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Supplemental Digital Content is Available in the Text., 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.

This article summarizes the results of a meeting convened by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) on key considerations and best practices governing the design of acute pain clinical trials. We discuss the role of early phase clinical trials, including pharmacokinetic-pharmacodynamic (PK-PD) trials, and the value of including both placebo and active standards of comparison in acute pain trials. This article focuses on single-dose and short-duration trials with emphasis on the perioperative and study design factors that influence assay sensitivity. Recommendations are presented on assessment measures, study designs, and operational factors. Although most of the methodological advances have come from studies of postoperative pain after dental impaction, bunionectomy, and other surgeries, the design considerations discussed are applicable to many other acute pain studies conducted in different settings.

Assessing and mitigating the abuse liability (AL) of analgesics is an urgent clinical and societal problem. Analgesics have traditionally been assessed in randomized clinical trials (RCTs) designed to demonstrate analgesic efficacy relative to placebo or an active comparator. In these trials, rigorous, prospectively designed assessment for AL is generally not performed. The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) convened a consensus meeting to review the available evidence and discuss methods for improving the assessment of the AL of analgesics in clinical trials in patients with pain. Recommendations for improved assessment include: (1) performing trials that include individuals with diverse risks of abuse; (2) improving the assessment of AL in clinical trials (eg, training study personnel in the principles of abuse and addiction behaviors, designing the trial to assess AL outcomes as primary or secondary outcome measures depending on the trial objectives); (3) performing standardized assessment of outcomes, including targeted observations by study personnel and using structured adverse events query forms that ask all subjects specifically for certain symptoms (such as euphoria and craving); and (4) collecting detailed information about events of potential concern (eg, unexpected urine drug testing results, loss of study medication, and dropping out of the trial). The authors also propose a research agenda for improving the assessment of AL in future trials.

Painful diabetic peripheral neuropathy (DPN) may not be adequately managed with available therapeutic options. This phase III, randomized-withdrawal, placebo-controlled trial evaluated the safety and efficacy of tapentadol extended release (ER) for relieving painful DPN.Patients (n = 588) with at least a 3-month history of opioid and/or non-opioid analgesic use for DPN, dissatisfaction with current treatment, and an average pain intensity score of at least 5 on an 11-point numerical rating scale (NRS; 0 = 'no pain,' 10 = 'pain as bad as you can imagine') were titrated to an optimal dose of tapentadol ER (100-250 mg bid) during a 3-week open-label phase. Subsequently, patients (n = 395) with at least a 1-point reduction in pain intensity were randomized 1:1 to receive placebo or the optimal fixed dose of tapentadol ER determined during the open-label phase for a 12-week double-blind phase.NCT00455520.The primary efficacy outcome was the change in average pain intensity from randomization, determined by twice-daily NRS measurements. Safety was assessed throughout the study.The least-squares mean difference between groups in the change in average pain intensity from the start of double-blind treatment to week 12 was -1.3 (95% confidence interval, -1.70 to -0.92; p 0.001, tapentadol ER vs. placebo). A total of 60.5% (356/588) of patients reported at least a 30% improvement in pain intensity from the start to the end of the open-label titration phase; of the patients who were randomized to tapentadol ER, 53.6% (105/196) reported at least a 30% improvement from pre-titration to week 12 of the double-blind phase. The most common treatment-emergent adverse events that occurred during double-blind treatment with tapentadol ER included nausea, anxiety, diarrhea, and dizziness. Potential limitations of this study are related to the enriched enrollment randomized-withdrawal trial design, which may result in a more homogeneous patient population during double-blind treatment and may present a risk of unblinding because of changes in side effects from the open-label to the double-blind phase.Compared with placebo, tapentadol ER 100-250 mg bid provided a statistically significant difference in the maintenance of a clinically important improvement in pain 1 , 2 and was well-tolerated by patients with painful DPN.

Background: Tapentadol is a novel, centrally acting analgesic with 2 mechanisms of action: µ-opioid receptor agonism and norepinephrine reuptake inhibition. This randomized, open-label phase 3 study (ClinicalTrials.gov Identifier: NCT00361504) assessed the long-term safety and tolerability of tapentadol extended release (ER) in patients with chronic knee or hip osteoarthritis pain or low back pain. Methods: Patients were randomized 4:1 to receive controlled, adjustable, oral, twice-daily doses of tapentadol ER (100 to 250 mg) or oxycodone HCl controlled release (CR; 20 to 50 mg) for up to 1 year. Efficacy evaluations included assessments at each study visit of average pain intensity (11-point numerical rating scale) over the preceding 24 hours. Treatment-emergent adverse events (TEAEs) and discontinuations were monitored throughout the study. Results: A total of 1,117 patients received at least 1 dose of study drug. Mean (standard error) pain intensity scores in the tapentadol ER and oxycodone CR groups, respectively, were 7.6 (0.05) and 7.6 (0.11) at baseline and decreased to 4.4 (0.09) and 4.5 (0.17) at endpoint. The overall incidence of TEAEs was 85.7% in the tapentadol ER group and 90.6% in the oxycodone CR group. In the tapentadol ER and oxycodone CR groups, respectively, TEAEs led to discontinuation in 22.1% and 36.8% of patients; gastrointestinal TEAEs led to discontinuation in 8.6% and 21.5% of patients. Conclusion: Tapentadol ER (100 to 250 mg bid) was associated with better gastrointestinal tolerability than oxycodone HCl CR (20 to 50 mg bid) and provided sustainable relief of moderate to severe chronic knee or hip osteoarthritis or low back pain for up to 1 year.

