Efficacy of duloxetine in painful symptoms: an analgesic or antidepressant effect?

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Significant Analgesic Benefits of Perioperative Duloxetine in Patients Who Have Depressive Symptoms Undergoing Total Hip Arthroplasty: A Randomized Controlled Trial

BACKGROUND

Major symptoms of depression are commonly observed in patients requiring total hip arthroplasty (THA), and this is associated with increased pain scores and opioid consumption. We aimed to investigate the analgesic effect of duloxetine in these high-risk patients.

METHODS

Among 263 patients scheduled for primary unilateral THA, 67 patients who scored at least 8 on the 17-item Hamilton Depression Scale (HAMD) were enrolled in this study. Patients were randomized to the duloxetine group (60 mg daily, from the day of surgery to postoperative day 6) or the placebo group. The postoperative visual analog scale (VAS) score during walking, the VAS score during hip flexion, and resting VAS score was measured. Postoperative morphine consumption, hip range of motion (ROM), Harris hip score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function, postoperative length of stay (LOS), and adverse events were recorded.

RESULTS

The duloxetine group had significantly lower VAS scores during walking and hip flexion from postoperative day 3 to week 3 than the placebo group. With regard to the resting VAS score, duloxetine showed a better analgesic effect from postoperative day 3 to week 2 than placebo. Patients in the duloxetine group had less consumption of morphine. The duloxetine group exhibited better hip function scores, including ROM, HHS, and WOMAC function scores than the placebo group. No significant difference was observed in LOS or adverse events between groups.

CONCLUSION

Perioperative short-term duloxetine provides advantages in decreasing pain, reducing morphine consumption, and increasing hip function in THA patients who have depressive symptoms.

Activity dependent inhibition of TRPC1/4/5 channels by duloxetine involves voltage sensor-like domain

Transient receptor potential canonical 5 (TRPC5) is a polymodal, calcium-permeable, nonselective ion channel that is expressed in the brain and 75 % of human sensory neurons. Its pharmacological or genetic inhibition leads to the relief of neuropathic and inflammatory pain. The clinically approved drug duloxetine is superior to other serotonin and norepinephrine reuptake inhibitors at managing painful neuropathies, but it is not known why. Here we ask whether the TRPC5 receptor is modulated by duloxetine and may contribute to its analgesic effect. Electrophysiological measurements of heterologously expressed human TRPC5 in HEK293T cells were performed to evaluate the effect of duloxetine. The interaction site was identified by molecular docking and molecular dynamics simulations in combination with point mutagenesis. We found that duloxetine inhibits TRPC5 in a concentration-dependent manner with a high potency (IC₅₀ = 0.54 ± 0.03 µM). Our data suggest that duloxetine binds into a voltage sensor-like domain. For the interaction, Glu⁴¹⁸ exhibited particular importance due to putative hydrogen bond formation. Duloxetine effectively inhibits TRPC5 currents induced by cooling, voltage, direct agonists and by the stimulation of the PLC pathway. The finding that this TRPC5 inhibitor is widely used and well tolerated provides a scaffold for new pain treatment strategies.

Efficacy and safety of duloxetine in osteoarthritis or chronic low back pain: a Systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of duloxetine in the treatment of patients with osteoarthritis (OA) or chronic low back pain (CLBP).

METHODS

Relevant randomized controlled trials (RCTs) were searched in PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov. Included RCTs compared the efficacy and safety of duloxetine vs placebo in the treatment of OA or CLBP. Weighted mean difference (WMD) were calculated for continuous outcomes while risk ratio (RR) were calculated for dichotomous outcomes.

RESULTS

Nine RCTs were included in our meta-analysis. Duloxetine had significant improvement over placebo in Brief Pain Inventory 24-h average pain [WMD: -0.67; 95% confidence interval (CI):-0.80, -0.53], weekly mean of the 24-h average pain (WMD: -0.65; 95% CI: -0.79, -0.52), Patient's Global Impression of Improvement (WMD: -0.41; 95% CI: -0.49, -0.32), Clinical Global Impression of Severity (WMD: -0.32; 95% CI: -0.38, -0.25), European Quality of Life Questionnaire-5 Dimension (WMD: 0.04; 95% CI: 0.02, 0.07). In addition, duloxetine is associated with more treatment-emergent adverse events (TEAEs) (RR: 1.25; 95% CI: 1.17, 1.33) and discontinuations for adverse events (AEs) (RR: 2.31; 95% CI: 1.81, 2.94). However, there was no statistically significant difference in serious AEs between duloxetine and placebo.

