A tale of 2 ADFs: differences in the effectiveness of abuse-deterrent formulations of oxymorphone and oxycodone extended-release drugs

Oxymorphone and Oxycodone Pharmacy Purchases in US Counties: Prelude to the Largest Rural Human Immunodeficiency Virus Outbreak in US History

PURPOSE

The largest rural outbreak of human immunodeficiency virus (HIV) in the US was centered in Scott County, Indiana, and linked to injection practices involving the opioid Opana ER (oxymorphone extended release [ER] reformulated). We examined supply trends using pharmacy transactions of Opana ER in Scott and all US counties from January 2007 to December 2019.

METHODS

We calculated the monthly morphine milligram equivalents (MME) of Opana ER (and its competitor OxyContin) in pharmacies using the Automation of Reports and Consolidated Orders System (ARCOS) database from the Washington Post. We modeled the MME rate per capita in Scott County and five geographic comparators in seven distinct time periods including the market introduction of abuse deterrent formulations of both drugs and the HIV outbreak period (circa 2014).

RESULTS

After Opana ER introduction, transaction rates surged in Scott County, where annual OxyContin MMEs were already seven-fold higher than Indiana overall (CY2009: 46.8 vs. 6.8 MME/pop., respectively). Immediately after OxyContin's reformulation, the Opana ER growth rate in Scott County surpassed all geographic comparators modeled (~27 times faster than the US, 1.28 vs. 0.047 MME/pop/month, respectively). By 2012, prior to the outbreak, MMEs from Opana ER almost perfectly replaced the diminishing OxyContin supply. When Opana ER with INTAC was subsequently introduced, pharmacy transactions declined precipitously by nearly 50%, persisting through the HIV outbreak period and market withdrawal.

CONCLUSIONS

Opana ER rapidly supplanted OxyContin in a vulnerable population that was at heightened risk for HIV who subsequently faced an immediate supply shock after its reformulation. Pharmacy transactions are critical for suspicious order monitoring and pharmacovigilance by US and international agencies especially during deleterious supply shocks in legal and illicit drug markets.

A Cross-Sectional Study of Tampering in Xtampza ER, an Abuse-Deterrent Formulation of an Extended-Release Opioid, in a Treatment Center Population

BACKGROUND AND OBJECTIVE

While the current landscape of opioid use disorder (OUD) is complicated by the increase in use of non-prescription opioids, prescription opioids continue to be frequently used in non-medical ways. In response to this abuse, pharmaceutical companies have developed abuse deterrent formulations (ADFs) for extended-release (ER) opioids. To test the effectiveness of Xtampza ER ADF (oxycodone myristate) at reducing tampering, its rate of tampering in a treatment-center population was compared to immediate release (IR) single entity (SE) oxycodone, other ER oxycodone opioids, and ER oxymorphone.

METHODS

Data were collected between the third quarter of 2018 and the third quarter of 2021 from individuals entering nationally distributed opioid treatment programs. To determine odds of tampering with Xtampza ER compared to each comparator, a logistic model was fit with a random intercept allowing for multiple drugs in each subject. Within-subject correlation was assumed to have a compound symmetric relationship.

RESULTS

Overlap among the categories of drug tampering was high. Logistic regression analyses found that oxycodone myristate had lower odds of tampering when compared to both IR SE oxycodone (OR = 0.23 [95% CI 0.11, 0.50], p = 0.0002) and ER oxymorphone (OR = 0.30 [95% CI 0.14, 0.67], p = 0.0038). Oxycodone myristate was not significantly different from other ER oxycodone opioids (OR = 0.5 [95% CI 0.24, 1.03], p = 0.0612). These findings did not change when the estimates were adjusted for age and sex.

CONCLUSIONS

Drugs employing ADF technology may reduce the likelihood of tampering when compared to non-ADF formulations in a treatment-center population, which represents an opportunity for intervention in OUD among those still requiring pain management.

