Opioids for Osteoarthritis: Cross-Sectional Survey of Patient Perspectives and Satisfaction

Patients often take opioids to relieve osteoarthritis (OA) pain despite limited benefits and potential harms. This study aimed to compare cross-sectional perspectives of patients that were taking prescription opioid (N = 471) or nonopioid medications (N = 185) for OA in terms of satisfaction, expectations of effectiveness, and concerns. Patients prescribed opioids (>7 days) reported more prior treatments (2.47 vs. 1.74), greater mean pain intensity (5.47 vs. 4.11), and worse quality of life (EQ-5D-5L index value mean 0.45 vs. 0.71) than patients prescribed nonopioid medications (all p < 0.0001). Based on linear regression models adjusting for demographics and pain intensity, patients prescribed opioids were less satisfied with overall regimen (3.40 vs. 3.67, p = 0.0322), had less belief that medications were meeting effectiveness expectations (2.72 vs. 3.13, p < 0.0001), and had more concerns about treatments being "not very good" (3.66 vs. 3.22, p = 0.0026) and addiction (3.30 vs. 2.65, p < 0.0001) than patients prescribed nonopioid regimens. When the models were replicated for subgroups with ≥30 days' medication regimen duration, the findings were consistent with the main analyses. Patients have concerns about the risk of opioid addiction, but those with greater disease burden and more prior treatments continue taking opioid regimens.

Predicting Treatment Responses in Patients With Osteoarthritis: Results From Two Phase III Tanezumab Randomized Clinical Trials

Prediction of treatment responses is essential to move forward translational science. Our question was to identify patient-based variables that predicted responses to treatments. We conducted secondary analyses on pooled data from two randomized phase III clinical trials (NCT02697773 and NCT02709486) conducted in participants with moderate to severe osteoarthritis randomized to subcutaneous placebo (n = 514) or tanezumab 2.5 mg (n = 514). We used gradient boosted regression trees to identify variables that predicted Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain subscale scores at Week 16 and marginal plots to determine the directional relationship between each variable category and responses to placebo or tanezumab within the models. We also used Virtual Twins models to identify potential subgroups of response to the active treatment vs. placebo. We found that responses to placebo were predicted by baseline WOMAC Physical Function, baseline WOMAC Pain, the radiographic classification of the index joint, and the standard deviation of diary pain scores at baseline. In contrast, baseline WOMAC Pain along with failure of prior medications, duration of disease, and standard deviation of diary pain scores at baseline were predictive of tanezumab responses as expressed by the WOMAC Pain scores at Week 16. Those who responded to tanezumab vs. placebo were identified based on the radiographic classification of the index joint and either age or smoking status. These secondary-data analyses identified distinct and common patient-based variables to predict response to placebo or tanezumab. These findings will inform the design of future clinical trials, helping to move forward clinical pharmacology and translational science.

Opioid Prescribing for Osteoarthritis: Cross-Sectional Survey among Primary Care Physicians, Rheumatologists, and Orthopaedic Surgeons

Opioids are often prescribed for osteoarthritis (OA) pain, despite recommendations to limit use due to minimal benefits and associated harms. This study aimed to assess physicians' practice patterns and perceptions regarding opioids by specialty one year following the Centers for Disease Control and Prevention (CDC) published guidance on opioid prescribing. The 139/153 (90.8%) physicians who reported prescribing opioids in the previous year reported decreased prescribing for mild OA (51.3%, 26.5% and 33.3% of primary care physicians, rheumatologists, and orthopaedic surgeons, respectively), moderate OA (50.0%, 47.1% and 48.1%) and severe OA (43.6%, 41.2% and 44.4%). Prescribing changes were attributed to the CDC guidelines for 58.9% of primary care physicians, 59.1% of rheumatologists, and 73.3% of orthopaedic surgeons. Strong opioids were mostly reserved as third-line treatment. Although treatment effectiveness post-CDC guidelines was not assessed, perceptions of efficacy and quality of life with opioids significantly differed across specialties, whereas perceptions of safety, convenience/acceptability and costs did not. Physicians generally agreed on the barriers to opioid prescribing, with fear of addiction and drug abuse being the most important. Across specialties, physicians reported decreased opioid prescribing for OA, irrespective of OA severity, and in most cases attributed changes in prescribing to the CDC guideline.