Background: Tapentadol is a novel, centrally acting analgesic with μ-opioid receptor agonist and norepinephrine reuptake inhibitor activity. Objective: To evaluate the efficacy and safety of tapentadol extended release (ER) compared with oxycodone controlled release (CR) for management of moderate to severe chronic osteoarthritis-related knee pain. Methods: This was a randomized, double-blind, active- and placebo-controlled, parallel-arm, multicentre, phase III study during which patients received tapentadol ER, oxycodone CR or placebo for a 3-week titration period followed by a 12-week maintenance period. The study was carried out at sites in Australia, Canada, New Zealand and the US. A total of 1030 patients with chronic osteoarthritis-related knee pain were randomized to receive tapentadol ER 100–250 mg twice daily, oxycodone HCl CR 20–50 mg twice daily or placebo. Primary endpoints (as determined prior to initiation of the study) were the changes from baseline in average daily pain intensity (rated by patients on an 11-point numerical rating scale) over the last week of maintenance and over the entire 12-week maintenance period; last observation carried forward was used to impute missing values after early treatment discontinuation. Results: Efficacy and safety were evaluated for 1023 patients. Tapentadol ER significantly reduced average pain intensity from baseline to week 12 of the maintenance period versus placebo (least squares mean [LSM] difference [95% CI], −0.7 [−1.04, −0.33]), and throughout the maintenance period (−0.7 [−1.00, −0.33]). Oxycodone CR significantly reduced average pain intensity from baseline throughout the maintenance period versus placebo (LSM difference [95% CI], −0.3 [−0.67, −0.00]) but not at week 12 (−0.3 [−0.68, 0.02]). A significantly higher percentage of patients achieved ≥50% improvement in pain intensity in the tapentadol ER group (32.0% [110/344]) compared with the placebo group (24.3% [82/337]; p = 0.027), indicating a clinically significant improvement in pain intensity, while a significantly lower percentage of patients achieved ≥50% improvement in pain intensity in the oxycodone CR group (17.3% [59/342]; p = 0.023 vs placebo). In the placebo, tapentadol ER and oxycodone CR groups, respectively, 61.1% (206/337), 75.9% (261/344) and 87.4% (299/342) of patients reported at least one treatment-emergent adverse event (TEAE); incidences of gastrointestinal-related TEAEs were 26.1% (88/337), 43.0% (148/344) and 67.3% (230/342). Conclusion: Treatment with tapentadol ER 100–250 mg twice daily or oxycodone HCl CR 20–50 mg twice daily was effective for the management of moderate to severe chronic osteoarthritis-related knee pain, with substantially lower incidences of gastrointestinal-related TEAEs associated with treatment with tapentadol ER than with oxycodone CR. [Trial registration number: NCT00421928 (ClinicalTrials.gov Identifier)]

There has been an increase in the number of chronic pain clinical trials in which the treatments being evaluated did not differ significantly from placebo in the primary efficacy analyses despite previous research suggesting that efficacy could be expected. These findings could reflect a true lack of efficacy or methodological and other aspects of these trials that compromise the demonstration of efficacy. There is substantial variability among chronic pain clinical trials with respect to important research design considerations, and identifying and addressing any methodological weaknesses would enhance the likelihood of demonstrating the analgesic effects of new interventions. An IMMPACT consensus meeting was therefore convened to identify the critical research design considerations for confirmatory chronic pain trials and to make recommendations for their conduct. We present recommendations for the major components of confirmatory chronic pain clinical trials, including participant selection, trial phases and duration, treatment groups and dosing regimens, and types of trials. Increased attention to and research on the methodological aspects of confirmatory chronic pain clinical trials has the potential to enhance their assay sensitivity and ultimately provide more meaningful evaluations of treatments for chronic pain.

