As the nontherapeutic use of prescription medications escalates, serious associated consequences have also increased. This makes it essential to estimate misuse, abuse, and related events (MAREs) in ...the development and postmarketing adverse event surveillance and monitoring of prescription drugs accurately. However, classifications and definitions to describe prescription drug MAREs differ depending on the purpose of the classification system, may apply to single events or ongoing patterns of inappropriate use, and are not standardized or systematically employed, thereby complicating the ability to assess MARE occurrence adequately. In a systematic review of existing prescription drug MARE terminology and definitions from consensus efforts, review articles, and major institutions and agencies, MARE terms were often defined inconsistently or idiosyncratically, or had definitions that overlapped with other MARE terms. The Analgesic, Anesthetic, and Addiction Clinical Trials, Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership convened an expert panel to develop mutually exclusive and exhaustive consensus classifications and definitions of MAREs occurring in clinical trials of analgesic medications to increase accuracy and consistency in characterizing their occurrence and prevalence in clinical trials. The proposed ACTTION classifications and definitions are designed as a first step in a system to adjudicate MAREs that occur in analgesic clinical trials and postmarketing adverse event surveillance and monitoring, which can be used in conjunction with other methods of assessing a treatment's abuse potential.
There is tremendous interpatient variability in the response to analgesic therapy (even for efficacious treatments), which can be the source of great frustration in clinical practice. This has led to ...calls for "precision medicine" or personalized pain therapeutics (ie, empirically based algorithms that determine the optimal treatments, or treatment combinations, for individual patients) that would presumably improve both the clinical care of patients with pain and the success rates for putative analgesic drugs in phase 2 and 3 clinical trials. However, before implementing this approach, the characteristics of individual patients or subgroups of patients that increase or decrease the response to a specific treatment need to be identified. The challenge is to identify the measurable phenotypic characteristics of patients that are most predictive of individual variation in analgesic treatment outcomes, and the measurement tools that are best suited to evaluate these characteristics. In this article, we present evidence on the most promising of these phenotypic characteristics for use in future research, including psychosocial factors, symptom characteristics, sleep patterns, responses to noxious stimulation, endogenous pain-modulatory processes, and response to pharmacologic challenge. We provide evidence-based recommendations for core phenotyping domains and recommend measures of each domain.
Although pain reduction is commonly the primary outcome in chronic pain clinical trials, physical functioning is also important. A challenge in designing chronic pain trials to determine efficacy and ...effectiveness of therapies is obtaining appropriate information about the impact of an intervention on physical function. The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) and Outcome Measures in Rheumatology (OMERACT) convened a meeting to consider assessment of physical functioning and participation in research on chronic pain. The primary purpose of this article is to synthesize evidence on the scope of physical functioning to inform work on refining physical function outcome measurement. We address issues in assessing this broad construct and provide examples of frequently used measures of relevant concepts. Investigators can assess physical functioning using patient-reported outcome (PRO), performance-based, and objective measures of activity. This article aims to provide support for the use of these measures, covering broad aspects of functioning, including work participation, social participation, and caregiver burden, which researchers should consider when designing chronic pain clinical trials. Investigators should consider the inclusion of both PROs and performance-based measures as they provide different but also important complementary information. The development and use of reliable and valid PROs and performance-based measures of physical functioning may expedite development of treatments, and standardization of these measures has the potential to facilitate comparison across studies. We provide recommendations regarding important domains to stimulate research to develop tools that are more robust, address consistency and standardization, and engage patients early in tool development.
Interpreting randomized clinical trials (RCTs) is crucial to making decisions regarding the use of analgesic treatments in clinical practice. In this article, we report on an Initiative on Methods, ...Measurement, and Pain Assessment in Clinical Trials (IMMPACT) consensus meeting organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks, the purpose of which was to recommend approaches that facilitate interpretation of analgesic RCTs. We review issues to consider when drawing conclusions from RCTs, as well as common methods for reporting RCT results and the limitations of each method. These issues include the type of trial, study design, statistical analysis methods, magnitude of the estimated beneficial and harmful effects and associated precision, availability of alternative treatments and their benefit-risk profile, clinical importance of the change from baseline both within and between groups, presentation of the outcome data, and the limitations of the approaches used.
