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      Duloxetine 60 mg for chronic low back pain: post hoc responder analysis of double-blind, placebo-controlled trials

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          Abstract

          Introduction

          Duloxetine has demonstrated efficacy in chronic low back pain (CLBP). We examined the predictors of response to duloxetine for CLBP.

          Patients and methods

          This was a post hoc analysis of pooled data from 4 double-blind, ran-domized, placebo-controlled trials of duloxetine (60 mg/day for 12–14 weeks) in adult patients with CLBP. Primary outcome was proportion of patients with ≥30% reduction in Brief Pain Inventory (BPI) average pain (“pain reduction”) at 12–14 weeks. The proportion of patients with ≥30% and ≥50% (secondary outcome) pain reduction in duloxetine and placebo groups was compared. Variables for responder analyses were early improvement (≥15% pain reduction at Week 2), sex, age, baseline BPI average pain score, duration of CLBP, and number of painful body sites according to the Michigan Body Map (≥2 vs 1 [isolated CLBP]; 1 trial); relative risk (RR) and 95% confidence interval (CI) were calculated.

          Results

          Compared with placebo (n = 653), a greater proportion of duloxetine-treated patients (n = 642) achieved ≥30% (59.7% vs 47.8%; P < 0.001) and ≥50% pain reduction (48.6% vs 35.1%; P < 0.001). Among duloxetine-treated patients, early improvement was associated with greater likelihood of ≥30% (RR [95% CI], 2.91 [2.30–3.67]) or ≥50% (3.24 [2.44–4.31]) pain reduction. Women were slightly more likely than men to achieve ≥30% (RR [95% CI], 1.14 [1.00–1.30]) or ≥50% (1.17 [0.99–1.38]) pain reduction. Response rates were similar between age, CLBP duration, and baseline BPI average pain score subgroups. Patients with ≥2 painful sites were more likely to respond to duloxetine 60 mg relative to placebo than patients with isolated CLBP (RR, duloxetine vs placebo [95% CI]: ≥30% reduction, ≥2 painful sites 1.40 [1.18–1.66], isolated CLBP 1.07 [0.78–1.48]; ≥50% reduction, ≥2 painful sites 1.51 [1.20–1.89], isolated CLBP 1.23 [0.81–1.88]).

          Conclusion

          Early pain reduction was indicative of overall response. Patients with multiple painful sites had more benefit from duloxetine than patients with isolated CLBP.

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          Most cited references 22

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          Evidence of augmented central pain processing in idiopathic chronic low back pain.

          For many individuals with chronic low back pain (CLBP), there is no identifiable cause. In other idiopathic chronic pain conditions, sensory testing and functional magnetic resonance imaging (fMRI) have identified the occurrence of generalized increased pain sensitivity, hyperalgesia, and altered brain processing, suggesting central augmentation of pain processing in such conditions. We compared the results of both of these methods as applied to patients with idiopathic CLBP (n = 11), patients with widespread pain (fibromyalgia; n = 16), and healthy control subjects (n = 11). Patients with CLBP had low back pain persisting for at least 12 months that was unexplained by MRI/radiographic changes. Experimental pain testing was performed at a neutral site (thumbnail) to assess the pressure-pain threshold in all subjects. For fMRI studies, stimuli of equal pressure (2 kg) and of equal subjective pain intensity (slightly intense pain) were applied to this same site. Despite low numbers of tender points in the CLBP group, experimental pain testing revealed hyperalgesia in this group as well as in the fibromyalgia group; the pressure required to produce slightly intense pain was significantly higher in the controls (5.6 kg) than in the patients with CLBP (3.9 kg) (P = 0.03) or the patients with fibromyalgia (3.5 kg) (P = 0.006). When equal amounts of pressure were applied to the 3 groups, fMRI detected 5 common regions of neuronal activation in pain-related cortical areas in the CLBP and fibromyalgia groups (in the contralateral primary and secondary [S2] somatosensory cortices, inferior parietal lobule, cerebellum, and ipsilateral S2). This same stimulus resulted in only a single activation in controls (in the contralateral S2 somatosensory cortex). When subjects in the 3 groups received stimuli that evoked subjectively equal pain, fMRI revealed common neuronal activations in all 3 groups. At equal levels of pressure, patients with CLBP or fibromyalgia experienced significantly more pain and showed more extensive, common patterns of neuronal activation in pain-related cortical areas. When stimuli that elicited equally painful responses were applied (requiring significantly lower pressure in both patient groups as compared with the control group), neuronal activations were similar among the 3 groups. These findings are consistent with the occurrence of augmented central pain processing in patients with idiopathic CLBP.
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            Central pain mechanisms in chronic pain states--maybe it is all in their head.

