Vladimir Skljarevski

Duloxetine, a centrally acting analgesic, in the treatment of patients with osteoarthritis knee pain: a 13-week, randomized, placebo-controlled trial.

ABSTRACT Pain is a common cause of disability in osteoarthritis. Duloxetine, a serotonin and norepinephrine reuptake inhibitor (SNRI), has demonstrated analgesic effects in diabetic peripheral neuropathy and fibromyalgia. Considering its central mechanism of action, duloxetine may be effective in other pain states with evidence of central sensitization. Herein, we report the results of a 13‐week, randomized, double‐blind, placebo‐controlled trial of duloxetine (60–120 mg/day) versus placebo in the treatment of knee pain in 231 patients meeting clinical and radiographic criteria for osteoarthritis of the knee. Duloxetine was superior to placebo on the primary efficacy measure (weekly mean 24‐h pain scores) beginning at Week 1 and continuing through the treatment period (P ⩽ .05). There was also a significant improvement in the WOMAC physical functioning subscale and several other secondary outcomes. Adverse‐event rates did not differ significantly between treatment groups (49.5% for duloxetine 60–120 mg/day, and 40.8% for placebo).

The nociceptive flexion reflex in humans – review article

&NA; The nociceptive flexion reflex (NFR) is a physiological, polysynaptic reflex allowing for painful stimuli to activate an appropriate withdrawal response. NFR is easily measurable in clinical setting, and is a reliable and objective tool for measurement of an individual’s pain experience. An exhaustive review of the literature, covering multiple search engines, indicates that the NFR method is valuable in studying the impact of diverse pharmacological and non‐pharmacological interventions on the flexion reflex, in conditions of acute pain and in healthy volunteers. More recently, the NFR method has gained particular attention as a research tool in studies of central sensitization and persistent or chronic pain.

Considerations for improving assay sensitivity in chronic pain clinical trials: IMMPACT recommendations

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.

Duloxetine Versus Placebo in Patients With Chronic Low Back Pain: A 12-Week, Fixed-Dose, Randomized, Double-Blind Trial

UNLABELLED This randomized, double-blind, placebo-controlled study assessed efficacy and safety of duloxetine in patients with chronic low back pain (CLBP). Adults (n = 401) with a nonneuropathic CLBP and average pain intensity of ≥ 4 on an 11-point numerical scale (Brief Pain Inventory [BPI]) were treated with either duloxetine 60 mg once daily or placebo for 12 weeks. The primary measure was BPI average pain. Secondary endpoints included Patients Global Impressions of Improvement (PGI-I), Roland Morris Disability Questionnaire (RMDQ-24), BPI-Severity (BPI-S), BPI-Interference (BPI-I), and response rates (either ≥ 30% or ≥ 50% BPI average pain reduction at endpoint). Health outcomes included Short Form-36, European Quality of Life-5 Dimensions, and the Work Productivity and Activity Impairment questionnaire. Safety and tolerability were assessed. Compared with placebo-treated patients, duloxetine-treated patients reported a significantly greater reduction in BPI average pain (P ≤ .001). Similarly, duloxetine-treated patients reported significantly greater improvements in PGI-I, BPI-S, BPI-I, 50% response rates, and some health outcomes. The RMDQ and 30% response rate showed numerical improvements with duloxetine treatment. Significantly more patients in the duloxetine group (15.2%) than patients in the placebo group (5.4%) discontinued because of adverse events (P = .002). Nausea and dry mouth were the most common treatment-emergent adverse events with rates significantly higher in duloxetine-treated patients. PERSPECTIVE This study provides clinical evidence of the efficacy and safety of duloxetine at a fixed dose of 60 mg once daily in the treatment of chronic low back pain (CLBP). As of December 2009, duloxetine has not received regulatory approval for the treatment of CLBP.

Efficacy and safety of duloxetine in patients with chronic low back pain.