Factors associated with physician-reported treatment status of patients with osteoarthritis pain

BACKGROUND

Osteoarthritis (OA) is typically associated with pain, but many patients are not treated.

METHODS

This point in time study explored factors associated with treatment status, using logistic regression of data from the Adelphi OA Disease Specific Programme conducted in the United States. Patients' treatment status was based on physician-reported, current: 1) prescription medication for OA vs. none; and 2) physician treatment (prescription medication and/or recommendation for specified nonpharmacologic treatment for OA [physical or occupational therapy, acupuncture, transcutaneous electrical nerve stimulation, or cognitive behavior therapy/psychotherapy]) vs. self-management (no prescription medication or specified nonpharmacologic treatment).

RESULTS

The 841 patients (including 57.0% knee OA, 31.9% hip OA) reported mild (45.4%) or moderate or severe (54.6%) average pain intensity over the last week. The majority were prescribed medication and/or recommended specified nonpharmacologic treatment; 218 were not prescription-medicated and 122 were self-managed. Bivariate analyses showed less severe patient-reported pain intensity and physician-rated OA severity, fewer joints affected by OA, lower proportion of joints affected by knee OA, better health status, lower body mass index, and lower ratings for cardiovascular and gastrointestinal risks, for those not prescribed medication (vs. prescription-medicated). Multivariate analyses confirmed factors significantly (p < 0.05) associated with prescription medication included (odds ratio): physician-rated current moderate OA severity (vs. mild, 2.03), patient-reported moderate OA severity 6 months ago (vs. mild, 1.71), knee OA (vs. not, 1.81), physician-recommended (0.28) and patient-reported (0.43) over-the-counter medication use (vs. not), prior surgery for OA (vs. not, 0.37); uncertain income was also significant. Factors significantly (p < 0.05) associated with physician treatment included (odds ratio): physician-recommended nonpharmacologic therapy requiring no/minimal medical supervision (vs. not, 2.21), physician-rated current moderate OA severity (vs. mild, 2.04), patient-reported over-the-counter medication use (vs. not, 0.26); uncertain time since diagnosis was also significant. Patient-reported pain intensity and most demographic factors were not significant in either model.

CONCLUSIONS

Approximately 1 in 4 patients were not prescribed medication and 1 in 7 were self-managed, although many were using over-the-counter medications or nonpharmacologic therapies requiring no/minimal medical supervision. Multiple factors were significantly associated with treatment status, including OA severity and over-the-counter medication, but not pain intensity or most demographics.

Gender, age, disease severity, body mass index and diabetes may not affect response to subcutaneous tanezumab in patients with osteoarthritis after 16 weeks of treatment. A subgroup analysis of placebo-controlled trials

AIM

To assess the impact of pre-specified patient characteristics on efficacy and safety of subcutaneous tanezumab in patients with osteoarthritis (OA).

METHODS

Data were pooled from two (efficacy; N = 1545) or three (safety; N = 1754) phase 3 placebo-controlled trials. Change from baseline to week 16 in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain, WOMAC Physical Function and patient global assessment of OA (PGA-OA) scores was compared between tanezumab (2.5 and 5 mg) and placebo groups via analysis of covariance. Treatment-emergent adverse events (TEAEs) were summarised descriptively. Analyses were done in patient subgroups (men or women; age <65, ≥65, or ≥75 years; body mass index [BMI] <25, 25 to <30, 30 to <35 or ≥35 kg/m² ; diabetes or no diabetes; baseline WOMAC Pain score <7 or ≥7; and Kellgren-Lawrence [KL] grades 2, 3 or 4 in the index joint) and the overall population.