Background: Tapentadol, a novel, centrally acting analgesic with 2 mechanisms of action (µopioid receptor agonism and norepinephrine reuptake inhibition), has been developed in an immediate-release (IR) and an extended-release (ER) formulation. Determination of the safety and equianalgesic ratios for conversion between formulations is important for physicians with patients taking tapentadol IR who may want to switch to tapentadol ER, or vice versa, for any reason. Objectives: To test whether the total daily dose (TDD) of tapentadol IR may be directly converted into a comparable TDD of tapentadol ER, and vice versa, with equivalent efficacy and comparable safety. Study Design: Randomized, double-blind, 2-period (2 weeks each) crossover study. Setting: Study centers (N = 13) in the United States. Methods: Patients with moderate to severe chronic low back pain received tapentadol IR 50, 75, or 100 mg every 4 or 6 hours (maximum TDD, 500 mg) during the 3-week open-label period to identify an optimal, stable dose of tapentadol IR for each patient. Patients were then randomized in a 1:1 ratio to receive, during the first 2-week double-blind period, either the optimal dose of tapentadol IR identified during the open-label period or a TDD of tapentadol ER (100, 150, 200, or 250 mg bid) that was as close as possible to the TDD of tapentadol IR from the open-label period. During a subsequent, 2-week double-blind period, patients received whichever formulation was not received during the first double-blind period. The primary endpoint was the mean average daily pain intensity (on an 11-point numerical rating scale) during the last 3 days of each double-blind treatment period. If the 95% confidence intervals (CIs) of the least squares mean difference between formulations were within the range of −2 to 2, the formulations were considered equivalent. Results: Of the 88 patients who were randomized, 72 completed both double-blind treatments, and 60 were included in the per-protocol analysis. The mean (standard deviation [SD]) pain intensity score decreased from 7.3 (1.19) pre-treatment to 4.2 (2.13) after 3 weeks of open-label treatment with tapentadol IR and remained constant throughout double-blind treatment (3.9 or 4.0 each week) for both formulations. The mean (SD) of the average pain intensity scores over the last 3 days of double-blind treatment was 3.9 (2.17) with tapentadol IR and 4.0 (2.29) with tapentadol ER, for an estimated difference of 0.1 (95% CI, −0.09 to 0.28). For both tapentadol IR and tapentadol ER, the median TDD administered was 300.0 mg, and acetaminophen was used by 39.5% and 45.2% of patients, respectively. The incidence of treatment-emergent adverse events during double-blind treatment was similar between the tapentadol IR and tapentadol ER groups. Limitations: Use of rescue medication theoretically could have influenced pain measurements, but in practice, pain measurements did not differ between treatments. Conclusions: Approximately equivalent TDDs of tapentadol IR and tapentadol ER provided equivalent analgesic efficacy for the relief of moderate to severe chronic low back pain and were similarly well tolerated, allowing for direct conversion between the 2 formulations. Key words: Chronic low back pain, conversion, efficacy, equivalence, extended release, immediate release, opioid, safety, tapentadol

To evaluate the relative efficacy and tolerability of tapentadol immediate release (IR) and oxycodone IR for management of moderate to severe pain following orthopedic surgery (bunionectomy).Randomized patients (N = 901) received oral tapentadol IR 50 or 75 mg, oxycodone HCl IR 10 mg, or placebo every 4-6 h over a 72-h period following surgery. Acetaminophen (or =2 g) was allowed in the first 12 h after the first dose of study drug. In the primary analysis, tapentadol IR (50 and 75 mg) was evaluated for efficacy superior to placebo and non-inferior to oxycodone HCl IR 10 mg (using sum of pain intensity difference [SPID] over 48 h), and tolerability superior to oxycodone IR (using incidence of treatment-emergent adverse events [TEAEs] of nausea and/or vomiting).Statistically significantly higher mean SPID(48) values were observed with tapentadol IR (50 and 75 mg) and oxycodone HCl IR 10 mg than placebo (all p0.001). The efficacy of tapentadol IR 50 mg and 75 mg was non-inferior to oxycodone HCl IR 10 mg. The incidence of TEAEs of nausea and/or vomiting was statistically significantly lower with tapentadol IR 50 mg versus oxycodone IR 10 mg (35 vs. 59%; p0.001). No statistically significant difference in the incidence of nausea and/or vomiting was observed between tapentadol IR 75 mg and oxycodone IR 10 mg (51 vs. 59%; p = 0.057). A possible limitation of this study was that the intense dose and patient monitoring may not represent real-world situations and may result in higher incidences of TEAEs than expected in a practice setting; this bias would be similar for all treatment groups.Clinically meaningful and statistically significant improvements were observed with tapentadol IR 50 mg and 75 mg compared with placebo for the relief of moderate-to-severe acute pain after orthopedic surgery. Tapentadol IR 50 mg and 75 mg were non-inferior to oxycodone HCl IR 10 mg for the treatment of acute pain based on the primary efficacy endpoint of SPID(48) and the pre-specified margin of 48 points. The incidence of nausea and/or vomiting was statistically significantly lower for tapentadol IR 50 mg and numerically lower for tapentadol IR 75 mg than for oxycodone HCl IR 10 mg.