Association between recent overdose and chronic pain among individuals in treatment for opioid use disorder

Chronic pain increases risk for opioid overdose among individuals with opioid use disorder. The purpose of this study is to evaluate the relationship between recent overdose and whether or not chronic pain is active. 3,577 individuals in treatment for opioid use disorder in 2017 or 2018 were surveyed regarding recent overdoses and chronic pain. Demographics from the 2017 Treatment Episode Data Set, which includes all U.S. facilities licensed or certified to provide substance use care, were used to evaluate the generalizability of the sample. χ2 tests and logistic regression models were used to compare associations between recent overdoses and chronic pain. Specifically, active chronic pain was associated with opioid overdose among people in treatment for opioid use disorder. Individuals with active chronic pain were more likely to have had a past month opioid overdose than those with no history chronic pain (adjusted OR = 1.55, 95% CI 1.16-2.08, p = 0.0003). In contrast, individuals with prior chronic pain, but no symptoms in the past 30 days, had a risk of past month opioid overdose similar to those with no history of chronic pain (adjusted OR = 0.88, 95% CI 0.66-1.17, p = 0.38). This suggests that the incorporation of treatment for chronic pain into treatment for opioid use disorder may reduce opioid overdoses.

An Evaluation of the Effect of the OxyContin Reformulation on Unintentional Fatal and Nonfatal Overdose

OBJECTIVES

OxyContin was reformulated with a polyethylene oxide matrix in August 2010 to reduce the potential for intravenous abuse and for abuse by insufflation. The objective of this study was to evaluate the impact of OxyContin's reformulation on overdose (OD) risk for individuals dispensed OxyContin in comparison to those dispensed other opioids under regular care.

MATERIALS AND METHODS

Three national insurance databases with National Death Index linkage identified OD in individuals with any dispensing of OxyContin or a primary comparator opioid (extended release morphine, transdermal fentanyl, or methadone) between July 2008 through September 2015. A difference-in-differences design was used to compare the pre-post reformulation changes in OD rates for OxyContin versus comparators.

RESULTS

A total of 297,836 individuals were dispensed OxyContin and 659,673 individuals were dispensed a primary comparator across the 3 databases. Overall, there was little or no difference in the temporal change in OD incidence in comparators versus OxyContin (Medicaid: adjusted ratio-of-rate-ratios (aRoRs) ranging from 0.90 to 1.05; MarketScan/HIRD: aRoR ranging from 1.10 to 1.22). However, restriction to person-time without concomitant opioid use revealed a modestly greater reduction in OD incidence over time during OxyContin use, as the aRoRs comparing the primary comparators to OxyContin ranged from 1.06 to 1.30 in Medicaid and from 1.64 to 1.85 in MarketScan/HIRD.

DISCUSSION

This study did not detect an overall effect of the OxyContin reformulation on OD in insured patients under regular medical care. There is a suggestion of a modestly reduced OxyContin-associated OD risk following the reformulation but only in commercially insured individuals receiving single-opioid regimens.

A 13-Year National Monitoring Study to Assess Narcotic Prescriptions and Indications (2007-2019)

INTRODUCTION

Analgesics are among the most widely used drugs worldwide. This study describes the population treated with narcotic analgesics, their therapeutic indications and how the data have evolved over a decade.

METHODS

A cross-sectional, national, multicentre survey study was conducted that included surveys taken every year from 2007 to 2019 in a national sample of 1500 randomly selected dispensing pharmacies.

RESULTS

The mean age of patients, mostly women (around 60%), remained stable over the study period (63.2 ± 17.1 years in 2007, 68.2 ± 17.2 years in 2019). The proportion of patients treated for more than 3 months increased from 2007 to 2019. Most prescriptions involved morphine, oxycodone and fentanyl (98.5% of all prescriptions in 2019). Morphine prescriptions dropped dramatically from 49.6% (2007) to 32.3% (2019) of the total narcotic analgesics. Fentanyl prescriptions varied from 40.1% in 2007 to 32.2% in 2019. Prescriptions of oxycodone, regardless of the indication, increased steadily from 2007, from 8.3 to 34% in 2019, becoming the most prescribed narcotic analgesic for the first time since the beginning of the survey.

CONCLUSIONS

This study demonstrates how narcotic opioids are prescribed, thanks to the active participation of health professionals, and confirms the striking increase in the prescription of oxycodone.