Study Design. This was a randomized, double-blind, placebo-controlled clinical trial. Objective. To assess the efficacy and safety of duloxetine in the treatment of chronic low back pain (CLBP). Summary of Background Data. Imbalance of serotonin and norepinephrine within modulatory pain pathways has been implicated in the development and maintenance of chronic pain. Duloxetine, a selective reuptake inhibitor of serotonin and norepinephrine, has demonstrated clinical efficacy in 3 distinct chronic pain conditions: diabetic peripheral neuropathic pain, fibromyalgia, and chronic pain because of osteoarthritis. Methods. In this randomized double-blind trial, adult nondepressed patients with a non-neuropathic CLBP and a weekly mean of the 24-hour average pain score ≥4 at baseline (0–10 scale) were treated with either duloxetine or placebo for 13 weeks. The dose of duloxetine during first 7 weeks was 60 mg once daily. At week 7, patients reporting <30% pain reduction had their dose increased to 120 mg. The primary outcome measure was the Brief Pain Inventory (BPI) 24-hour average pain rating. Secondary measures included Roland-Morris Disability Questionnaire-24; Patients Global Impressions of Improvement; Clinical Global Impressions-Severity (CGI-S); BPI-Severity and -Interference (BPI-I); and weekly means of the 24-hour average pain, night pain, and worst pain scores from patient diaries. Quality-of-life, safety, and tolerability outcomes were also assessed. Results. Compared with placebo-treated patients (least-squares mean change of −1.50), patients on duloxetine (least-squares mean change of −2.32) had a significantly greater reduction in the BPI 24-hour average pain from baseline to endpoint (P = 0.004 at week 13). Additionally, the duloxetine group significantly improved on Patients Global Impressions of Improvement; Roland-Morris Disability Questionnaire-24; BPI-Severity and average BPI-Interference; weekly mean of the 24-hour average pain, night pain, and worst pain. Significantly more patients in the duloxetine group (13.9%) compared with placebo (5.8%) discontinued because of adverse events (P = 0.047). The most common treatment-emergent adverse events in the duloxetine group included nausea, dry mouth, fatigue, diarrhea, hyperhidrosis, dizziness, and constipation. Conclusion. Duloxetine significantly reduced pain and improved functioning in patients with CLBP. The safety and tolerability were similar to those reported in earlier studies.

Duloxetine and pregabalin: High-dose monotherapy or their combination? The ''COMBO-DN study'' - a multinational, randomized, double-blind, parallel-group study in patients with diabetic peripheral neuropathic pain

Summary Combination of the standard doses of duloxetine and pregabalin was not superior to the maximum dose of either drug in patients with painful diabetic neuropathy. Abstract This multicentre, double‐blind, parallel‐group study in diabetic peripheral neuropathic pain addressed whether, in patients not responding to standard doses of duloxetine or pregabalin, combining both medications is superior to increasing each drug to its maximum recommended dose. For initial 8‐week therapy, either 60 mg/day duloxetine (groups 1, 2) or 300 mg/day pregabalin (groups 3, 4) was given. Thereafter, in the 8‐week combination/high‐dose therapy period, only nonresponders received 120 mg/day duloxetine (group 1), a combination of 60 mg/day duloxetine and 300 mg/day pregabalin (groups 2, 3), or 600 mg/day pregabalin (group 4). Primary outcome (Brief Pain Inventory Modified Short Form [BPI‐MSF] 24‐hour average pain change after combination/high‐dose therapy) was analyzed comparing combination (groups 2, 3 pooled) with high‐dose monotherapy (groups 1, 4 pooled). Secondary end points included response rates, BPI‐MSF severity items, and comparison of duloxetine and pregabalin in BPI‐MSF average pain. Eight hundred four patients were evaluated for initial therapy and 339 for combination/high‐dose therapy. There were no significant differences between combination and high‐dose monotherapy regarding BPI‐MSF average pain (mean change: combination: −2.35; high‐dose monotherapy: −2.16; P = 0.370) and most secondary end points, which, however, consistently favoured combination therapy. Fifty‐percent response rates were 52.1% for combination and 39.3% for high‐dose monotherapy (P = 0.068). In exploratory analyses of the initial 8‐week therapy uncorrected for multiple comparisons, 60 mg/day duloxetine was found superior to 300 mg/day pregabalin (P < 0.001). Both drugs and their combination were well tolerated. Although not significantly superior to high‐dose monotherapy, combination therapy was considered to be effective, safe, and well tolerated.

Duloxetine use in chronic painful conditions – individual patient data responder analysis

Duloxetine has been studied in four distinct chronic pain conditions – osteoarthritis (OA), fibromyalgia, chronic low back pain (CLBP) and diabetic peripheral neuropathic pain (DPNP). These trials have involved large numbers of patients with at least moderate pain, and have used similar methods for recording pain intensity, over about 12 weeks.