a University of Washington, Seattle, WA 98195, USA b University of Rochester School of Medicine and Dentistry, Rochester, NY, USA c United States Food and Drug Administration, Rockville, MD, USA d Northwestern University, Chicago, IL, USA e Johnson and Johnson, Raritan, NY, USA f AstraZeneca, Wilmington, DE, USA g University of California San Diego, La Jolla, CA, USA h Merck and Company, Blue Bell, PA, USA i University of Texas, M.D. Anderson Cancer Center, USA j American Chronic Pain Association, Rocklin, CA, USA k Allergan, Inc, Irvine, CA, USA l National Institute of Dental and Craniofacial Research, Bethesda, MD, USA m University of Pennsylvania, Philadelphia, PA, USA n Johns Hopkins University, Baltimore, MD, USA o University Health Network and University of Toronto, Toronto, Canada p Novartis Pharmaceuticals, East Hanover, NJ, USA q VA Connecticut Healthcare System, West Haven, CT, USA r Yale University, New Haven, CT, USA s Celgene Corporation, Warren, NJ, USA t Pfizer Global Research and Development, Ann Arbor, MI, USA u Dalhousie University, Halifax, Nova Scotia, Canada v London Regional Cancer Centre, London, Ont., Canada

Proof-of-concept (POC) clinical trials play an important role in developing novel treatments and determining whether existing treatments may be efficacious in broader populations of patients. The goal of most POC trials is to determine whether a treatment is likely to be efficacious for a given indication and thus whether it is worth investing the financial resources and participant exposure necessary for a confirmatory trial of that intervention. A challenge in designing POC trials is obtaining sufficient information to make this important go/no-go decision in a cost-effective manner. An IMMPACT consensus meeting was convened to discuss design considerations for POC trials in analgesia, with a focus on maximizing power with limited resources and participants. We present general design aspects to consider including patient population, active comparators and placebos, study power, pharmacokinetic–pharmacodynamic relationships, and minimization of missing data. Efficiency of single-dose studies for treatments with rapid onset is discussed. The trade-off between parallel-group and crossover designs with respect to overall sample sizes, trial duration, and applicability is summarized. The advantages and disadvantages of more recent trial designs, including N-of-1 designs, enriched designs, adaptive designs, and sequential parallel comparison designs, are summarized, and recommendations for consideration are provided. More attention to identifying efficient yet powerful designs for POC clinical trials of chronic pain treatments may increase the percentage of truly efficacious pain treatments that are advanced to confirmatory trials while decreasing the percentage of ineffective treatments that continue to be evaluated rather than abandoned.