Valid and reliable biomarkers can play an important role in clinical trials as indicators of biological or pathogenic processes or as a signal of treatment response. Currently, there are no ...biomarkers for pain qualified by the U.S. Food and Drug Administration or the European Medicines Agency for use in clinical trials. This article summarizes an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials meeting in which 3 potential biomarkers were discussed for use in the development of analgesic treatments: 1) sensory testing, 2) skin punch biopsy, and 3) brain imaging. The empirical evidence supporting the use of these tests is described within the context of the 4 categories of biomarkers: 1) diagnostic, 2) prognostic, 3) predictive, and 4) pharmacodynamic. Although sensory testing, skin punch biopsy, and brain imaging are promising tools for pain in clinical trials, additional evidence is needed to further support and standardize these tests for use as biomarkers in pain clinical trials.
The applicability of sensory testing, skin biopsy, and brain imaging as diagnostic, prognostic, predictive, and pharmacodynamic biomarkers for use in analgesic treatment trials is considered. Evidence in support of their use and outlining problems is presented, as well as a call for further standardization and demonstrations of validity and reliability.
A number of pharmacologic treatments examined in recent randomized clinical trials (RCTs) have failed to show statistically significant superiority to placebo in conditions in which their efficacy ...had previously been demonstrated. Assuming the validity of previous evidence of efficacy and the comparability of the patients and outcome measures in these studies, such results may be a consequence of limitations in the ability of these RCTs to demonstrate the benefits of efficacious analgesic treatments vs placebo ("assay sensitivity"). Efforts to improve the assay sensitivity of analgesic trials could reduce the rate of falsely negative trials of efficacious medications and improve the efficiency of analgesic drug development. Therefore, an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting was convened in which the assay sensitivity of chronic pain trials was reviewed and discussed. On the basis of this meeting and subsequent discussions, the authors recommend consideration of a number of patient, study design, study site, and outcome measurement factors that have the potential to affect the assay sensitivity of RCTs of chronic pain treatments. Increased attention to and research on methodological aspects of clinical trials and their relationships with assay sensitivity have the potential to provide the foundation for an evidence-based approach to the design of analgesic clinical trials and expedite the identification of analgesic treatments with improved efficacy and safety.
Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of ...preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.
Opioid analgesics are commonly used for the treatment of chronic low back pain (CLBP); however, abuse potential is a major concern. This study used a randomized, double-blind, placebo-controlled, ...enriched-enrollment randomized-withdrawal study design to evaluate the safety, tolerability, and analgesic efficacy of an abuse-deterrent formulation of extended-release oxycodone, Xtampza ER, in opioid-naive and opioid-experienced adults with moderate-to-severe CLBP. Patients entered an open-label titration phase (N = 740); those who were successfully titrated on Xtampza ER (≥40 to ≤160 mg oxycodone hydrochloride equivalent per day) were randomized to active drug (N = 193) or placebo (N = 196) for 12 weeks. Primary efficacy results showed a statistically significant difference in average pain intensity from randomization baseline to treatment week 12 between the Xtampza ER and placebo groups (mean ±SE, -1.56 0.267; P < 0.0001). All sensitivity analyses results supported the primary result of the study. Secondary efficacy outcomes indicated that Xtampza ER vs placebo had more patients with improvement in patient global impression of change (26.4% vs 14.3%; P < 0.0001), longer time-to-exit from the study (58 vs 35 days; P = 0.0102), and a greater proportion of patients with ≥30% (49.2% vs 33.2%; P = 0.0013) and ≥50% (38.3% vs 24.5%; P = 0.0032) improvement in pain intensity. There was less rescue medication (acetaminophen) use in the Xtampza ER treatment group than in the placebo group. Xtampza ER had an adverse event profile consistent with other opioids and was well tolerated; no new safety concerns were identified. In conclusion, Xtampza ER resulted in clinically and statistically significant efficacy in patients with CLBP.
Trial Design
This was a phase III, randomized withdrawal, double-blind, placebo-controlled, enriched enrollment, parallel-group, multicenter study intended to demonstrate the safety, tolerability, ...and analgesic efficacy of oxycodone DETERx
®
(Xtampza™ ER) compared with matching placebo.