            Mechanisms underlying chronic pain differ from those underlying acute pain. In chronic pain states, central nervous system (CNS) factors appear to play particularly prominent roles. In the absence of anatomical causes of persistent pain, medical sub-specialities have historically applied wide-ranging labels (e.g., fibromyalgia (FM), irritable bowel syndrome, interstitial cystitis and somatisation) for what now is emerging as a single common set of CNS processes. The hallmark of these 'centrally driven' pain conditions is a diffuse hyperalgesic state identifiable using experimental sensory testing, and corroborated by functional neuroimaging. The characteristic symptoms of these central pain conditions include multifocal pain, fatigue, insomnia, memory difficulties and a higher rate of co-morbid mood disorders. In contrast to acute and peripheral pain states that are responsive to non-steroidal anti-inflammatory drugs (NSAIDs) and opioids, central pain conditions respond best to CNS neuromodulating agents, such as serotonin-norepinephrine reuptake inhibitors (SNRIs) and anticonvulsants. Copyright © 2011 Elsevier Ltd. All rights reserved.
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              Prevalence and characteristics of chronic musculoskeletal pain in Japan

              Background This cross-sectional study was conducted to obtain epidemiologic data on chronic musculoskeletal pain in the Japanese people, and with it a better understanding of the actual conditions and problems involved. Methods A questionnaire covering basic information, chronic musculoskeletal pain, daily life, quality of life, and social loss was prepared and mailed to 11507 individuals aged 18 years or older. Subjects were selected randomly nationwide in accordance with the demographic composition of Japan. Results The prevalence of chronic musculoskeletal pain was 15.4%. The prevalence was highest in people in their 30s to 50s. Pain occurred most frequently in the low back, neck, shoulder, and knee. Among symptomatic subjects, 42% sought treatment, by visiting a medical institution (19%), taking folk remedies (20%), or both (3%). Treatment was generally prolonged, with 70% of those treated reporting treatment durations of more than a year. Although 69% reported that their symptoms had improved, 30% reported unchanged or aggravated symptoms and dissatisfaction with treatment. Among symptomatic subjects, a high percentage of both men and women had lost jobs, left school, been absent from work or school, or had changed jobs. Basic activities of daily living (ADL) were disturbed in men, and the instrumental ADL (IADL) score was low in women. SF-36 scale scores were significantly lower in every area for subjects with chronic pain. Conclusions Chronic musculoskeletal pain does not necessarily improve even with prolonged treatment. It adversely affects daily life and both physical and mental health. Because those suffering pain often increasingly need assistance in daily activities, people around them are also affected. The therapeutic system and treatment procedures for chronic musculoskeletal pain merit prompt review.
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                Author and article information

                Journal
                J Pain Res
                J Pain Res
                Journal of Pain Research
                Journal of Pain Research
                Dove Medical Press
                1178-7090
                2017
                24 July 2017
                : 10
                : 1723-1731
                Affiliations
                [1 ]Bio-Medicine
                [2 ]Statistical Science
                [3 ]Scientific Communications, Medicines Development Unit, Eli Lilly Japan K.K., Kobe
                [4 ]Clinical Research Development
                [5 ]Medical Affairs Department, Shionogi & Co. Ltd, Osaka
                [6 ]Department of Orthopedic Surgery, Fukushima Medical University, Fukushima, Japan
                Author notes
                Correspondence: Hiroyuki Enomoto, Bio-Medicine, Medicines Development Unit, Eli Lilly Japan K.K., 7-1-5 Isogamidori, Chuo-Ku, Kobe 651-0086, Japan, Tel +81 3 5574 9143, Fax +81 3 5574 9979, Email enomoto_hiroyuki@ 123456lilly.com
                Article
                jpr-10-1723
                10.2147/JPR.S138297
                5533563
                © 2017 Alev et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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