CONCLUSION

Duloxetine had modest to moderate effects on pain relief, function improvement, mood regulation and improvement in quality of life with mild AEs in the treatment of OA or CLBP. Future RCTs should focus on comparing duloxetine with other oral drugs and assessing the long-term safety of duloxetine.

The Psychopharmacology Algorithm Project at the Harvard South Shore Program: An Update on Unipolar Nonpsychotic Depression

BACKGROUND

The Psychopharmacology Algorithm Project at the Harvard South Shore Program presents evidence-based recommendations considering efficacy, tolerability, safety, and cost. Two previous algorithms for unipolar nonpsychotic depression were published in 1993 and 1998. New studies over the last 20 years suggest that another update is needed.

METHODS

The references reviewed for the previous algorithms were reevaluated, and a new literature search was conducted to identify studies that would either support or alter the previous recommendations. Other guidelines and algorithms were consulted. We considered exceptions to the main algorithm, as for pregnant women and patients with anxious distress, mixed features, or common medical and psychiatric comorbidities.

SUMMARY

For inpatients with severe melancholic depression and acute safety concerns, electroconvulsive therapy (or ketamine if ECT refused or ineffective) may be the first-line treatment. In the absence of an urgent indication, we recommend trialing venlafaxine, mirtazapine, or a tricyclic antidepressant. These may be augmented if necessary with lithium or T3 (triiodothyronine). For inpatients with non-melancholic depression and most depressed outpatients, sertraline, escitalopram, and bupropion are reasonable first choices. If no response, the prescriber (in collaboration with the patient) has many choices for the second trial in this algorithm because there is no clear preference based on evidence, and there are many individual patient considerations to take into account. If no response to the second medication trial, the patient is considered to have a medication treatment-resistant depression. If the patient meets criteria for the atypical features specifier, a monoamine oxidase inhibitor could be considered. If not, reconsider (for the third trial) some of the same options suggested for the second trial. Some other choices can also considered at this stage. If the patient has comorbidities such as chronic pain, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, or posttraumatic stress disorder, the depression could be secondary; evidence-based treatments for those disorders would then be recommended.

Overlaps in pharmacology for the treatment of chronic pain and mental health disorders

There is significant overlap in the pharmacological management of pain and psychological disorders. Appropriate treatment of patients' comorbid psychological disorders, including sleep disturbances often leads to an improvement in reported pain intensity. The three first line agents for neuropathic pain include tricyclic antidepressants and serotonin norepinephrine reuptake inhibitors which are medications originally developed as antidepressants. The other first line medication for chronic neuropathic pain are anticonvulsant medications initially brought to the market-place for the treatment of epilepsy and are also now being used for the treatment of anxiety disorders and substance withdrawal symptoms. The efficacy of opioids for chronic pain is contentious, but it is agreed that the patients at highest risk for opioid misuse and addiction are patients with underlying psychological disorders who use opioids for their euphoric effects. Similarly, benzodiazepines may present a problem in patients with chronic pain, as up to one third of patients with pain are concomitantly prescribed benzodiazepines, and when combined with other sedating analgesic medications they put patients at increased risk for adverse events and polysubstance misuse. Finally, there is growing evidence for the efficacy of cannabis for treating neuropathic pain, but the consumption of cannabis has been associated with increased risk of psychosis in adolescents, and may be associated with an increased risk for developing bipolar disorder and anxiety disorders. The use of cannabis is associated with an increased risk of substance misuse in both adolescents and adults. In this narrative review, we examine the evidence for the use of several medications used for the treatment of both pain and psychological disorders, and their proposed mechanisms of action, in addition to special concerns for patients with comorbid pain and psychological disorders.