Abuse-deterrent extended-release oxycodone and risk of opioid-related harm

AIM

To establish and quantify the association between abuse-deterrent formulation (ADF) oxycodone and 1-year risk of opioid-related harm.

DESIGN

Propensity score-matched cohort study of electronic medical records for years 2014-18, with patients followed up for 1 year after their index health-care visit.

SETTING

More than 70 million patients from 56 US health-care organizations.

PARTICIPANTS

Patients aged 18-64 years at index health-care visit with any indication for an oral opioid analgesic, with no past 12-month history of oral oxycodone use or substance use disorder, and who were alive at the end of the 1-year follow-up (new episode of prescription oral ADF oxycodone [OxyContin], n = 45 045; new episode of non-ADF oxycodone opioid preparation, n = 1 377 359).

MEASUREMENTS

International Classification of Diseases diagnoses of any opioid-related disorder or non-fatal opioid poisoning within 1 year of the index health-care visit. Pooled odds ratios (OR) with 95% confidence intervals (95% CI).

FINDINGS

After propensity score matching, 89 802 patients with a mean age of 44 [standard deviation (SD) = 11] years (62% women, 68% white) were included. During 1-year follow-up, 1445 diagnoses of opioid use disorder or opioid poisoning occurred in the ADF oxycodone cohort (34.8/1000 person-years) and 765 occurred in the non-ADF oxycodone cohort (18.2/1000 person-years). The odds of opioid-related adverse outcomes were increased in the ADF oxycodone cohort compared with the non-ADF oxycodone opioid cohort, including for opioid use disorders (OR = 2.02; 95% CI = 1.83, 2.23) and opioid poisoning (OR = 1.64 95% CI = 1.35, 1.99).

CONCLUSIONS

Patients with a new prescription of abuse-deterrent formulation oxycodone may be at increased risk of opioid-related harm.

Relative potency of intravenous oxymorphone compared to other µ opioid agonists in humans - pilot study outcomes

AIMS

Intravenous (IV) misuse of the µ opioid analgesic oxymorphone has caused significant public health harms; however, no controlled data on its IV abuse potential are available. The primary aims of this pilot study were to directly compare IV oxymorphone to IV oxycodone, morphine, and hydromorphone on a subjective measure of drug liking and to assess relative potency.

METHODS

Participants (n = 6) with opioid use disorder, physical dependence, and current IV use completed this two-site, within-subject, double-blind, placebo-controlled, inpatient pilot study. During each session, one IV dose (mg/70 kg) was administered: oxymorphone (1.8, 3.2, 5.6, 10, 18, 32), hydromorphone (1.8, 3.2, 5.6, 10, 18), oxycodone (18, 32, 56), morphine (18, 32), and placebo. Data were collected before and for 6 h after dosing. Primary outcomes included safety/physiological effects, subjective reports of drug liking, and relative potency estimates.

RESULTS

All active test drugs produced prototypical, dose-related µ opioid agonist effects (e.g., miosis). Oxymorphone was more potent than the comparator opioids on several measures, including drug liking and respiratory depression (p < 0.05). Across abuse-related subjective outcomes, oxymorphone was 2.3-2.8-fold more potent than hydromorphone and 12.5-14-fold more potent than oxycodone (p < 0.05).

CONCLUSIONS

Despite the relatively small sample size, this pilot study detected robust oxymorphone effects. Oxymorphone was far more potent than the comparator opioids, particularly on abuse potential outcomes. Overall, these findings may help explain surveillance reports that demonstrate, after adjusting for prescription availability, oxymorphone is injected at the highest frequency, relative to other prescription opioids.

Postmarketing Analysis of Misuse, Abuse, and Diversion of Xtampza ER

Objective

To evaluate abuse, misuse, and diversion of Xtampza ER, an extended-release (ER) abuse-deterrent formulation (ADF) of oxycodone.

Methods

Abuse, misuse, and diversion of Xtampza ER were assessed using Researched Abuse, Diversion and Addiction-Related Surveillance (RADARS) System data sources. Xtampza ER was compared with immediate-release (IR) oxycodone, other ADF ER products combined, and non-ADF ER products combined.

