Study protocol for a randomised, double-blind, placebo-controlled clinical trial of duloxetine for the treatment and prevention of musculoskeletal pain: altering the transition from acute to chronic pain (ATTAC pain)

Effectiveness of Duloxetine on Oxaliplatin-induced Allodynia and Hyperalgesia in Rats

Development of painful oxaliplatin-induced peripheral neuropathy (OIPN) is a major problem in people who receive oxaliplatin as part of cancer treatment. The pain experienced by those with OIPN can be seriously debilitating and lead to discontinuation of an otherwise successful treatment. Duloxetine is currently the only recommended treatment for established painful OIPN recommended by the American Society of Clinical Oncology, but its preventative ability is still not clear. This study examined the ability of duloxetine to prevent signs of chronic OIPN in female (n = 12) and male (n = 21) rats treated with the chemotherapeutic agent oxaliplatin. Using an established model of OIPN, rats were started on duloxetine (15 mg) one week prior to oxaliplatin administration and continued duloxetine for 32 days. Behavioral testing for mechanical allodynia and mechanical hyperalgesia was done with selected von Frey filaments. Significant posttreatment differences were found for allodynia in female (p = .004), but not male rats. Duloxetine was associated with significant differences for hyperalgesia in both female (p < .001) and male (p < .001) rats. These findings provide preliminary evidence of the preventative effects of duloxetine on both oxaliplatin-induced allodynia and hyperalgesia in male and female rats, with a difference noted in response between the sexes.

Antidepressants for pain management in adults with chronic pain: a network meta-analysis

BACKGROUND

Chronic pain is common in adults, and often has a detrimental impact upon physical ability, well-being, and quality of life. Previous reviews have shown that certain antidepressants may be effective in reducing pain with some benefit in improving patients' global impression of change for certain chronic pain conditions. However, there has not been a network meta-analysis (NMA) examining all antidepressants across all chronic pain conditions.

OBJECTIVES

To assess the comparative efficacy and safety of antidepressants for adults with chronic pain (except headache).

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, AMED and PsycINFO databases, and clinical trials registries, for randomised controlled trials (RCTs) of antidepressants for chronic pain conditions in January 2022.

SELECTION CRITERIA

We included RCTs that examined antidepressants for chronic pain against any comparator. If the comparator was placebo, another medication, another antidepressant, or the same antidepressant at different doses, then we required the study to be double-blind. We included RCTs with active comparators that were unable to be double-blinded (e.g. psychotherapy) but rated them as high risk of bias. We excluded RCTs where the follow-up was less than two weeks and those with fewer than 10 participants in each arm.  DATA COLLECTION AND ANALYSIS: Two review authors separately screened, data extracted, and judged risk of bias. We synthesised the data using Bayesian NMA and pairwise meta-analyses for each outcome and ranked the antidepressants in terms of their effectiveness using the surface under the cumulative ranking curve (SUCRA). We primarily used Confidence in Meta-Analysis (CINeMA) and Risk of Bias due to Missing Evidence in Network meta-analysis (ROB-MEN) to assess the certainty of the evidence. Where it was not possible to use CINeMA and ROB-MEN due to the complexity of the networks, we used GRADE to assess the certainty of the evidence. Our primary outcomes were substantial (50%) pain relief, pain intensity, mood, and adverse events. Our secondary outcomes were moderate pain relief (30%), physical function, sleep, quality of life, Patient Global Impression of Change (PGIC), serious adverse events, and withdrawal.

MAIN RESULTS

This review and NMA included 176 studies with a total of 28,664 participants. The majority of studies were placebo-controlled (83), and parallel-armed (141). The most common pain conditions examined were fibromyalgia (59 studies); neuropathic pain (49 studies) and musculoskeletal pain (40 studies). The average length of RCTs was 10 weeks. Seven studies provided no useable data and were omitted from the NMA. The majority of studies measured short-term outcomes only and excluded people with low mood and other mental health conditions. Across efficacy outcomes, duloxetine was consistently the highest-ranked antidepressant with moderate- to high-certainty evidence. In duloxetine studies, standard dose was equally efficacious as high dose for the majority of outcomes. Milnacipran was often ranked as the next most efficacious antidepressant, although the certainty of evidence was lower than that of duloxetine. There was insufficient evidence to draw robust conclusions for the efficacy and safety of any other antidepressant for chronic pain.  Primary efficacy outcomes Duloxetine standard dose (60 mg) showed a small to moderate effect for substantial pain relief (odds ratio (OR) 1.91, 95% confidence interval (CI) 1.69 to 2.17; 16 studies, 4490 participants; moderate-certainty evidence) and continuous pain intensity (standardised mean difference (SMD) -0.31, 95% CI -0.39 to -0.24; 18 studies, 4959 participants; moderate-certainty evidence). For pain intensity, milnacipran standard dose (100 mg) also showed a small effect (SMD -0.22, 95% CI -0.39 to 0.06; 4 studies, 1866 participants; moderate-certainty evidence). Mirtazapine (30 mg) had a moderate effect on mood (SMD -0.5, 95% CI -0.78 to -0.22; 1 study, 406 participants; low-certainty evidence), while duloxetine showed a small effect (SMD -0.16, 95% CI -0.22 to -0.1; 26 studies, 7952 participants; moderate-certainty evidence); however it is important to note that most studies excluded participants with mental health conditions, and so average anxiety and depression scores tended to be in the 'normal' or 'subclinical' ranges at baseline already. Secondary efficacy outcomes Across all secondary efficacy outcomes (moderate pain relief, physical function, sleep, quality of life, and PGIC), duloxetine and milnacipran were the highest-ranked antidepressants with moderate-certainty evidence, although effects were small. For both duloxetine and milnacipran, standard doses were as efficacious as high doses. Safety There was very low-certainty evidence for all safety outcomes (adverse events, serious adverse events, and withdrawal) across all antidepressants. We cannot draw any reliable conclusions from the NMAs for these outcomes.

