Effectiveness of Milnacipran for the Treatment of Chronic Pain

A double-blind, placebo-controlled, parallel-group pilot study of milnacipran for chronic radicular pain (sciatica) associated with lumbosacral disc disease

OBJECTIVE

The current study investigates whether milnacipran, an equipotent serotonin-norepinephrine reuptake inhibitor, is effective in reducing chronic radicular pain in patients (N = 11) with lumbosacral disc disease.

METHOD

This study is a 10-week randomized, parallel-group, double-blind, placebo-controlled trial of milnacipran (100-200 mg/d, dosed twice a day). Subjects (enrolled from October 2010 to September 2011 through the Duke University Pain and Palliative Care Clinic, Durham, North Carolina) included patients with radiologically confirmed disc disease with nerve root compression. The primary outcome measure was radicular pain measured by visual analog scale score (VAS-Rad); patients were asked to specifically rate radicular pain ("shooting or electrical or prickly pain in 1 or both legs"). Secondary outcome measures included nociceptive low back pain by visual analog scale (VAS-Noc), Oswestry Low Back Pain Disability Questionnaire, Neuropathic Pain Questionnaire, Medical Outcomes Study (MOS) 36-Item Short-Form Health Survey, Beck Depression Inventory, and State-Trait Anxiety Inventory. Between-group changes in outcome measures between baseline and endpoint were analyzed using Mann-Whitney U nonparametric measure of central tendency.

RESULTS

Milnacipran treatment yielded statistically significant reduction in radicular pain (VAS-Rad, P = .01) and nociceptive low back pain (VAS-Noc, P = .04) compared to placebo. No statistically significant between-group differences were observed in the other secondary outcome measures.

CONCLUSIONS

In this small pilot study, milnacipran treatment was associated with reduction in radicular and nociceptive low back pain in patients with lumbosacral disc disease. Larger studies of milnacipran in this population are warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01777581.

Open-label milnacipran for patients with persistent knee pain 1 year or longer after total knee arthroplasty: a pilot study

OBJECTIVE

The current study investigates whether milnacipran is effective in reducing pain and improving function in patients with persistent pain ≥ 1 year after total knee arthroplasty.

METHOD

This was a 12-week open-label study of flexibly dosed milnacipran in patients (N = 5) experiencing chronic persistent knee pain ≥ 1 year following total knee arthroplasty in the absence of new injury, infection, or implant failure. Subjects were identified from October 2010 to August 2011 through the Duke University Medical Center orthopedic clinic (Durham, North Carolina), typically during 1-year postoperative follow-up visits, and were referred by their orthopedic surgeon.

RESULTS

Milnacipran treatment was associated with reduction in pain according to the primary outcome measure of the visual analog scale (VAS) score for pain (effect size of 1.15) and secondary outcome measures of Knee Society Score (KSS) evaluation subscale score (effect size of 1.37) and Medical Outcomes Study 36-item Short-Form Health Survey (SF-36) bodily pain subscale (effect size of 1.16) at week 12. Secondary outcome measures of functional change were mixed in such that, at week 12, the SF-36 physical functioning subscale showed improvement (effect size of 1.16), but the KSS function subscale score was just below the threshold for meaningful effect size (0.98).

CONCLUSIONS

Open-label milnacipran demonstrated reduced pain and some evidence of functional improvement in this small sample of patients with chronic persistent pain 1 year or more after total knee arthroplasty such that well-powered studies are warranted.

Current evidence on atypical odontalgia: diagnosis and clinical management

Patients with atypical odontalgia (AO) complain of medically unexplained toothache. No evidence-based diagnostic criteria or treatment guidelines are yet available. The present paper addresses seven clinical questions about AO based on current knowledge in the literature and discusses diagnostic criteria and guidelines for treatment and management. The questions are (i) What is the prevalence of AO in the community? (ii) What psychological problems are experienced by patients with AO? (iii) Are there any comorbidities of AO? (iv) Is local anesthesia effective for the relief of pain in AO? (v) Are there any characteristic symptoms of AO other than spontaneous pain? (vi) Are antidepressants effective for treatment of AO? (vii) Are anticonvulsants effective for treatment of AO? Our literature search provided answers for these questions; however, there is insufficient evidence-based data to establish guidelines for the diagnosis and treatment of AO. Overall, some diagnostic criteria for neuropathic pain and persistent dentoalveolar pain disorder may be applied to AO patients. The patient's psychogenic background should always be considered in the treatment and/or management of AO. The clinicians may need to treat AO patients using Patient-Oriented Evidence that Matters approach.

Plasma levels of milnacipran and its effectiveness for the treatment of chronic pain in the orofacial region

OBJECTIVES

This study was performed to assess the relationship between plasma levels of milnacipran and its analgesic/antidepressive effect in patients with chronic orofacial pain treated with this drug.