Results

Xtampza ER prescriptions increased 50-fold during the study period. In contrast, cases from poison centers, substance abuse treatment centers, and diversion were infrequent and did not increase. Adjusted for prescriptions dispensed, poison center exposures were greater for IR oxycodone (rate ratio [RR] = 2.3, P = 0.008), other ADF ER opioids (RR = 5.2, P < 0.001), and non-ADF ER opioids (RR = 2.5, P = 0.004) than for Xtampza ER. In Treatment Center Programs Combined, past-month abuse prevalence for other ADF ER opioids (odds ratio [OR] = 7.4, P < 0.001) and non-ADF ER opioids (OR = 2.0, P = 0.002) was greater than Xtampza ER; IR oxycodone was not significantly different (OR = 1.2, P = 0.349). In the Drug Diversion Program, rates for IR oxycodone (RR = 3.7, P = 0.003), other ADF ER opioids (RR = 4.2, P = 0.002), and non-ADF ER opioids (RR = 3.4, P = 0.007) were greater than Xtampza ER. Adjustment using morphine equivalents provided similar results, except that IR oxycodone in Treatment Center Programs Combined became higher than Xtampza ER. Nonoral abuse cases involving Xtampza ER were infrequent; Web monitoring data support findings that Xtampza ER is difficult to abuse nonorally.

Conclusion

Xtampza ER abuse, misuse, and diversion and tampering are low relative to other prescription opioid analgesics. Abuse and diversion did not increase over the study period.

Ten-year trend of opioid and nonopioid analgesic use in the French adult population

AIMS

Analgesics are the most widely used medicines worldwide. In parallel, opioid abuse has increased and is of major concern. The accessibility of pharmacologically powerful medicines and the addictovigilance signals in France about the risk of opiates addiction call for an overview of analgesic use. The objective of this study was to investigate the use of analgesics reimbursed in France over a 10-year period through its prevalence.

METHODS

A cross-sectional study repeated yearly was conducted by using data from the French reimbursement database from 2006 to 2015. Analgesics were classified according to their pharmacological potency: prevalence of use for each category and sociodemographic characteristics of patients treated were analysed.

RESULTS

The annual prevalence of analgesic use was high and increased during the study period (59.8%, 253 976 users in 2015). In 2015, prevalence was always higher in women and increased with age, except for those older than 84 years. Peripheral analgesics were the most used (55.3%, 234 739 users). The prevalence of weak analgesic use decreased (21.3%, 90 257 users), mainly due to the definitive withdrawal of dextropropoxyphene in France in 2011, which was not offset by an increase in the consumption of other weak analgesics. For strong analgesics (1.2%, 5129 users), morphine was the most widely used, with a dramatic increase in oxycodone use, especially in the elderly.

CONCLUSION

The prevalence of analgesic use is high: approximately 31 million adults had at least 1 analgesic reimbursed in 2015. The most widely used analgesics were peripheral analgesics, far ahead of opioid analgesics.

Pharmacokinetic and pharmacodynamic considerations in developing a response to the opioid epidemic

Introduction: Opioids continue to be used widely for pain management. Widespread availability of prescription opioids has led to opioid abuse and addiction. Besides steps to reduce inappropriate prescribing, exploiting opioid pharmacology to make their use safer is important.Areas covered: This article discusses the pathology and factors underlying opioid abuse. Pharmacokinetic and pharmacodynamic properties affecting abuse liability of commonly abused opioids have been highlighted. These properties inform the development of ideal abuse deterrent products. Mechanisms and cost-effectiveness of available abuse deterrent products have been reviewed in addition to the pharmacology of medications used to treat addiction.Expert opinion: The opioid crisis presents unique challenges to managing pain effectively given the limited repertoire of strong analgesics. The 5-point strategy to combat the opioid crisis calls for better preventive, treatment, and recovery services, better data, better pain management, better availability of overdose-reversing drugs and better research. There is an urgent need to decrease the cost of abuse deterrent opioids which deters their cost-effectiveness. In addition, discovery of novel analgesics, further insight into central and peripheral pain mechanisms, understanding genomic risk profiles for efficient targeted efforts, and education will be key to winning this fight against the opioid crisis.