Background: Tapentadol has demonstrated analgesic efficacy across a range of pain conditions. Objective: In a head-to-head study of up to 10 days in duration, the analgesic efficacy and tolerability of tapentadol immediate release (IR) versus oxycodone IR using a flexible dosing regimen were compared in patients with acute low back pain (LBP) and associated radicular leg pain. Study Design: Randomized (1:1), double-blind, parallel-group study (NCT00986180). Independent Ethics Committee/Institutional Review Board approval of the protocol was obtained. Setting: Ninety US outpatient treatment centers. Methods: Patients with moderate to severe, acute LBP received tapentadol IR (50, 75, or 100 mg) or oxycodone HCl IR (5, 10, or 15 mg) every 4 to 6 hours as needed for pain for up to 10 days. Patients reported current pain intensity twice daily (11-point numerical rating scale). The primary efficacy endpoint was the sum of pain intensity differences (SPID) over 120 hours for LBP. Tapentadol IR was considered non-inferior to oxycodone IR if the upper bound of the 95% confidence interval (CI) for the least-squares mean (LSM) difference in SPID120 was less than 120. Secondary efficacy endpoints included 2-, 3-, and 10-day SPID for LBP; 2-, 3-, 5-, and 10-day SPID for index leg pain; 30% and 50% responder rates; patient and clinician global impressions of change; and patient satisfaction. Results: The safety population included 645 patients, and the modified intent-to-treat population included 585 patients. In the tapentadol IR and oxycodone IR groups, respectively, 86.3% (277/321) and 82.7% (268/324) of patients completed the study. The most common reason for study withdrawal in both treatment groups was adverse events (tapentadol IR, 6.5% [21/321]; oxycodone IR, 7.1% [23/324]). The LSM (standard error) SPID120 for LBP was 264.6 (11.43) for tapentadol IR (n = 287) and 264.0 (11.22) for oxycodone IR (n = 298). The 95% CI for the LSM difference was −32.1 to 30.9; therefore, tapentadol IR was non-inferior to oxycodone IR for relief of LBP. No significant differences were observed between tapentadol IR and oxycodone IR for other SPID endpoints or for responder rates. At the end of the study, in the tapentadol IR and oxycodone IR treatment groups, respectively, approximately two-thirds of patients (66.2% vs 66.2%) and clinicians (67.9% vs 66.6%) rated patients’ overall condition as “very much improved” or “much improved,” and more than 75% of patients (79.3% vs 78.9%) were “very satisfied” or “somewhat satisfied” with their treatment. In the tapentadol IR and oxycodone IR groups, respectively, 52.3% (168/321) and 58.0% (188/324) of patients reported at least one treatment-emergent adverse event (TEAE); the most common (≥ 10%) TEAEs were vomiting (15.9% vs 24.7%), nausea (15.9% vs 20.7%), and dizziness (11.8% vs 10.5%). Vomiting (odds ratio [95% CI], 1.74 [1.17 - 2.57]) and constipation (3.43 [1.45 - 8.11]) were significantly more likely to occur in the oxycodone IR treatment group. Two (0.6%) patients in the tapentadol IR group and 3 (0.9%) patients in the oxycodone IR group experienced treatment-emergent serious adverse events. Limitations: Strict patient monitoring is generally not representative of real-world medical practice; consequently, higher incidences of TEAEs may have been reported than would be expected in a typical practice setting; it is anticipated that this bias would be similar for both treatment groups. Conclusions: This head-to-head study demonstrated that tapentadol IR had comparable analgesic efficacy and overall safety to that of oxycodone IR for the relief of moderate to severe, acute LBP and associated radicular leg pain when using flexible dosing regimens that reflect typical use in clinical practice; however, tapentadol IR demonstrated a better gastrointestinal tolerability profile, particularly for the common opioid-related TEAEs of vomiting and constipation. Clinical Trial Registration: NCT00986180 Key words: Tapentadol, oxycodone, acute low back pain, radicular leg pain, neuropathic pain, flexible dosing, radiculopathy, gastrointestinal tolerability

A critical component in development of opioid analgesics is assessment of their abuse liability (AL). Standardization of approaches and measures used in assessing AL have the potential to facilitate comparisons across studies, research laboratories, and drugs. The goal of this report is to provide consensus recommendations regarding core outcome measures for assessing the abuse potential of opioid medications in humans in a controlled laboratory setting. Although many of the recommended measures are appropriate for assessing the AL of medications from other drug classes, the focus here is on opioid medications because they present unique risks from both physiological (e.g., respiratory depression, physical dependence) and public health (e.g., individuals in pain) perspectives. A brief historical perspective on AL testing is provided, and those measures that can be considered primary and secondary outcomes and possible additional outcomes in AL assessment are then discussed. These outcome measures include the following: subjective effects (some of which comprise the primary outcome measures, including drug liking; physiological responses; drug self-administration behavior; and cognitive and psychomotor performance. Before presenting recommendations for standardized approaches and measures to be used in AL assessments, the appropriateness of using these measures in clinical trials with patients in pain is discussed.

Objective: To evaluate via retrospective analysis the efficacy and tolerability of tapentadol extended release (ER; 100-250 mg bid) based on patient-specific factors, including baseline pain intensity, prior opioid experience, gender, and body mass index (BMI). Design: Data were pooled from three randomized, double-blind phase III studies of similar design that evaluated the efficacy and tolerability of tapentadol ER for the management of moderate to severe, chronic osteoarthritis knee pain (NCT00421928, NCT00486811) or low back pain (NCT00449176). Setting: In the original trials, patients were recruited at primary, secondary, and tertiary care centers, institutional settings, and private practices in North America, Europe, Australia, and New Zealand. Patients: Data were analyzed separately for groups of patients divided by baseline pain intensity, prior opioid experience, gender, and BMI. Interventions: Patients received twice-daily placebo, tapentadol ER (100-250 mg), or oxycodone HCl controlled release (CR; 20-50 mg) for a 3-week titration and 12-week maintenance period. Main outcome measures: Changes from baseline in average pain intensity (11-point numerical rating scale) at week 12 of the maintenance period and for the overall maintenance period. Results: Efficacy and tolerability were evaluated in 2,968 and 2,974 patients, respectively. The efficacy of tapentadol ER was shown in subpopulations divided by baseline pain intensity, prior opioid experience, gender, and BMI. Tapentadol ER was also shown to be well tolerated and associated with better gastrointestinal tolerability than oxycodone CR in the evaluated subpopulations (divided by prior opioid experience and gender). Conclusions: Results suggest that tapentadol ER (100-250 mg bid) provides similar pain relief and tolerability, regardless of baseline pain intensity, prior opioid experience, gender, or BMI.