Methods
This post hoc analysis was performed using data from a subpopulation of enrolled patients who were ≥65 years of age. The study enrolled male and female patients with a clinical diagnosis of moderate-to-severe chronic low back pain for a minimum of 6 months prior to screening who required around-the-clock opioid therapy. To be eligible for enrollment, patients were required to have an average 24-h pain intensity score of ≥5 and ≤9 on an 11-point (0–10) Pain Intensity—Numerical Rating Scale at the screening visit. The study enrolled both opioid-experienced and opioid-naïve patients. The study consisted of an open-label titration phase followed by a 12-week double-blind maintenance phase. The dose range was 40–160 mg oxycodone hydrochloride equivalent per day. This post hoc analysis evaluated the safety, tolerability, and effectiveness of oxycodone DETERx among patients ≥65 years of age. The effectiveness of oxycodone DETERx was evaluated based on average pain intensity scores, Patient Global Impression of Change, responder analysis, and Kaplan–Meier survival analysis. The safety and tolerability of oxycodone DETERx were also evaluated. Patients were randomized to either oxycodone DETERx or placebo using a blocked randomization scheme in a 1:1 ratio. Randomization was stratified by previous opioid use (naïve or experienced). The study drug was coded in a manner that maintained the blinding. Study personnel and patients remained blinded to the assigned treatments throughout the study.
Results
For this post-hoc analysis, the intent-to-treat and randomized safety populations included 52 patients ≥65 years old, 26 each in the oxycodone DETERx and placebo groups, who participated in the study during the titration phase and were randomized to the double-blind maintenance phase. Clinically important pain reduction from screening was achieved with oxycodone DETERx, with the median pain intensity score decreasing from 7.50 at screening to 2.69 at Week 12. A clinically meaningful treatment difference of −0.9 in pain score between oxycodone DETERx and placebo was observed. All 18 elderly patients who completed the study reported improvement in pain, with 62% showing ≥30% improvement and 54% showing ≥50% improvement in pain intensity compared with patients on placebo (
p
= 0.0128 and
p
= 0.0501, respectively). Patients on oxycodone DETERx remained in the study longer than those on placebo. Of the 26 patients ≥65 years old randomized to continue oxycodone DETERx during the double-blind maintenance phase, 18 (69%) completed the study; only two patients (8%) in the oxycodone DETERx group discontinued due to adverse events. The safety and tolerability profiles showed no new or unexpected safety concerns. The adverse event profiles were similar between the titration and double-blind maintenance phases.
Conclusions
Oxycodone DETERx was efficacious and generally well tolerated in patients ≥65 years old.
Trial Registration
The study was registered with ClinicalTrials.gov (NCT01685684).
Oxycodone DETERx® (Collegium Pharmaceutical Inc, Canton, Massachusetts) is an extended‐release, microsphere‐in‐capsule, abuse‐deterrent formulation designed to retain its extended‐release properties ...after tampering (eg, chewing/crushing). This randomized, double‐blind, placebo‐controlled, triple‐dummy study evaluated the oral abuse potential of intact and chewed oxycodone DETERx capsules compared with crushed immediate‐release oxycodone. Subjects with a history of recreational opioid use who were nondependent/nontolerant to opioids were enrolled. Treatments included intact oxycodone DETERx (high‐fat, high‐calorie meal and fasted), chewed oxycodone DETERx (high‐fat, high‐calorie meal and fasted), crushed immediate‐release oxycodone (fasted), and placebo (high‐fat, high‐calorie meal). Plasma samples were collected to determine pharmacokinetic parameters. The primary endpoint was drug liking at the moment; other endpoints included drug effects questionnaire scores, Addiction Research Center Inventory/Morphine Benzedrine Group score, pupillometry measurements, and safety. Thirty‐eight subjects completed the study. Chewed and intact oxycodone DETERx were bioequivalent, unlike crushed immediate‐release oxycodone, which yielded higher peak oxycodone plasma concentrations compared with all methods of oxycodone DETERx administration. The mean maximum (peak) effect (Emax) for drug liking was significantly lower for chewed and intact oxycodone DETERx than for crushed immediate‐release oxycodone (P < .01). The time to Emax was significantly longer for chewed and intact oxycodone DETERx than for crushed immediate‐release oxycodone (P < .0001). Scores for feeling high and Addiction Research Center Inventory/Morphine Benzedrine Group scores demonstrated lower abuse potential for chewed and intact oxycodone DETERx compared with crushed immediate‐release oxycodone. Study treatments were well tolerated; no subjects experienced serious adverse events. These results demonstrate the lower oral abuse potential of chewed and intact oxycodone DETERx than crushed immediate‐release oxycodone.
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