Post-marketing studies of pharmaceutical opioid abuse-deterrent formulations: a framework for research design and reporting

BACKGROUND AND AIMS

Opioid formulations with properties to deter abuse (abuse-deterrent formulations; ADFs) have been developed as one response to the prescription opioid 'epidemic'. As for all medicines, ADFs undergo evaluation of safety and efficacy prior to registration for marketing. However, reduced extra-medical use (the primary intended outcome of ADFs and reason for their introduction) can only be established in post-marketing observational studies, comparing them to opioid formulations without abuse-deterrent properties. This has implications for various features of study design and analysis. We discuss proposals for the design, conduct, governance and reporting of post-marketing studies on the effectiveness of pharmaceutical and opioid ADFs.

METHODS

A review of current guidance documents, public work-shops and forums and our own experience with post-marketing studies of ADFs.

RESULTS AND CONCLUSIONS

Research questions for post-marketing studies on ADFs of opioids should reasonably be framed around detecting any probable intended or unintended clinical and/or meaningful changes in specific aspects of extra-medical use (e.g. injection use) and harms. Outcomes reported by prevalence and frequency of occurrence and disaggregated by specific product and route of administration can illustrate the magnitude of ADF impact. We argue that a multi-faceted approach is required, using data from both general population and sentinel high-risk cohorts and from primary and secondary data sources. The comparator (historical non-ADF formulation of that opioid, equivalent current generic or similar opioid product), duration of monitoring and analytical approach require justification and should be sufficient to add weight to conclusions of causality. To maximize transparency, we recommend explicit declarations of funding and conflict of interest, establishment of an advisory committee, publication of study protocol and access to study results.

Mitigation of IV Abuse Through the Use of Abuse-Deterrent Opioid Formulations: An Overview of Current Technologies

Providers who treat patients with chronic pain face a dual challenge: providing adequate access to opioid therapies for appropriate pain management while adopting strategies to minimize the risk for abuse. Commonly prescribed opioids have substantial abuse potential when administered intravenously, and extended‐release (ER)/long‐acting (LA) opioids may be targeted for intravenous (IV) abuse because of the higher per‐dose medication level. The consequences of IV opioid abuse are severe and increase the risks for adverse outcomes, including mortality due to acute health events, serious infections, and deep vein thrombosis, to name a few. To reduce the potential for abuse of prescription opioids by both recreational and experienced drug abusers, abuse‐deterrent formulations (ADFs) of opioid medications employ either physical/chemical barriers or agonist‐antagonist combinations. Here we review the development and use of opioid ADFs as a harm‐reduction strategy, and their potential for mitigating IV opioid abuse. The approved ER/LA opioids with ADF labeling in the United States include formulations of oxycodone, hydrocodone, and morphine. Findings from in vitro laboratory tests of abuse deterrence for opioid ADFs are described herein, as are data from human abuse potential studies for IV abuse of those ADF products, for which such studies are feasible (ie, abuse‐deterrent agonist‐antagonist formulations). The available ADF opioids may decrease both the attractiveness and the feasibility of IV abuse. The adoption of ADF opioids represents one tactic for providing access to needed medication for patients with chronic pain, while potentially reducing the risk for opioid abuse, in a comprehensive effort to combat the opioid epidemic.

Causal inference for evaluating prescription opioid abuse using trend-in-trend design

PURPOSE

One response to the opioid crisis in the United States has been the development of opioid analgesics with properties intended to reduce non-oral use. Previous evaluations of abuse in the community have relied on population averaged interrupted time series Poisson models with utilization offsets. However, competing interventions and secular trends complicate interpretation of time-series analyses. An alternative research design, trend-in-trend, accounts for heterogeneity in per capita opioid dispensing and unmeasured time-varying confounding, which provides a causal evaluation, provided that underlying assumptions are met.

METHODS

Trend-in-trend can be modeled using a logistic regression framework. In logistic regression, exposure was any product-specific outpatient dispensing by three-digit ZIP code and calendar quarter, for 22 opioids. The outcome was any product-specific abuse case ascertained from poison centers and drug treatment programs, covering 94% of the US population, between July 2009 and December 2016. Product-specific odds ratios compared places without dispensing with places with any dispensing; the causal contrast represents the odds of product-specific abuse in the community given exposure.