METHODS

A total of 44 patients took milnacipran for 12 weeks. Patients were assessed for their pain and depressive symptoms using the visual analog scale (VAS) and Hamilton Depression Rating Scale, respectively. The plasma milnacipran level was also assessed at week 12.

RESULTS

Forty patients completed study treatment and were included in the analysis. In these patients, the VAS score at week 12 significantly decreased from the baseline score (t = 5.15, p < 0.0001). The dose of milnacipran was positively correlated in a linear manner with the plasma level of the drug (Y = 44.86 + 0.33X, r = 0.54, R(2)  = 0.29, p = 0.0004). A quadratic regression curve was plotted between the percentage of decrease in the VAS score and plasma milnacipran level (Y = 27.39 + 0.76X - 0.008X(2) , p = 0.048, r = 0.40, R(2)  = 0.16). On the other hand, no significant relationship was noted between the percentage of decrease in the Hamilton Depression Rating Scale score and plasma milnacipran level.

CONCLUSION

The analgesic effect of milnacipran was suppressed in the presence of the plasma level of the drug outside the therapeutic range, whereas its antidepressant effect was not affected by its plasma level.

Literature mining for the discovery of hidden connections between drugs, genes and diseases

The scientific literature represents a rich source for retrieval of knowledge on associations between biomedical concepts such as genes, diseases and cellular processes. A commonly used method to establish relationships between biomedical concepts from literature is co-occurrence. Apart from its use in knowledge retrieval, the co-occurrence method is also well-suited to discover new, hidden relationships between biomedical concepts following a simple ABC-principle, in which A and C have no direct relationship, but are connected via shared B-intermediates. In this paper we describe CoPub Discovery, a tool that mines the literature for new relationships between biomedical concepts. Statistical analysis using ROC curves showed that CoPub Discovery performed well over a wide range of settings and keyword thesauri. We subsequently used CoPub Discovery to search for new relationships between genes, drugs, pathways and diseases. Several of the newly found relationships were validated using independent literature sources. In addition, new predicted relationships between compounds and cell proliferation were validated and confirmed experimentally in an in vitro cell proliferation assay. The results show that CoPub Discovery is able to identify novel associations between genes, drugs, pathways and diseases that have a high probability of being biologically valid. This makes CoPub Discovery a useful tool to unravel the mechanisms behind disease, to find novel drug targets, or to find novel applications for existing drugs.

The biomedical literature is an important source of knowledge on the function of genes and on the mechanisms by which these genes regulate cellular processes. Several text mining approaches have been developed to leverage this rich source of information by automatically extracting associations between concepts such as genes, diseases and drugs from a large body of text. Here, we describe a new method that extracts novel, not yet recognized associations between genes, diseases, drugs and cellular processes from the biomedical literature. Our method is built on the assumption that even if two concepts do not have a direct connection in literature, they may be functionally related if they are both connected to an overlapping set of concepts. Using this approach we predicted several novel connections between genes, diseases, drugs and pathways. Our results imply that our method is able to predict novel relationships from literature and, most importantly, that these newly identified relationships are biologically relevant. Our method can aid the drug discovery process where it can be used to find novel drug targets, increase insight in mode of action of a drug or find novel applications for known drugs.

Effectiveness of milnacipran for the treatment of chronic pain in the orofacial region

OBJECTIVES

The effect of milnacipran for the treatment of chronic pain in the orofacial region, including burning mouth syndrome (BMS) and atypical odontalgia (AO), was assessed while accounting for the influence of concurrent depressive symptoms on the pain-relieving effect.

METHODS

Milnacipran was administered for 12 weeks to 36 patients with chronic pain in the orofacial region (3 men and 29 women, aged between 22 and 76 years with a mean age of 59 years). Of those patients, 22 and 10 patients had BMS and AO, respectively. The initial dose of milnacipran was 15 mg a day, and the dose was raised up to 100 mg a day. Pain was assessed using the visual analog scale, and symptoms of depression were evaluated using the Hamilton Depression Rating Scale at baseline and at weeks 1, 2, 4, 6, 8, 10, and 12 of the study treatment.

RESULTS

Data from 32 patients who completed the study were included in the analysis. The visual analog scale score significantly decreased after the 12-week treatment, and it showed a similar time course of decline irrespective of concurrent depressive symptoms during the 12 weeks.

CONCLUSIONS

Treatment with milnacipran resulted in a significant improvement of chronic pain in the orofacial region irrespective of concurrent symptoms of depression. The present results suggested that milnacipran may be an effective agent for treatment of such disorders.