A Dual Noradrenergic Mechanism for the Relief of Neuropathic Allodynia by the Antidepressant Drugs Duloxetine and Amitriptyline

In addition to treating depression, antidepressant drugs are also a first-line treatment for neuropathic pain, which is pain secondary to lesion or pathology of the nervous system. Despite the widespread use of these drugs, the mechanism underlying their therapeutic action in this pain context remains partly elusive. The present study combined data collected in male and female mice from a model of neuropathic pain and data from the clinical setting to understand how antidepressant drugs act. We show two distinct mechanisms by which the selective inhibitor of serotonin and noradrenaline reuptake duloxetine and the tricyclic antidepressant amitriptyline relieve neuropathic allodynia. One of these mechanisms is acute, central, and requires descending noradrenergic inhibitory controls and α_2A adrenoceptors, as well as the mu and delta opioid receptors. The second mechanism is delayed, peripheral, and requires noradrenaline from peripheral sympathetic endings and β₂ adrenoceptors, as well as the delta opioid receptors. We then conducted a transcriptomic analysis in dorsal root ganglia, which suggested that the peripheral component of duloxetine action involves the inhibition of neuroimmune mechanisms accompanying nerve injury, including the downregulation of the TNF-α-NF-κB signaling pathway. Accordingly, immunotherapies against either TNF-α or Toll-like receptor 2 (TLR2) provided allodynia relief. We also compared duloxetine plasma levels in the animal model and in patients and we observed that patients' drug concentrations were compatible with those measured in animals under chronic treatment involving the peripheral mechanism. Our study highlights a peripheral neuroimmune component of antidepressant drugs that is relevant to their delayed therapeutic action against neuropathic pain.SIGNIFICANCE STATEMENT In addition to treating depression, antidepressant drugs are also a first-line treatment for neuropathic pain, which is pain secondary to lesion or pathology of the nervous system. However, the mechanism by which antidepressant drugs can relieve neuropathic pain remained in part elusive. Indeed, preclinical studies led to contradictions concerning the anatomical and molecular substrates of this action. In the present work, we overcame these apparent contradictions by highlighting the existence of two independent mechanisms. One is rapid and centrally mediated by descending controls from the brain to the spinal cord and the other is delayed, peripheral, and relies on the anti-neuroimmune action of chronic antidepressant treatment.

Regional brain functions in the resting state indicative of potential differences between depression and chronic pain

Complex relationships between depression and chronic pain have been reported in previous studies. However, only a few neuroimaging studies have investigated similarities and differences in neural systems underlying them. We examined the brain functions in the resting state of 43 patients with depression, 41 patients with chronic pain (somatoform pain disorder) and 41 healthy controls, by using regional homogeneity (ReHo) and functional connectivity analysis. Depressive symptoms were assessed by using the Beck Depression Inventory-Second Edition (BDI-II). ReHo values for the dorsolateral prefrontal cortex (DLPFC) significantly decreased for chronic pain patients, and functional connectivity between the DLPFC and thalamus decreased only for these patients. These findings are indicative of distinct brain functions related to depression and chronic pain. Understanding these differences would further elucidate the pathophysiology of these conditions.

Duloxetine Inhibits Microglial P2X4 Receptor Function and Alleviates Neuropathic Pain after Peripheral Nerve Injury

P2X4 receptors (P2X4R) are a family of ATP-gated non-selective cation channels. We previously demonstrated that activation of P2X4R in spinal microglia is crucial for neuropathic pain, a highly debilitating chronic pain condition, suggesting that P2X4R is a potential therapeutic target for treating neuropathic pain. Thus, the identification of a compound that has a potent inhibitory effect on P2X4R is an important clinical challenge. In the present study, we screened a chemical library of clinically approved drugs and show for the first time that duloxetine, a serotonin and noradrenaline reuptake inhibitor, has an inhibitory effect on rodent and human P2X4R. In primary cultured microglial cells, duloxetine also inhibited P2X4R-, but not P2X7R-, mediated responses. Moreover, intrathecal administration of duloxetine in a model of neuropathic pain produced a reversal of nerve injury-induced mechanical allodynia, a cardinal symptom of neuropathic pain. In rats that were pretreated with a serotonin-depleting agent and a noradrenaline neurotoxin, the antiallodynic effect of duloxetine was reduced, but still remained. Based on these results, we suggest that, in addition to duloxetine’s primary inhibitory action on serotonin and noradrenaline transporters, an inhibitory effect on P2X4R may be involved at least in part in an antiallodynic effect of intrathecal duloxetine in a model of neuropathic pain.