Opioids are essential to the management of pain in many patients, but they also are associated with potential risks for abuse, overdose, and diversion. A number of efforts have been devoted to the development of abuse-deterrent formulations of opioids to reduce these risks. This article summarizes a consensus meeting that was organized to propose recommendations for the types of clinical studies that can be used to assess the abuse deterrence of different opioid formulations. Due to the many types of individuals who may be exposed to opioids, an opioid formulation will need to be studied in several populations using various study designs in order to determine its abuse-deterrent capabilities. It is recommended that the research conducted to evaluate abuse deterrence should include studies assessing: (1) abuse liability; (2) the likelihood that opioid abusers will find methods to circumvent the deterrent properties of the formulation; (3) measures of misuse and abuse in randomized clinical trials involving pain patients with both low risk and high risk of abuse; and (4) post-marketing epidemiological studies.

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.

Two randomized, double-blind, placebo-controlled studies in acute and chronic pain treatment, powered to assess noninferiority of the efficacy of tapentadol immediate release (IR) (50 mg, 75 mg) versus oxycodone hydrochloride (HCl) IR (10 mg), established comparable efficacy of tapentadol IR with oxycodone HCl IR, and suggested tapentadol IR's improved gastrointestinal tolerability. The impact of these equianalgesic doses of tapentadol and oxycodone HCl on bowel function and gastrointestinal tolerability was then directly assessed in the current study, using a validated bowel function diary to comprehensively assess opioid-induced constipation symptoms and outcomes.In this double-blind study, patients with end-stage joint disease were randomized to tapentadol IR (50 mg or 75 mg), oxycodone HCl IR 10 mg, or placebo. Treatment with IR formulations (14 days) was followed by treatment (28 days) with extended-release (ER) formulations of active drugs (or placebo).Oxycodone HCl IR treatment significantly decreased (P0.001) mean (SD) number of spontaneous bowel movements over the 14-day period (average per week: [6.7 (5.44)] versus tapentadol IR 50 mg [9.0 (4.04)], tapentadol IR 75 mg [8.6 (4.65)], and placebo [9.9 (5.16)]) (primary measure), confirming the tolerability findings of the earlier studies. Additionally, incidences of nausea and vomiting were significantly lower over the 14-day period (nominal P0.001) for tapentadol IR 50 and 75 mg, versus oxycodone HCl IR 10 mg. Results with ER formulations of tapentadol and oxycodone HCl over a longer treatment period were consistent with those of IR formulations.Tapentadol IR (50 mg, 75 mg) consistently demonstrated superior gastrointestinal tolerability, including for the most commonly reported events, such as nausea, vomiting, and constipation at doses that provide comparable efficacy with oxycodone HCl IR 10 mg. These findings validate and extend the tolerability findings of the two earlier studies that established comparable efficacy of these tapentadol and oxycodone HCl doses.

Tapentadol is a novel, centrally acting analgesic with 2 mechanisms of action: µ-opioid receptor agonism and norepinephrine reuptake inhibition. This randomized, open-label phase 3 study (ClinicalTrials.gov Identifier: NCT00361504) assessed the long-term safety and tolerability of tapentadol extended release (ER) in patients with chronic knee or hip osteoarthritis pain or low back pain.Patients were randomized 4:1 to receive controlled, adjustable, oral, twice-daily doses of tapentadol ER (100 to 250 mg) or oxycodone HCl controlled release (CR; 20 to 50 mg) for up to 1 year. Efficacy evaluations included assessments at each study visit of average pain intensity (11-point numerical rating scale) over the preceding 24 hours. Treatment-emergent adverse events (TEAEs) and discontinuations were monitored throughout the study.A total of 1,117 patients received at least 1 dose of study drug. Mean (standard error) pain intensity scores in the tapentadol ER and oxycodone CR groups, respectively, were 7.6 (0.05) and 7.6 (0.11) at baseline and decreased to 4.4 (0.09) and 4.5 (0.17) at endpoint. The overall incidence of TEAEs was 85.7% in the tapentadol ER group and 90.6% in the oxycodone CR group. In the tapentadol ER and oxycodone CR groups, respectively, TEAEs led to discontinuation in 22.1% and 36.8% of patients; gastrointestinal TEAEs led to discontinuation in 8.6% and 21.5% of patients.Tapentadol ER (100 to 250 mg bid) was associated with better gastrointestinal tolerability than oxycodone HCl CR (20 to 50 mg bid) and provided sustainable relief of moderate to severe chronic knee or hip osteoarthritis or low back pain for up to 1 year.