Efficacy of milnacipran in the treatment of chronic pain syndromes

Abstract Eleven outpatients with chronic pain syndromes other than fibromyalgia were treated for 12 weeks with milnacipran, a novel serotonin noradrenaline reuptake inhibitor. The agent was administered at 50-150 mg/day, and the mean ± SD dose at 12 weeks or at the time drug treatment was stopped was 84.1 ± 32.2 mg/day. None of the patients met the DSM-IV criteria for a major depressive disorder. Abdominal, chest, back, arm, leg or glossal pain, or headache was involved. Pain was assessed clinically by means of a visual analog scale (VAS) before and 12 weeks after the start of milnacipran treatment, or at the time drug treatment was stopped. The mean ± SD decrease in VAS scores was 42.3 ± 31.6 (50.8 ± 49.2%). One patient discontinued treatment after 4 weeks because of nausea, whereas others tolerated the agent well. These results suggest that the use of milnacipran in patients with a variety of chronic pain syndromes is beneficial.

The Efficacy and Safety of Milnacipran for Treatment of Fibromyalgia. A Randomized, Double-blind, Placebo-controlled Trial

Objective.

To evaluate the safety and efficacy of milnacipran, a dual norepinephrine and serotonin reuptake inhibitor, in the treatment of fibromyalgia (FM).

Methods.

A 27-week, randomized, double-blind, multicenter study compared milnacipran 100 and 200 mg/day with placebo in the treatment of 888 patients with FM. Two composite responder definitions were used to classify each patient’s individual response to therapy. “FM responders” concurrently satisfied response criteria for improvements in pain (visual analog scale 24-h morning recall), patient global impression of change (PGIC), and physical functioning (SF-36 Physical Component Summary); while “FM pain responders” concurrently satisfied response criteria for improvements in pain and PGIC.

Results.

At the primary endpoint, after 3-month stable dose treatment, a significantly higher percentage of milnacipran-treated patients met criteria as FM responders versus placebo (milnacipran 200 mg/day, p = 0.017; milnacipran 100 mg/day, p = 0.028). A significantly higher percentage of patients treated with milnacipran 200 mg/day also met criteria as FM pain responders versus placebo (p = 0.032). Significant pain reductions were observed after Week 1 with both milnacipran doses. At 15 weeks, milnacipran 200 mg/day led to significant improvements over placebo in pain (realtime, daily and weekly recall; all measures, p < 0.05), PGIC (p < 0.001), fatigue (p = 0.016), cognition (p = 0.025), and multiple SF-36 domains. Milnacipran was safe and well tolerated by the majority of patients during 27 weeks of treatment; nausea and headache were the most common adverse events.

Conclusion.

Milnacipran is safe and effective for the treatment of multiple symptoms of FM.

Japanese experience with milnacipran, the first serotonin and norepinephrine reuptake inhibitor in Japan

Milnacipran is a serotonin and norepinephrine reuptake inhibitor (SNRI), with a balanced potency for the inhibition of the reuptake of the two monoamines. In this, it contrasts with venlafaxine and duloxetine which, while possessing a dual action, have a selectivity of the order of 30-fold and 10-fold respectively for the reuptake of serotonin. Milnacipran has mainly been launched in countries where the selective serotonin reuptake inhibitors (SSRIs) and venlafaxine had been established for several years. As such it has attracted relative little interest from clinician investigators as a research tool. Japan, however, represents a unique situation because in 1999 milnacipran was launched within months of the first SSRI and is still the only SNRI in Japan together with only two SSRIs (a third has just been introduced). This has led to a large number of investigative clinical studies, many of which give interesting insights into the potential of milnacipran in the treatment of depression and of other disorders. This article reviews these Japanese studies with milnacipran.

Depression and pain: an overview

BACKGROUND

Depression and pain are both burdensome ailments that affect a major proportion of the population. It is evident that depression and pain frequently coexist, with treatment and outcome implications.

OBJECTIVE

To review the literature on the nature, prevalence and co-morbidity of depression and pain, the biological and psychological mechanisms involved and treatment options, thus presenting a broad overview of the current information available.

METHODS

Relevant sources were identified from PubMed and Medline databases using a combination of keywords including depression, pain, prevalence, co-morbidity, biological and psychological mechanisms, serotonin (5-HT), norepinephrine (NE), hypothalamic-pituitary-adrenal (HPA) axis, amygdala, functional magnetic resonance imaging (fMRI), antidepressant and psychological therapy.

RESULTS

It is evident from the research that depression and pain are common co-morbidities. Pain as a physical symptom of depression affects approximately 65% of patients, leading to less favourable outcomes and greater health care utilization. Moreover, depression is a common feature in chronic pain patients and can affect pain threshold and tolerance. Evidence from biological and psychological studies has revealed mechanisms that link chronic pain to depression. Several classes of anti-depressants and psychological interventions have been used successfully in the treatment of somatic symptoms of depression and for a variety of pain syndromes.

CONCLUSIONS

Pain and depression are linked by overlapping phenomenology, neurobiology and therapy. They are mutually interacting, and the interaction has significant treatment and outcome implications.