RESULTS

In all subgroups, improvements in WOMAC Pain were numerically greater and often statistically significant (P < .05) for both tanezumab groups compared with placebo. Results were similar for WOMAC Physical Function and PGA-OA. TEAE profiles were generally consistent across subgroups and similar to the overall population (ie slightly higher rates of TEAEs, serious TEAEs and severe TEAEs with tanezumab relative to placebo) with a few exceptions. Exceptions included women reporting slightly more TEAEs with tanezumab than men, and patients with diabetes reporting slightly more severe TEAEs with tanezumab than patients without diabetes. Additionally, TEAEs were more frequent with tanezumab than placebo in the age ≥65 and ≥75 years, but not the age <65 years, subgroups.

CONCLUSIONS

Efficacy and safety/tolerability of tanezumab may not be meaningfully impacted by gender, age, BMI, diabetes status, baseline pain severity or KL grade in the index joint. Conclusions are limited by low patient number in some subgroups. Clinicaltrials.gov: NCT02697773, NCT02709486, NCT01089725.

Concern about addiction is associated with lower quality of life in patients with osteoarthritis: an exploratory, real-world data analysis

PURPOSE

To evaluate the relationship between self-reported concerns about becoming addicted to a medication and health-related quality of life (HRQoL) in patients with osteoarthritis (OA).

METHODS

This real-world study used patient-level cross-sectional survey data collected from the US Adelphi Disease Specific Programme (DSP). The DSP for OA selected 153 physicians who collected de-identified data on their next nine adult patients with OA. Each patient completed a disease-relevant survey, which included the Likert-scale question, "I am concerned about becoming addicted to my medicine," (CAA) with responses ranging from "completely disagree" [1] to "completely agree" [5]. HRQoL was measured by the EQ-5D-5L index value and the EQ Visual Analogue Scale (VAS). A set of ordinary least squares regressions using HRQoL measures as outcomes and CAA as a continuous predictor were estimated. Standardized effect size (ES) was used to gauge the magnitude of effects.

RESULTS

A total of 866 patients with OA completed the survey (female, 61.2%; White, 77.7%; mean age, 64.2 years). Of the 775 patients who completed the CAA question, almost one-third responded that they "agree" (18%) or "completely agree" (11%), while 27% responded "completely disagree" and 20% "disagree." Regression analyses found that patients who have concerns about medication addiction have significantly different EQ-5D-5L index values and EQ VAS scores compared with patients who do not have this concern (p < 0.0001).

CONCLUSION

Our findings suggest that concern about medication addiction in patients with OA may have an impact on patient HRQoL, with more concerned patients reporting poorer HRQoL outcomes.

Multimodal Treatment Patterns for Osteoarthritis and Their Relationship to Patient-Reported Pain Severity: A Cross-Sectional Survey in the United States

Purpose

The purpose of this study was to assess how patient-reported pain is related to osteoarthritis (OA) treatment patterns in routine clinical practice.

Patients and Methods

Data were collected between February and May 2017 from 153 United States (US) primary care physicians, rheumatologists, and orthopedic surgeons. Each invited up to nine consecutive patients to rate their OA pain in the last week. Physicians provided demographic, clinical, and treatment information for patients, including nonpharmacologic therapies ever recommended, currently recommended over-the-counter (OTC) medications, and currently and ever prescribed medications for the management of OA. Findings for patients with mild (0─3), moderate (4─6), and severe current pain (7─10) were compared using appropriate statistics.

Results

Among the 841 patients (61% female; mean 65 years; 57% knee OA), 45% reported mild, 36% moderate, and 19% severe current OA pain. Current treatment modalities differed by pain severity (P<0.05). Most patients (70%) had been recommended nonpharmacologic therapy and 40% were currently recommended OTC medications. More patients with moderate (81%) or severe pain (78%) currently received prescription medications, with or without nonpharmacologic therapy, versus those with mild pain (67%). Overall, 47% of patients currently received just one prescription drug, while 49% had received one prescription drug ever. Nonsteroidal anti-inflammatory drugs (NSAIDs) were the most common current (58%) and ever received (88%) prescriptions. Current NSAID prescriptions were not associated with pain severity. Acetaminophen recommendations, opioid prescriptions (current and ever), and multiple prescription medications tried were numerically highest in the severe pain group (all P<0.05 by pain severity). In all groups, >80% of treatment switches were due to lack of efficacy.

