treatment of opioid addiction, stressing on the pharmacology of buprenorphine and Probuphine®, and relevant clinical trials addressing the efficacy and safety of Probuphine®. This sustained-release implantable formulation of buprenorphine has the potential to be a suitable alternative to daily or alternate day sublingual buprenorphine which can thereby eliminate the need for daily supervision, minimizing fluctuations in plasma concentrations, and allowing these patients to reduce clinic or pharmacy visits.

Buprenorphine in the treatment of opioid addiction: opportunities, challenges and strategies

INTRODUCTION

Buprenorphine follows the success of methadone as another milestone in the history of treatment for opioid addiction. Buprenorphine can be used in an office-based setting where it is clearly effective, highly accepted by patients and has a favorable safety profile and less abuse potential. However, the adoption of buprenorphine treatment has been slow in the USA.

AREAS COVERED

This article first reviews the history of medication-assisted opioid addiction treatment and the current epidemic opioid addiction, followed by a review of the efficacy, pharmacology and clinical prescription of buprenorphine in office-based care. We then explore the possible barriers in using buprenorphine and the ways to overcome these barriers, including new formulations, educational programs and policy regulations that strike a balance between accessibility and reducing diversion.

EXPERT OPINION

Buprenorphine can align addiction treatment with treatments for other chronic medical illnesses. However, preventing diversion will require graduate and continuing medical education and integrated care models for delivery of buprenorphine to those in need.

Electronic health records: essential tools in integrating substance abuse treatment with primary care

While substance use problems are considered to be common in medical settings, they are not systematically assessed and diagnosed for treatment management. Research data suggest that the majority of individuals with a substance use disorder either do not use treatment or delay treatment-seeking for over a decade. The separation of substance abuse services from mainstream medical care and a lack of preventive services for substance abuse in primary care can contribute to under-detection of substance use problems. When fully enacted in 2014, the Patient Protection and Affordable Care Act 2010 will address these barriers by supporting preventive services for substance abuse (screening, counseling) and integration of substance abuse care with primary care. One key factor that can help to achieve this goal is to incorporate the standardized screeners or common data elements for substance use and related disorders into the electronic health records (EHR) system in the health care setting. Incentives for care providers to adopt an EHR system for meaningful use are part of the Health Information Technology for Economic and Clinical Health Act 2009. This commentary focuses on recent evidence about routine screening and intervention for alcohol/drug use and related disorders in primary care. Federal efforts in developing common data elements for use as screeners for substance use and related disorders are described. A pressing need for empirical data on screening, brief intervention, and referral to treatment (SBIRT) for drug-related disorders to inform SBIRT and related EHR efforts is highlighted.