To evaluate the efficacy and safety of tapentadol extended release (ER) for the management of moderate to severe chronic low back pain.Patients (N = 981) were randomized 1:1:1 to receive tapentadol ER 100 - 250 mg b.i.d., oxycodone HCl controlled release (CR) 20 - 50 mg b.i.d., or placebo over 15 weeks (3-week titration period, 12-week maintenance period).Efficacy was assessed as change from baseline in average pain intensity (11-point NRS) at week 12 of the maintenance period and throughout the maintenance period; last observation carried forward was used to impute missing pain scores. Adverse events (AEs) were monitored throughout the study.Tapentadol ER significantly reduced average pain intensity versus placebo at week 12 (least squares mean difference vs placebo [95% confidence interval], -0.8 [-1.22, -0.47]; p0.001) and throughout the maintenance period (-0.7 [-1.06,-0.35]; p0.001). Oxycodone CR significantly reduced average pain intensity versus placebo at week 12 (-0.9 [-1.24,-0.49]; p0.001) and throughout the maintenance period (-0.8 [-1.16,-0.46]; p0.001). Tapentadol ER was associated with a lower incidence of treatment-emergent AEs (TEAEs) than oxycodone CR. Gastrointestinal TEAEs, including constipation, nausea, and vomiting, were among the most commonly reported TEAEs (placebo, 26.3%; tapentadol ER, 43.7%; oxycodone CR, 61.9%). The odds of experiencing constipation or the composite of nausea and/or vomiting were significantly lower with tapentadol ER than with oxycodone CR (both p0.001).Tapentadol ER (100 - 250 mg b.i.d.) effectively relieved moderate to severe chronic low back pain over 15 weeks and had better gastrointestinal tolerability than oxycodone HCl CR (20 - 50 mg b.i.d.).

Tapentadol, a novel, centrally acting analgesic with 2 mechanisms of action (mu-opioid receptor agonism and norepinephrine reuptake inhibition), has been developed in an immediate-release (IR) and an extended-release (ER) formulation. Determination of the safety and equianalgesic ratios for conversion between formulations is important for physicians with patients taking tapentadol IR who may want to switch to tapentadol ER, or vice versa, for any reason.To test whether the total daily dose (TDD) of tapentadol IR may be directly converted into a comparable TDD of tapentadol ER, and vice versa, with equivalent efficacy and comparable safety.Randomized, double-blind, 2-period (2 weeks each) crossover study.Study centers (N = 13) in the United States.Patients with moderate to severe chronic low back pain received tapentadol IR 50, 75, or 100 mg every 4 or 6 hours (maximum TDD, 500 mg) during the 3-week open-label period to identify an optimal, stable dose of tapentadol IR for each patient. Patients were then randomized in a 1:1 ratio to receive, during the first 2-week double-blind period, either the optimal dose of tapentadol IR identified during the open-label period or a TDD of tapentadol ER (100, 150, 200, or 250 mg bid) that was as close as possible to the TDD of tapentadol IR from the open-label period. During a subsequent, 2-week double-blind period, patients received whichever formulation was not received during the first double-blind period. The primary endpoint was the mean average daily pain intensity (on an 11-point numerical rating scale) during the last 3 days of each double-blind treatment period. If the 95% confidence intervals (CIs) of the least squares mean difference between formulations were within the range of -2 to 2, the formulations were considered equivalent.Of the 88 patients who were randomized, 72 completed both double-blind treatments, and 60 were included in the per-protocol analysis. The mean (standard deviation [SD]) pain intensity score decreased from 7.3 (1.19) pre-treatment to 4.2 (2.13) after 3 weeks of open-label treatment with tapentadol IR and remained constant throughout double-blind treatment (3.9 or 4.0 each week) for both formulations. The mean (SD) of the average pain intensity scores over the last 3 days of double-blind treatment was 3.9 (2.17) with tapentadol IR and 4.0 (2.29) with tapentadol ER, for an estimated difference of 0.1 (95% CI, -0.09 to 0.28). For both tapentadol IR and tapentadol ER, the median TDD administered was 300.0 mg, and acetaminophen was used by 39.5% and 45.2% of patients, respectively. The incidence of treatment-emergent adverse events during double-blind treatment was similar between the tapentadol IR and tapentadol ER groups.Use of rescue medication theoretically could have influenced pain measurements, but in practice, pain measurements did not differ between treatments.Approximately equivalent TDDs of tapentadol IR and tapentadol ER provided equivalent analgesic efficacy for the relief of moderate to severe chronic low back pain and were similarly well tolerated, allowing for direct conversion between the 2 formulations.NCT00594516.