Influence of painful physical symptoms in the treatment of Japanese patients with melancholic major depressive disorder: A prospective cohort study

The aim of this study was to clarify how painful physical symptoms affect treatment outcomes in patients with melancholic major depressive disorder. The subjects comprised 100 consecutive Japanese outpatients with melancholic major depressive disorder who visited our clinic from October 2011 to October 2014. All subjects were interviewed for Diagnostic and Statistical Manual of Mental Disorders Axis 2, 3, and 4 and family history of major depressive disorder, and then grouped according to the presence of painful physical symptoms. We evaluated painful physical symptoms at baseline and after 12, 24, and 36 weeks of treatment and scores on the 17-item Hamilton Rating Scale for Depression, compared major depressive disorder remission between groups, and assessed responsiveness to antidepressants. The group with painful physical symptoms had a significantly more positive family history of major depressive disorder. The major depressive disorder remission rate was high in both groups, and no significant differences were observed. However, a significant relationship between major depressive disorder and painful physical symptoms remission was observed in the group with painful physical symptoms. A significantly higher number of remitted patients with painful physical symptoms (N=61) were administered serotonin-noradrenaline reuptake inhibitors, with significantly more receiving duloxetine than milnacipran.

Antidepressants and gabapentinoids in neuropathic pain: Mechanistic insights

Neuropathic pain arises as a consequence of a lesion or disease affecting the somatosensory system. It is generally chronic and challenging to treat. The recommended pharmacotherapy for neuropathic pain includes the use of some antidepressants, such as tricyclic antidepressants (TCAs) (amitriptyline…) or serotonin and noradrenaline re-uptake inhibitors (duloxetine…), and/or anticonvulsants such as the gabapentinoids gabapentin or pregabalin. Antidepressant drugs are not acute analgesics but require a chronic treatment to relieve neuropathic pain, which suggests the recruitment of secondary downstream mechanisms as well as long-term molecular and neuronal plasticity. Noradrenaline is a major actor for the action of antidepressant drugs in a neuropathic pain context. Mechanistic hypotheses have implied the recruitment of noradrenergic descending pathways as well as the peripheral recruitment of noradrenaline from sympathetic fibers sprouting into dorsal root ganglia; and importance of both α2 and β2 adrenoceptors have been reported. These monoamine re-uptake inhibitors may also indirectly act as anti-proinflammatory cytokine drugs; and their therapeutic action requires the opioid system, particularly the mu (MOP) and/or delta (DOP) opioid receptors. Gabapentinoids, which target the voltage-dependent calcium channels α2δ-1 subunit, inhibit calcium currents, thus decreasing the excitatory transmitter release and spinal sensitization. Gabapentinoids also activate the descending noradrenergic pain inhibitory system coupled to spinal α2 adrenoceptors. Gabapentinoid treatment may also indirectly impact on neuroimmune actors, like proinflammatory cytokines. These drugs are effective against neuropathic pain both with acute administration at high dose and with repeated administration. This review focuses on mechanistic knowledge concerning chronic antidepressant treatment and gabapentinoid treatment in a neuropathic pain context.

Correlation between pain response and improvements in patient-reported outcomes and health-related quality of life in duloxetine-treated patients with diabetic peripheral neuropathic pain

OBJECTIVE

We assessed whether quality of life (QoL) improvement in duloxetine-treated patients with diabetic peripheral neuropathic pain (DPNP) correlates with the extent of pain relief.

METHODS

Pooled data from three multicountry, double-blind, 12-week, placebo-controlled trials of duloxetine-treated (duloxetine 60 mg once daily; total number =335) patients with DPNP were analyzed. Based on improvement in 24-hour average pain scores, patients were stratified into four groups. Improvement in QoL, which was measured as the change from baseline in two patient-reported health outcome measures (Short Form [SF]-36 and five-dimension version of the EuroQol Questionnaire [EQ-5D]), was evaluated and compared among the four groups. Pearson's correlation coefficient was calculated to assess the correlation between improvement in pain scores and improvement in QoL.

RESULTS

The group with more pain improvement generally showed greater mean change from baseline in all of the SF-36 scale scores and on the EQ-5D index. Pearson's correlation coefficients ranged from 0.114 to 0.401 for the SF-36 scale scores (P<0.05), and it was 0.271 for the EQ-5D (P<0.001).

CONCLUSION

Improvement in pain scores was positively correlated with improvement in QoL and patient-reported outcomes in duloxetine-treated patients.