RESULTS

Dispensing of new and low-volume opioids varied considerably across the country, with no region showing high of all products. Of 22 opioids analyzed, the three with approved labeling as intended to deter abuse ranked near the lowest in both absolute (population-adjusted rates: 1.7, 0.9, and 8.2 per million people per quarter, respectively) and relative measures (trend-in-trend ORs: 1.96, 1.79, 1.69, respectively).

CONCLUSIONS

Postmarketing studies of prescription opioid abuse may benefit by evolving from unadjusted surveillance rates to a causal inference approach.

Doctor shopping of opioid analgesics relative to benzodiazepines: A pharmacoepidemiological study among 11.7 million inhabitants in the French countries

BACKGROUND

The abuse of prescription opioids and its subsequent consequences is an important public concern particularly in the USA. The literature on opioid analgesic abuse is scarce.

OBJECTIVE

We assess the extent and risk of opioid analgesics abuse relative to benzodiazepines (BZD) using the doctor shopping method, taken into account the pharmacological characteristics (dosage, route of administration, extended or immediate release).

METHODS

We used SNIIRAM database covering 11.7 million inhabitants. All individuals with at least one reimbursement for non-injectable opioid analgesic or BZD in 2013 were included. Opioids for mild to moderate pain and for moderately severe to severe pain were studied. The Doctor Shopping Quantity (DSQ) is the quantity obtained by overlapping prescriptions from several prescribers. The Doctor Shopping Indicator (DSI) is the DSQ divided by the total dispensed quantity.

RESULTS

The strong opioid analgesics have the highest DSI (2.79%) versus 2.06% for BZD hypnotics. Flunitrazepam ranked first according to its DSI (13.2%), followed by morphine (4%), and zolpidem (2.2%). The three-strong opioids having the highest DSI were morphine, oxycodone and fentanyl (respectively 4%, 1.7% and 1.5%). The highest DSI was observed for the highest dosages of morphine (DSI = 8.4% for 200 mg) and oxycodone (DSI = 2.8% for 80 mg). The highest DSI for fentanyl was described with nasal and transmucosal forms (4.1% and 3.3% respectively). The highest DSI for morphine was described for extended-release (4.1%).

CONCLUSION

There is a need to reinforce surveillance systems to track opioid misuse and to increase awareness of healthcare professionals.

Multiple injections per injection episode: High-risk injection practice among people who injected pills during the 2015 HIV outbreak in Indiana

BACKGROUND

Misuse of prescription opioid analgesics (POA) has increased dramatically in the US, particularly in non-urban areas. We examined injection practices among persons who inject POA in a rural area that experienced a large HIV outbreak in 2015.

METHODS

Between August-September 2015, 25 persons who injected drugs within the past 12 months were recruited in Scott County, Indiana for a qualitative study. Data from in-depth, semi-structured interviews were analyzed.

RESULTS

All 25 participants were non-Hispanic white and the median age was 33 years (range: 19-57). All had ever injected extended-release oxymorphone (Opana® ER) and most (n=20) described preparing Opana® ER for multiple injections per injection episode (MIPIE). MIPIE comprised 2-4 injections during an injection episode resulting from needing >1mL water to prepare Opana® ER solution using 1mL syringes and the frequent use of "rinse shots." MIPIE occurred up to 10 times/day (totaling 35 injections/day), often in the context of sharing drug and injection equipment.

CONCLUSIONS

We describe a high-risk injection practice that may have contributed to the rapid spread of HIV in this community. Efforts to prevent bloodborne infections among people who inject POA need to assess for MIPIE so that provision of sterile injection equipment and safer injection education addresses the MIPIE risk environment.