Conclusion

Real-life treatment patterns for OA in the US are significantly associated with current patient-reported pain. Combining nonpharmacologic and pharmacologic treatments is common but higher pain ratings are associated with multiple failed prescription treatments. Current use of acetaminophen and opioids, but not NSAIDs, increases alongside pain severity.

Pain severity and healthcare resource utilization in patients with osteoarthritis in the United States

OBJECTIVE

To evaluate healthcare resource utilization (HCRU) by osteoarthritis (OA) pain severity.

METHODS

Cross-sectional surveys of US physicians and their patients were conducted between February and May 2017. Using the Numeric Rating Scale, patients were classified by self-reported pain intensity in the last week into mild (0-3), moderate (4-6), and severe (7-10) cohorts. Parameters assessed included clinical characteristics, HCRU, and current caregiver support. Descriptive statistics were obtained, and analysis of variance and chi-square tests were performed.

RESULTS

Patients (n = 841) were mostly female (60.9%) and white (77.8%), with mean age of 64.6 years. Patients reported mild (45.4%), moderate (35.9%), and severe (18.7%) OA pain. Mean number of affected joints varied by pain severity (range mild: 2.7 to severe: 3.6; p < 0.0001). Pain severity was associated with an increased number of physician-reported and patient-reported overall healthcare provider visits (HCPs; both p < 0.001). As pain increased, patients reported an increased need for mobility aids, accessibility modifications to homes, and help with daily activities due to functional disability. The number of imaging tests used to diagnose OA was similar across pain severity but varied when used for monitoring (X-rays: p < 0.0001; computerized tomography scans: p < 0.0447). Hospitalization rates for OA were low but were significantly associated with pain severity (mild: 4.9%; severe: 11.5%). Emergency department visits were infrequent but increasing pain severity was associated with more prior and planned surgeries.

CONCLUSION

Greater current pain was associated with more prior HCRU including imaging for monitoring progression, HCP visits including more specialty care, hospitalizations, surgery/planned surgery, and loss of independence due to functional disability. Yet rates of hospitalizations and X-ray use were still sizable even among patients with mild pain. These cross-sectional findings warrant longitudinal assessment to further elucidate the impact of pain on HCRU.

Nerve Growth Factor Signaling and Its Contribution to Pain

Nerve growth factor (NGF) is a neurotrophic protein essential for the growth, differentiation, and survival of sympathetic and sensory afferent neurons during development. A substantial body of evidence, based on both animal and human studies, demonstrates that NGF plays a pivotal role in modulation of nociception in adulthood. This has spurred development of a variety of novel analgesics that target the NGF signaling pathway. Here, we present a narrative review designed to summarize how NGF receptor activation and downstream signaling alters nociception through direct sensitization of nociceptors at the site of injury and changes in gene expression in the dorsal root ganglion that collectively increase nociceptive signaling from the periphery to the central nervous system. This review illustrates that NGF has a well-known and multifunctional role in nociceptive processing, although the precise signaling pathways downstream of NGF receptor activation that mediate nociception are complex and not completely understood. Additionally, much of the existing knowledge derives from studies performed in animal models and may not accurately represent the human condition. However, available data establish a role for NGF in the modulation of nociception through effects on the release of inflammatory mediators, nociceptive ion channel/receptor activity, nociceptive gene expression, and local neuronal sprouting. The role of NGF in nociception and the generation and/or maintenance of chronic pain has led to it becoming a novel and attractive target of pain therapeutics for the treatment of chronic pain conditions.

Onset and maintenance of efficacy of subcutaneous tanezumab in patients with moderate to severe osteoarthritis of the knee or hip: A 16-week dose-titration study

OBJECTIVE

To examine the onset and maintenance of efficacy of subcutaneous tanezumab for pain relief and functional improvement in difficult-to-treat patients with moderate-to-severe osteoarthritis (OA) in a 16-week dose-titration study (NCT02697773).