A selective α2 B adrenoceptor agonist (A-1262543) and duloxetine modulate nociceptive neurones in the medial prefrontal cortex, but not in the spinal cord of neuropathic rats

BACKGROUND

The noradrenergic system contributes to pain modulation, but the roles of its specific adrenoceptors are still being defined. We have identified a novel, potent (rat EC50  = 4.3 nM) and selective α2B receptor agonist, A-1262543, to further explore this adrenoceptor subtype's contribution to pathological nociception.

METHODS

Systemic administration of A-1262543 (1-10 mg/kg, intraperitoneal) dose-dependently attenuated mechanical allodynia in animals with a spinal nerve ligation injury. To further explore its mechanism of action, the activity of nociceptive neurones in the spinal cord and medial prefrontal cortex (mPFC) were examined after injection of 3 mg/kg of A-1262543 (intravenous, i.v.). These effects were compared with duloxetine (3 mg/kg, i.v.), a dual noradrenaline (NA) and serotonin (5-HT) reuptake inhibitor.

RESULTS

Systemic administration of A-1262543 or duloxetine did not alter the spontaneous or evoked firing of spinal wide dynamic range and nociceptive-specific neurones in the neuropathic rats, indicating that neither compound engaged spinal, peripheral or descending pathways. In contrast to the lack of effect on spinal neurones, both A-1262543 and duloxetine reduced the evoked and spontaneous firing of 'pain-responsive' (PR) neurones in the mPFC. Duloxetine, but not A-1262543, also inhibited the firing of pain non-responsive (nPR) neurones in the mPFC probably reflecting duloxetine's contribution to modulating non-pain endpoints.

CONCLUSIONS

These data highlight that activation of the α2B adrenoceptor as well as inhibiting NA and 5-HT reuptake can result in modulating the ascending nociceptive system, and in particular, dampening the firing of PR neurones in the mPFC.

Does pain interfere with antidepressant depression treatment response and remission in patients with depression and pain? An evidence-based structured review

OBJECTIVE

The objective of this evidence-based structured review was to determine if there is consistent evidence that pain interferes with achieving antidepressant treatment response/remission of depression in patients with depression and pain.

METHODS

After exclusion criteria were applied, of 2,801 studies/reports, 17 studies addressed this question. They were sorted into the four hypotheses outlined herein after. The percentage of studies supporting/not supporting each hypothesis was calculated. The strength and consistency of the evidence for each hypothesis were rated according to the Agency for Health Care Research and Quality (AHRQ) guidelines.

RESULTS

For the first hypothesis (pretreatment pain levels will predict antidepressant depression response), nine out of 10 (90%) studies supported it. For the second hypothesis (treatment decreases in pain will be associated with antidepressant depression response), two out of two (100%) studies supported it. For the third hypothesis (pretreatment pain levels will predict antidepressant depression remission), six out of six (100%) studies supported it. For the fourth hypothesis (treatment decreases in pain will be associated with antidepressant depression remission), five out of five (100%) supported it. Utilizing these percentages and AHRQ guidelines, hypotheses 1, 3, and 4 received an A rating for consistency of studies in supporting them. A consistency rating for hypothesis 2 could not be generated because of too few studies in that group.

CONCLUSIONS

Consistent evidence was found that antidepressant treatment of depression in patients with depression and pain can be negatively impacted by pain for achieving depression response/remission. However, the overall number of studies supporting each hypothesis was small. In addition, several potential confounders of the results of this study were identified.

Rapid Management of Trigeminal Neuralgia and Comorbid Major Depressive Disorder With Duloxetine