AUTHORS' CONCLUSIONS

Our review and NMAs show that despite studies investigating 25 different antidepressants, the only antidepressant we are certain about for the treatment of chronic pain is duloxetine. Duloxetine was moderately efficacious across all outcomes at standard dose. There is also promising evidence for milnacipran, although further high-quality research is needed to be confident in these conclusions. Evidence for all other antidepressants was low certainty. As RCTs excluded people with low mood, we were unable to establish the effects of antidepressants for people with chronic pain and depression. There is currently no reliable evidence for the long-term efficacy of any antidepressant, and no reliable evidence for the safety of antidepressants for chronic pain at any time point.

Tolerability and efficacy of duloxetine for the prevention of persistent musculoskeletal pain after trauma and injury: a pilot three-group randomized controlled trial

ABSTRACT

This study investigated the tolerability and preliminary efficacy of duloxetine as an alternative nonopioid therapeutic option for the prevention of persistent musculoskeletal pain (MSP) among adults presenting to the emergency department with acute MSP after trauma or injury. In this randomized, double-blind, placebo-controlled study, eligible participants (n = 78) were randomized to 2 weeks of a daily dose of one of the following: placebo (n = 27), 30 mg duloxetine (n = 24), or 60 mg duloxetine (n = 27). Tolerability, the primary outcome, was measured by dropout rate and adverse effects. Secondary outcomes assessed drug efficacy as measured by (1) the proportion of participants with moderate to severe pain (numerical rating scale ≥ 4) at 6 weeks (pain persistence); and (2) average pain by group over the six-week study period. We also explored treatment effects by type of trauma (motor vehicle collision [MVC] vs non-MVC). In both intervention groups, duloxetine was well tolerated and there were no serious adverse events. There was a statistically significant difference in pain over time for the 60 mg vs placebo group ( P = 0.03) but not for the 30 mg vs placebo group ( P = 0.51). In both types of analyses, the size of the effect of duloxetine was larger in MVC vs non-MVC injury. Consistent with the role of stress systems in the development of chronic pain after traumatic stress, our data indicate duloxetine may be a treatment option for reducing the transition from acute to persistent MSP. Larger randomized controlled trials are needed to confirm these promising results.

Clinical Interpretation of Self-Reported Pain Scores in Children with Acute Pain

OBJECTIVE

To identify self-reported pain scores that best represent categories of no pain, mild, moderate, and severe pain in children, and a pain score that accurately represents a child's perceived need for medication, that is, a minimum pain score at which a child would want an analgesic.

STUDY DESIGN

Prospective cross-sectional cohort study of children aged 6-17 years presenting to a pediatric emergency department with painful and nonpainful conditions. Pain was measured using the 10-point Verbal Numerical Rating Scale. Receiver operating characteristic -based methodology was used to determine pain scores that best differentiated no pain from mild pain, mild pain from moderate pain, and moderate pain from severe pain. Descriptive statistics were used to determine the perceived need for medication.

RESULTS

We analyzed data from 548 children (51.3% female, 61.9% with a painful condition). The scores that best represent categories of pain intensity are as follows: 0-1 for no pain; 2-5 for mild pain; 6-7 for moderate pain; and 8-10 for severe pain. The area under the curve for the cut points differentiating each category ranged from 0.76 to 0.88. The median pain score representing the perceived need for medication was 6 (IQR, 4-7; range, 0-10).

CONCLUSIONS

We identified population-level self-reported pain scores in children associated with categories of pain intensity that differ from scores conventionally used. Implementing our findings may provide a more accurate representation of the clinical meaning of pain scores and reduce selection bias in research. Our findings do not support the use of pain scores in isolation for clinical decision making or the use of a pain score threshold to represent a child's perceived need for medication.

Duloxetine suppresses BMP-4-induced release of osteoprotegerin via inhibition of the SMAD signaling pathway in osteoblasts

Duloxetine, a selective serotonin-norepinephrine reuptake inhibitor, is currently recommended for the treatment of chronic painful disorders such as fibromyalgia, chronic musculoskeletal pain, and diabetic peripheral neuropathy. We previously demonstrated that bone morphogenetic protein-4 (BMP-4) stimulates osteoprotegerin (OPG) production in osteoblast-like MC3T3-E1 cells, and that p70 S6 kinase positively regulates OPG synthesis. The present study aimed to investigate the effect of duloxetine on BMP-4-stimulated OPG synthesis in these cells. Duloxetine dose-dependently suppressed OPG release stimulated by BMP-4. Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), reduced BMP-4-stimulated OPG release, whereas a selective and specific norepinephrine reuptake inhibitor, reboxetine, failed to affect OPG release. In addition, another SSRI sertraline also inhibited BMP-4-stimulated OPG release. On the other hand, siRNA of SMAD1 reduced the OPG release stimulated by BMP-4, indicating the involvement of the SMAD1/5/8 pathway in OPG release. Rapamycin inhibited BMP-4-stimulated p70 S6 kinase phosphorylation, and compound C suppressed the SMAD1/5/8 phosphorylation stimulated by BMP-4. Duloxetine did not affect BMP-4-induced phosphorylation of p70 S6 kinase but suppressed SMAD1/5/8 phosphorylation. Both fluvoxamine and sertraline also inhibited BMP-4-elicited phosphorylation of SMAD1/5/8. These results strongly suggest that duloxetine suppresses BMP-4-stimulated OPG release via inhibition of the Smad1/5/8 signaling pathway in osteoblasts.