METHODS

Patients were randomized to placebo (placebo group) or tanezumab 2.5 mg at baseline and week 8 (tanezumab 2.5 mg group), or tanezumab 2.5 mg at baseline and tanezumab 5 mg at week 8 (tanezumab 2.5/5 mg group). Analyses included change from baseline in average daily index joint pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain and Physical Function, and treatment responses (WOMAC Pain improvement criteria and Outcome Measures in Rheumatology-Osteoarthritis Research Society International [OMERACT-OARSI] criteria).

RESULTS

The 696 patients received placebo (n = 232), tanezumab 2.5 mg (n = 231), or tanezumab 2.5/5 mg (n = 233). Average daily index joint pain was statistically significantly improved within the first week (day 3-5) with tanezumab 2.5 mg compared with placebo. On first post-randomization WOMAC measurement (week 2), both tanezumab groups had statistically significant improvements compared with placebo in WOMAC Pain and Physical Function, and more tanezumab-treated patients achieved treatment response criteria (≥30%, ≥50%, or ≥70% reduction in WOMAC Pain or OMERACT-OARSI response). Efficacy was generally maintained throughout the 16-week treatment period.

CONCLUSION

Subcutaneous tanezumab provided statistically significant improvements compared with placebo in average daily index joint pain within the first week and WOMAC Pain and Physical Function (week 2) that were generally maintained throughout the 16-week treatment period. Tanezumab 5 mg provided only modest additional efficacy over tanezumab 2.5 mg.

Pooled analysis of tanezumab efficacy and safety with subgroup analyses of phase III clinical trials in patients with osteoarthritis pain of the knee or hip

Purpose

A pooled analysis was conducted to evaluate tanezumab efficacy and safety in patients with osteoarthritis (OA), including subgroup analyses of at-risk patients with diabetes, severe OA symptoms, and those aged ≥65 years.

Patients and methods

Data from phase III placebo-controlled clinical trials of patients with moderate-to-severe OA of the knee or hip were pooled to evaluate tanezumab efficacy (four trials) and safety (nine trials). Patients received intravenous tanezumab, tanezumab plus an oral NSAID (naproxen, celecoxib, or diclofenac), active comparator (naproxen, celecoxib, diclofenac, or oxycodone), or placebo. Efficacy assessments included change from baseline to week 16 in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and physical function scores, Patient’s Global Assessment (PGA) of OA, and percentage of patients with ≥30%, ≥50%, ≥70%, and ≥90% improvement in WOMAC pain. Safety assessments included adverse event (AE) documentation and physical and neurologic examinations.

Results

Tanezumab significantly improved all efficacy end points in the overall population. Efficacy in at-risk patient subgroups was similar to the overall population. Incidence of AEs was highest in the tanezumab plus NSAID group and lowest in the placebo group. Incidence of AEs in the tanezumab monotherapy and active comparator groups was similar. Overall incidence of AEs was similar across subgroups. AEs of abnormal peripheral sensation were more frequently reported in tanezumab-treated patients compared with placebo or active comparator. Patients receiving active comparator had a slightly higher incidence of AEs suggestive of postganglionic sympathetic dysfunction.

Conclusion

Tanezumab consistently provided significant improvement of pain, physical function, and PGA in individuals with OA, including patients with diabetes, severe OA symptoms, or aged ≥65 years. No increased safety risk was observed in at-risk patient subgroups.

Trial registration

NCT00733902, NCT00744471, NCT00830063, NCT00863304, NCT00809354, NCT00864097, NCT00863772, NCT01089725, NCT00985621.

Responsiveness of Single versus Composite Measures of Pain in Knee Osteoarthritis

OBJECTIVE

In rheumatoid arthritis, composite outcomes constructed from a combination of outcome measures are widely used to enhance responsiveness (sensitivity to change) and comprehensively summarize response. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain is the primary outcome measure in many osteoarthritis (OA) trials. Information from other outcomes, such as rescue medication use and other WOMAC subscales, could be added to create composite outcomes, but the sensitivity of such a composite has not been tested.