Objective: To describe a case of a patient diagnosed with major depressive disorder whose trigeminal neuralgia was unexpectedly but rapidly and efficiently responsive to duloxetine. Case Summary: A 37-year-old woman was diagnosed with trigeminal neuralgia, and the initial treatment with carbamazepine 800 mg/d did not improve her pain. In the following 3 years, she was poorly responsive to the combination therapy with several medications, including carbamazepine, valproate, baclofen, diclofenac, and acetaminophen. The repeated gamma knife radiosurgery still did not relieve her symptoms. She developed clinically significant depressive symptoms, and a diagnosis of major depressive disorder was made. Duloxetine 30 mg/d was initiated for the management of depression, with the dose gradually increased to 60 mg/d. Unexpectedly, at the dose of 60 mg/d, the patient reported remarkable relief in her trigeminal neuralgia within the first week. Her depressed mood gradually improved in the following 3 weeks. At the 4-year follow-up, she was gradually tapered off her medications, and her depression and trigeminal neuralgia were well managed on duloxetine 60 mg/d and carbamazepine 600 mg/d. Discussion: The mechanisms may be related to duloxetine’s ability to modulate norepinephrine and serotonin and antagonize N-methyl-d-aspartate (NMDA) receptors. The ignition hypothesis is a proposed etiology of trigeminal neuralgia, in that any individual hyperexcitable neuron can spread its discharge quickly to activate the entire population of neurons. We suggest that duloxetine exerts desynchronizing effects through its NMDA antagonism, modulating the hyperexcitable state of the trigeminal afferents. Conclusions: Duloxetine may be an adjuvant in treatment-resistant trigeminal neuralgia.

Duloxetine for treating painful neuropathy, chronic pain or fibromyalgia

BACKGROUND

Duloxetine is a balanced serotonin and noradrenaline reuptake inhibitor licensed for the treatment of major depressive disorders, urinary stress incontinence and the management of neuropathic pain associated with diabetic peripheral neuropathy. A number of trials have been conducted to investigate the use of duloxetine in neuropathic and nociceptive painful conditions. This is the first update of a review first published in 2010.

OBJECTIVES

To assess the benefits and harms of duloxetine for treating painful neuropathy and different types of chronic pain.

SEARCH METHODS

On 19th November 2013, we searched The Cochrane Neuromuscular Group Specialized Register, CENTRAL, DARE, HTA, NHSEED, MEDLINE, and EMBASE. We searched ClinicalTrials.gov for ongoing trials in April 2013. We also searched the reference lists of identified publications for trials of duloxetine for the treatment of painful peripheral neuropathy or chronic pain.

SELECTION CRITERIA

We selected all randomised or quasi-randomised trials of any formulation of duloxetine, used for the treatment of painful peripheral neuropathy or chronic pain in adults.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We identified 18 trials, which included 6407 participants. We found 12 of these studies in the literature search for this update. Eight studies included a total of 2728 participants with painful diabetic neuropathy and six studies involved 2249 participants with fibromyalgia. Three studies included participants with depression and painful physical symptoms and one included participants with central neuropathic pain. Studies were mostly at low risk of bias, although significant drop outs, imputation methods and almost every study being performed or sponsored by the drug manufacturer add to the risk of bias in some domains. Duloxetine at 60 mg daily is effective in treating painful diabetic peripheral neuropathy in the short term, with a risk ratio (RR) for ≥ 50% pain reduction at 12 weeks of 1.73 (95% CI 1.44 to 2.08). The related NNTB is 5 (95% CI 4 to 7). Duloxetine at 60 mg daily is also effective for fibromyalgia over 12 weeks (RR for ≥ 50% reduction in pain 1.57, 95% CI 1.20 to 2.06; NNTB 8, 95% CI 4 to 21) and over 28 weeks (RR 1.58, 95% CI 1.10 to 2.27) as well as for painful physical symptoms in depression (RR 1.37, 95% CI 1.19 to 1.59; NNTB 8, 95% CI 5 to 14). There was no effect on central neuropathic pain in a single, small, high quality trial. In all conditions, adverse events were common in both treatment and placebo arms but more common in the treatment arm, with a dose-dependent effect. Most adverse effects were minor, but 16% of participants stopped the drug due to adverse effects. Serious adverse events were rare.

AUTHORS' CONCLUSIONS

There is adequate amounts of moderate quality evidence from eight studies performed by the manufacturers of duloxetine that doses of 60 mg and 120 mg daily are efficacious for treating pain in diabetic peripheral neuropathy but lower daily doses are not. Further trials are not required. In fibromyalgia, there is lower quality evidence that duloxetine is effective at similar doses to those used in diabetic peripheral neuropathy and with a similar magnitude of effect. The effect in fibromyalgia may be achieved through a greater improvement in mental symptoms than in somatic physical pain. There is low to moderate quality evidence that pain relief is also achieved in pain associated with depressive symptoms, but the NNTB of 8 in fibromyalgia and depression is not an indication of substantial efficacy. More trials (preferably independent investigator led studies) in these indications are required to reach an optimal information size to make convincing determinations of efficacy.Minor side effects are common and more common with duloxetine 60 mg and particularly with 120 mg daily, than 20 mg daily, but serious side effects are rare.Improved direct comparisons of duloxetine with other antidepressants and with other drugs, such as pregabalin, that have already been shown to be efficacious in neuropathic pain would be appropriate. Unbiased economic comparisons would further help decision making, but no high quality study includes economic data.