An essential component of the interpretation of results of randomized clinical trials of treatments for chronic pain involves the determination of their clinical importance or meaningfulness. This involves two distinct processes--interpreting the clinical importance of individual patient improvements and the clinical importance of group differences--which are frequently misunderstood. In this article, we first describe the essential differences between the interpretation of the clinical importance of patient improvements and of group differences. We then discuss the factors to consider when evaluating the clinical importance of group differences, which include the results of responder analyses of the primary outcome measure, the treatment effect size compared to available therapies, analyses of secondary efficacy endpoints, the safety and tolerability of treatment, the rapidity of onset and durability of the treatment benefit, convenience, cost, limitations of existing treatments, and other factors. The clinical importance of individual patient improvements can be determined by assessing what patients themselves consider meaningful improvement using well-described methods. In contrast, the clinical meaningfulness of group differences must be determined by a multi-factorial evaluation of the benefits and risks of the treatment and of other available treatments for the condition in light of the primary goals of therapy. Such determinations must be conducted on a case-by-case basis, and are ideally informed by patients and their significant others, clinicians, researchers, statisticians, and representatives of society at large.

Tapentadol is a novel, centrally acting analgesic with two mechanisms of action, mu-opioid receptor agonism and norepinephrine reuptake inhibition, in a single molecule. This phase III, randomized, double-blind, active-controlled study evaluated the tolerability of tapentadol immediate release (IR) and oxycodone IR for low back pain or osteoarthritis pain (hip or knee), using flexible dosing over 90 days.Patients (N = 878) were randomly assigned (4:1 ratio) to receive tapentadol IR (50 or 100 mg, q4-6h, p.o.) or oxycodone IR (10 or 15 mg, q4-6h, p.o.). Tapentadol IR was evaluated for tolerability over 90 days, tolerability relative to oxycodone IR, withdrawal symptoms, and pain intensity. This study was not placebo-controlled, which limited efficacy evaluations.In total, 849 intent-to-treat patients received tapentadol IR (n = 679) or oxycodone IR (n = 170), and among these, 391 patients (57.6%) in the tapentadol IR group and 86 patients (50.6%) in the oxycodone IR group completed the study. Gastrointestinal events, including nausea (18.4% vs 29.4%), vomiting (16.9% vs 30.0%), and constipation (12.8% vs 27.1%), were reported by 44.2% of patients receiving tapentadol IR and 63.5% of patients receiving oxycodone IR, respectively. Nervous system events, including dizziness (18.1% vs 17.1%), headache (11.5% vs 10.0%), and somnolence (10.2% vs 9.4%), were reported by 36.7% of patients receiving tapentadol and 37.1% of patients receiving oxycodone, respectively. Odds ratios (tapentadol:oxycodone) showed that the incidences of somnolence and dizziness were similar; however, nausea, vomiting, and constipation were significantly less likely with tapentadol IR compared with oxycodone IR. The pattern of withdrawal symptoms suggests that drug tapering may not be necessary after tapentadol IR treatment of this duration. Pain intensity measurements showed similar efficacy for tapentadol and oxycodone.During this 90-day study, tapentadol IR was associated with improved gastrointestinal tolerability compared with oxycodone IR while providing similar pain relief. Trial registration information: NCT00364546.

A consensus meeting was convened by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) to provide recommendations for interpreting clinical importance of treatment outcomes in clinical trials of the efficacy and effectiveness of chronic pain treatments. A group of 40 participants from universities, governmental agencies, a patient self-help organization, and the pharmaceutical industry considered methodologic issues and research results relevant to determining the clinical importance of changes in the specific outcome measures previously recommended by IMMPACT for 4 core chronic pain outcome domains: (1) Pain intensity, assessed by a 0 to 10 numerical rating scale; (2) physical functioning, assessed by the Multidimensional Pain Inventory and Brief Pain Inventory interference scales; (3) emotional functioning, assessed by the Beck Depression Inventory and Profile of Mood States; and (4) participant ratings of overall improvement, assessed by the Patient Global Impression of Change scale. It is recommended that 2 or more different methods be used to evaluate the clinical importance of improvement or worsening for chronic pain clinical trial outcome measures. Provisional benchmarks for identifying clinically important changes in specific outcome measures that can be used for outcome studies of treatments for chronic pain are proposed. Perspective Systematically collecting and reporting the recommended information needed to evaluate the clinical importance of treatment outcomes of chronic pain clinical trials will allow additional validation of proposed benchmarks and provide more meaningful comparisons of chronic pain treatments.

193 (P>0.05) and -0.05±0.06 HbA1c (P>0.05). Significant differences were also seen between nuts and muffins with greater falls on nuts for LDL-C (-0.19±0.12 mmol/L, P=0.03). Nut intake directly related to change in LDL-C (r= -.24, n=98, P