METHODS

We used data from a completed trial of tanezumab for knee OA (NCT00733902). The WOMAC questionnaire and rescue medication use were measured at several timepoints, up to 16 weeks. Pain and rescue medication outcomes were standardized and combined into 3 composite outcomes through principal components analysis to produce 1 score (composite outcome) and their responsiveness was compared to WOMAC pain, the standard. We pooled all treatment doses of tanezumab into 1 treatment group, for simplicity, and compared this to the control group (placebo).

RESULTS

The composite outcomes showed modestly, but not statistically significantly greater responsiveness when compared to WOMAC pain alone. Adding information on rescue medication to the composite improved responsiveness. While improvements in sensitivity were modest, the required sample sizes for trials using composites was 20-40% less than trials using WOMAC pain alone.

CONCLUSION

Combining information from related but distinct outcomes considered relevant to a particular treatment improved responsiveness, could reduce sample size requirements in OA trials, and might offer a way to better detect treatment efficacy in OA trials.

Participant Preferences for Pharmacologic Chronic Pain Treatment Trial Characteristics: An ACTTION Adaptive Choice-Based Conjoint Study

Barriers to clinical trial recruitment can delay study completion, potentially resulting in increased costs and an unrepresentative sample. In the current study of 150 participants with chronic pain, we used a computerized adaptive choice-based conjoint survey that included 8 characteristics that may affect enrollment in pharmacologic pain treatment trials (ie, treatment allocation, frequency of pain ratings, treatment administration method, current medications, number of study visits, availability of evening and weekend visits, invasiveness of laboratory procedures, payment). These data were analyzed using Sawtooth Software ver. 8.4.8 (Sawtooth Software, Inc, Orem, UT), which identifies the characteristics that dominate participants' decisions across multiple sets of potential trials. Three characteristics had the largest relative importance in participants' trial preferences: 1) invasiveness of required laboratory procedures (ie, 22%), with no procedures or blood tests preferred over ice-water sensory testing or skin biopsy; 2) ability to continue current pain medications (21%); and 3) payment for study participation (21%), with higher payment preferred. The fourth most important characteristic was number of study visits (13%), with participants preferring fewer in-person visits and more phone contacts. Understanding the preferences of potential participants is an important step toward enhancing enrollment in pain treatment trials.

PERSPECTIVE

This article presents the preferences of individuals with chronic pain conditions regarding modifiable pain treatment trial characteristics (eg, number of study visits, payment, treatment allocation). These findings may help to improve enrollment into analgesic clinical trials and in turn accelerate the development of new pain treatments.

Antagonism of nerve growth factor-TrkA signaling and the relief of pain

Nerve growth factor (NGF) was originally discovered as a neurotrophic factor essential for the survival of sensory and sympathetic neurons during development. However, in the adult NGF has been found to play an important role in nociceptor sensitization after tissue injury. The authors outline mechanisms by which NGF activation of its cognate receptor, tropomyosin-related kinase A receptor, regulates a host of ion channels, receptors, and signaling molecules to enhance acute and chronic pain. The authors also document that peripherally restricted antagonism of NGF-tropomyosin-related kinase A receptor signaling is effective for controlling human pain while appearing to maintain normal nociceptor function. Understanding whether there are any unexpected adverse events and how humans may change their behavior and use of the injured/degenerating tissue after significant pain relief without sedation will be required to fully appreciate the patient populations that may benefit from these therapies targeting NGF.

Gabapentin: a pooled analysis of adverse events from three clinical trials in patients with postherpetic neuralgia

BACKGROUND

Gabapentin has been shown to be well tolerated and effective in the management of the pain associated with postherpetic neuralgia (PHN). It is assumed that adverse events occurring with gabapentin are dose related, their frequency and severity increasing with increasing doses.

OBJECTIVE

The aim of this study was to assess the dose dependence of adverse events with gabapentin by determining the relationship between increasing doses of gabapentin and the onset and/or worsening of adverse events in patients with PHN.