Detailed Transmission Network Analysis of a Large Opiate-Driven Outbreak of HIV Infection in the United States

In January 2015, an outbreak of undiagnosed human immunodeficiency virus (HIV) infections among persons who inject drugs (PWID) was recognized in rural Indiana. By September 2016, 205 persons in this community of approximately 4400 had received a diagnosis of HIV infection. We report results of new approaches to analyzing epidemiologic and laboratory data to understand transmission during this outbreak. HIV genetic distances were calculated using the polymerase region. Networks were generated using data about reported high-risk contacts, viral genetic similarity, and their most parsimonious combinations. Sample collection dates and recency assay results were used to infer dates of infection. Epidemiologic and laboratory data each generated large and dense networks. Integration of these data revealed subgroups with epidemiologic and genetic commonalities, one of which appeared to contain the earliest infections. Predicted infection dates suggest that transmission began in 2011, underwent explosive growth in mid-2014, and slowed after the declaration of a public health emergency. Results from this phylodynamic analysis suggest that the majority of infections had likely already occurred when the investigation began and that early transmission may have been associated with sexual activity and injection drug use. Early and sustained efforts are needed to detect infections and prevent or interrupt rapid transmission within networks of uninfected PWID.

Basic/Translational Development of Forthcoming Opioid- and Nonopioid-Targeted Pain Therapeutics

Opioids represent an efficacious therapeutic modality for some, but not all pain states. Singular reliance on opioid therapy for pain management has limitations, and abuse potential has deleterious consequences for patient and society. Our understanding of pain biology has yielded insights and opportunities for alternatives to conventional opioid agonists. The aim is to have efficacious therapies, with acceptable side effect profiles and minimal abuse potential, which is to say an absence of reinforcing activity in the absence of a pain state. The present work provides a nonexclusive overview of current drug targets and potential future directions of research and development. We discuss channel activators and blockers, including sodium channel blockers, potassium channel activators, and calcium channel blockers; glutamate receptor-targeted agents, including N-methyl-D-aspartate, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, and metabotropic receptors. Furthermore, we discuss therapeutics targeted at γ-aminobutyric acid, α2-adrenergic, and opioid receptors. We also considered antagonists of angiotensin 2 and Toll receptors and agonists/antagonists of adenosine, purine receptors, and cannabinoids. Novel targets considered are those focusing on lipid mediators and anti-inflammatory cytokines. Of interest is development of novel targeting strategies, which produce long-term alterations in pain signaling, including viral transfection and toxins. We consider issues in the development of druggable molecules, including preclinical screening. While there are examples of successful translation, mechanistically promising preclinical candidates may unexpectedly fail during clinical trials because the preclinical models may not recapitulate the particular human pain condition being addressed. Molecular target characterization can diminish the disconnect between preclinical and humans' targets, which should assist in developing nonaddictive analgesics.

America's Opioid Epidemic: Supply and Demand Considerations

America is in the midst of an opioid epidemic characterized by aggressive prescribing practices, highly prevalent opioid misuse, and rising rates of prescription and illicit opioid overdose-related deaths. Medical and lay public sentiment have become more cautious with respect to prescription opioid use in the past few years, but a comprehensive strategy to reduce our reliance on prescription opioids is lacking. Addressing this epidemic through reductions in unnecessary access to these drugs while implementing measures to reduce demand will be important components of any comprehensive solution. Key supply-side measures include avoiding overprescribing, reducing diversion, and discouraging misuse through changes in drug formulations. Important demand-side measures center around educating patients and clinicians regarding the pitfalls of opioid overuse and methods to avoid unnecessary exposure to these drugs. Anesthesiologists, by virtue of their expertise in the use of these drugs and their position in guiding opioid use around the time of surgery, have important roles to play in reducing patient exposure to opioids and providing education about appropriate use. Aside from the many immediate steps that can be taken, clinical and basic research directed at understanding the interaction between pain and opioid misuse is critical to identifying the optimal use of these powerful pain relievers in clinical practice.

Breaking barriers to novel analgesic drug development

Acute and chronic pain complaints, although common, are generally poorly served by existing therapies. This unmet clinical need reflects a failure to develop novel classes of analgesics with superior efficacy, diminished adverse effects and a lower abuse liability than those currently available. Reasons for this include the heterogeneity of clinical pain conditions, the complexity and diversity of underlying pathophysiological mechanisms, and the unreliability of some preclinical pain models. However, recent advances in our understanding of the neurobiology of pain are beginning to offer opportunities for developing novel therapeutic strategies and revisiting existing targets, including modulating ion channels, enzymes and G-protein-coupled receptors.