Duloxetine, Pregabalin, and Duloxetine Plus Gabapentin for Diabetic Peripheral Neuropathic Pain Management in Patients With Inadequate Pain Response to Gabapentin: An Open-Label, Randomized, Noninferiority Comparison

OBJECTIVE To determine whether duloxetine is noninferior to (as good as) pregabalin in the treatment of pain associated with diabetic peripheral neuropathy. PATIENTS AND METHODS We performed a 12-week, open-label study of patients with diabetic peripheral neuropathic pain who had been treated with gabapentin (≥ 900 mg/d) and had an inadequate response (defined as a daily pain score of ≥ 4 on a numerical rating scale [0-10 points]). The first patient was enrolled on September 28, 2006, and the last patient visit occurred on August 26, 2009. Patients were randomized to duloxetine monotherapy (n=138), pregabalin monotherapy (n=134), or a combination of duloxetine and gabapentin (n=135). The primary objective was a noninferiority comparison between duloxetine and pregabalin on improvement in the weekly mean of the diary-based daily pain score (0- to 10-point scale) at end point. Noninferiority would be declared if the mean improvement for duloxetine was no worse than the mean improvement for pregabalin, within statistical variability, by a margin of -0.8 unit. RESULTS The mean change in the pain rating at end point was -2.6 for duloxetine and -2.1 for pregabalin. The 97.5% lower confidence limit was a -0.05 difference in means, establishing noninferiority. As to adverse effects, nausea, insomnia, hyperhidrosis, and decreased appetite were more frequent with duloxetine than pregabalin; insomnia, more frequent with duloxetine than duloxetine plus gabapentin; peripheral edema, more frequent with pregabalin than with duloxetine; and nausea, hyperhidrosis, decreased appetite, and vomiting, more frequent with duloxetine plus gabapentin than with pregabalin. CONCLUSION Duloxetine was noninferior to pregabalin for the treatment of pain in patients with diabetic peripheral neuropathy who had an inadequate pain response to gabapentin. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00385671.

5-HT1F receptor agonists in acute migraine treatment: a hypothesis

Serotonin-1F receptor (5-HT1F) agonists may relieve acute migraine without vasoconstriction. We conducted a review of preclinical and clinical data that assessed the potential link between migraine and 5-HT1F activation. (i) A high correlation exists between the potency of various 5-HT1 receptor agonists in the guinea pig dural plasma protein extravasation assay and their 5-HT1F receptor binding affinity. (ii) 5-HT1F receptors are on the trigeminal system, and may participate in blocking migraine pain transmission through the trigeminal ganglion and nucleus caudalis. (iii) 5-HT1F receptors are located on glutamate-containing neurones and their activation might inhibit glutamate release; glutamate excess may play a role in migraine. (iv) Selective 5-HT1F receptor agonists (LY334370; LY344864) are effective in preclinical migraine models and are non-vasoconstrictive. (v) LY334370 is effective in acute migraine, and does not cause any symptoms/signs of coronary vasoconstriction. Preclinical experiments and clinical observations argue for a role of selective 5-HT1F agonists in migraine.

Neuropathic pain phenotyping as a predictor of treatment response in painful diabetic neuropathy: data from the randomized, double-blind, COMBO-DN study.

&NA; Duloxetine and pregabalin have different effects on neuropathic pain components. This might explain differential responses to these drugs when given either alone or in combination. &NA; Sensory profiles are heterogeneous in neuropathic pain disorders, and subgroups of patients respond differently to treatment. To further explore this, patients in the COMBO‐DN study were prospectively assessed by the Neuropathic Pain Symptom Inventory (NPSI) at baseline, after initial 8‐week therapy with either duloxetine or pregabalin, and after subsequent 8‐week combination/high‐dose therapy. Exploratory post hoc cluster analyses were performed to identify and characterize potential subgroups through their scores in the NPSI items. In patients not responding to initial 60 mg/d duloxetine, adding 300 mg/d pregabalin for combination treatment was particularly effective regarding the dimensions pressing pain and evoked pain, whereas maximizing the duloxetine dose to 120 mg/d appeared more beneficial regarding paresthesia/dysesthesia. In contrast, adding 60 mg/d duloxetine to 300 mg/d pregabalin in case of nonresponse to initial pregabalin led to numerically higher decreases in all NPSI dimensions/items compared to maximizing the pregabalin dose to 600 mg/d. Cluster analysis revealed 3 patient clusters (defined by baseline scores for the 10 NPSI sensory items) with different pain profiles, not only in terms of overall pain severity, but also across NPSI items. Mean Brief Pain Inventory average pain improved in all clusters during combination/high‐dose therapy. However, in patients with severe pain, the treatment effect showed a trend in favor of high‐dose monotherapy, whereas combination therapy appeared to be more beneficial in patients with moderate and mild pain (not significant). These complementary exploratory analyses further endorse the idea that sensory phenotyping might lead to a more stratified treatment and potentially to personalized pain therapy.