METHODS

Data were pooled from 3 randomized, double-blind, placebo-controlled, parallel-group studies of gabapentin that focused on or included patients with PHN. Gabapentin was initiated at 300 mg/d and titrated to maintenance doses of 1800 to 3600 mg/d by day 12 to 24. The analysis of adverse events was based on 3 distinct groups: patients who received gabapentin <1800 mg/d, those who received gabapentin >or=1800 mg/d, and those who received placebo. Patients who were given higher doses of gabapentin had already received lower doses. An adverse event was recorded at the dose of its first onset and recorded again if its severity worsened at a higher dose.

RESULTS

This study included data from 603 patients with PHN: 358 patients (196 [54.7%] women, 162 [45.3%] men; mean [SD] age, 72.3 [10.3] years) received gabapentin, and 245 (133 [54.3%] women, 112 [45.7%] men; mean [SD] age, 73.3 [10.7] years) received placebo. The 3 most common adverse events were dizziness, somnolence, and peripheral edema. Patients receiving gabapentin >or=1800 mg/d had a higher incidence of peripheral edema (7.5%) than those receiving gabapentin <1800 mg/d (1.4%) or placebo (1.6%) (P<0.002, gabapentin >or=1800 mg/d vs placebo). In contrast, the incidence of dizziness and somnolence was not higher in patients receiving gabapentin >or=1800 mg/d compared with those in the other groups. Compared with placebo recipients, patients receiving gabapentin <1800 mg/d reported a significantly greater frequency of dizziness (20.2% gabapentin <1800 mg/d vs 7.4% placebo; P<0.002) and somnolence (14.9% vs 5.8%, respectively; P=0.005). However, at >or=1800 mg/d, rates of dizziness (9.7%) and somnolence (6.9%) were comparable to those with placebo. Discontinuation rates were comparable between patients receiving gabapentin and those receiving placebo.

CONCLUSIONS

In this pooled analysis of adverse-event data from 3 clinical trials in patients with PHN, the incidence of peripheral edema was increased when gabapentin was titrated to >or=1800 mg/d. Dizziness and somnolence, the other most commonly occurring adverse events, were transient and did not occur more frequently or worsen with titration to >or=1800 mg/d. Based on these findings, it does not appear that safety concerns should limit titration of gabapentin to achieve optimal efficacy.

Celecoxib clinical profile

Celecoxib is the first COX-2-specific inhibitor approved for relief of the signs and symptoms of osteoarthritis (OA) and rheumatoid arthritis (RA), as well as for treatment of familial adenomatous polyposis. For both OA and RA, celecoxib has been shown to be significantly superior in efficacy to placebo and similar in efficacy to traditional non-steroidal anti-inflammatory drugs. Its advantage, however, is its gastrointestinal (GI) safety. Randomized clinical trials as well as long-term outcomes studies have demonstrated that the GI safety profile of celecoxib is superior to that of traditional NSAIDs and similar to that of placebo. Additionally, the renal and cardiovascular safety of celecoxib has also become apparent, as well as its efficacy, tolerability and safety in the elderly population.

Kappa 3 receptors and levorphanol-induced analgesia

Levorphanol is a widely used opiate analgesic. Although structurally related to morphine, levorphanol has high affinity for a number of receptor subtypes, including both kappa 1 and kappa 3. Prior reports had implicated a kappa component of levorphanol-induced antinociception. Evidence is now presented suggesting that levorphanol-induced analgesia is produced by a mixture of mu and kappa 3 mechanisms. Levorphanol was a potent analgesic in the tail-flick assay, when given systemically, spinally or supraspinally. Isobolographic analysis of the combined administration of levorphanol, spinally and supraspinally implied synergistic interactions. Naloxonazine reduced levorphanol-induced analgesia, implicating a role for mu1 receptors. The kappa 1 antagonist nor-binaltorphimine at a dose which reversed analgesia induced by U50,488H did not antagonize levorphanol-induced analgesia. Additional studies revealed no cross tolerance in either direction, between levorphanol with the kappa 1 analgesic U50,488H. Together, these results strongly argue against a role for kappa 1 receptors in levorphanol-induced analgesia. However, mice tolerant to the kappa 3 analgesic, naloxone benzoylhydrazone (NalBzoH), showed cross tolerance to levorphanol, implying a role of kappa 3 mechanisms in levorphanol-induced analgesia.