Impaired noradrenaline homeostasis in rats with painful diabetic neuropathy as a target of duloxetine analgesia

BACKGROUND

Painful diabetic neuropathy (PDN) is a serious complication of diabetes mellitus that affects a large number of patients in many countries. The molecular mechanisms underlying the exaggerated nociception in PDN have not been established. Recently, duloxetine (DLX), a serotonin and noradrenaline re-uptake inhibitor, has been recommended as one of the first-line treatments of PDN in the United States Food and Drug Administration, the European Medicines Agency and the Japanese Guideline for the Pharmacologic Management of Neuropathic pain. Because selective serotonin re-uptake inhibitors show limited analgesic effects in PDN, we examined whether the potent analgesic effect of DLX contributes toward improving the pathologically aberrant noradrenaline homeostasis in diabetic models.

RESULTS

In streptozotocin (STZ) (50 mg/kg, i.v.)-induced diabetic rats that exhibited robust mechanical allodynia and thermal hyperalgesia, DLX (10 mg/kg, i.p.) significantly and markedly increased the nociceptive threshold. The analgesic effect of DLX was nullified by the prior administration of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) (50 mg/kg, i.p.), which drastically eliminated dopamine-beta-hydroxylase- and norepinephrine transporter-immunopositive fibers in the lumbar spinal dorsal horn and significantly reduced the noradrenaline content in the lumbar spinal cord. The treatment with DSP-4 alone markedly lowered the nociceptive threshold in vehicle-treated non-diabetic rats; however, this pro-nociceptive effect was occluded in STZ-treated diabetic rats. Furthermore, STZ-treated rats exhibited a higher amount of dopamine-beta-hydroxylase- and norepinephrine transporter-immunopositive fibers in the dorsal horn and noradrenaline content in the spinal cord compared to vehicle-treated rats.

CONCLUSIONS

Impaired noradrenaline-mediated regulation of the spinal nociceptive network might underlie exaggerated nociception in PDN. DLX might exert its analgesic effect by selective enhancement of noradrenergic signals, thus counteracting this situation.

Duloxetine in panic disorder with somatic gastric pain

PANIC DISORDER IS THE MOST COMMON TYPE OF ANXIETY DISORDER, AND ITS MOST COMMON EXPRESSION IS PANIC ATTACKS CHARACTERIZED WITH SUDDEN ATTACKS OF ANXIETY WITH NUMEROUS SYMPTOMS, INCLUDING PALPITATIONS, TACHYCARDIA, TACHYPNEA, NAUSEA, AND VERTIGO: ie, cardiovascular, gastroenterologic, respiratory, and neuro-otologic symptoms. In clinical practice, panic disorder manifests with isolated gastroenteric or cardiovascular symptoms, requiring additional clinical visits after psychiatric intervention. The first-line treatment for anxiety disorders, and in particular for panic disorder, is the selective serotonin reuptake inhibitors. However, these drugs can have adverse effects, including sexual dysfunction, increased bodyweight, and abnormal bleeding, that may be problematic for some patients. Here we report the case of a 29-year-old Caucasian woman affected by panic disorder with agoraphobia who was referred to our clinic for recurrent gastroenteric panic symptoms. The patient reported improvement in her anxiety symptoms and panic attacks while on a selective serotonin reuptake inhibitor, but not in her gastric somatic problems, so the decision was taken to start her on duloxetine, a serotonin-norepinephrine reuptake inhibitor. After 6 months of treatment, the patient achieved complete remission of her gastric and panic-related symptoms, and was able to stop triple gastric therapy. Other authors have hypothesized and confirmed that duloxetine has greater initial noradrenergic effects than venlafaxine and is effective in patients with panic disorder. This case report underscores the possibility of tailoring therapeutic strategies for the gastroenteric expression of panic disorder.

Fibromyalgia syndrome: etiology, pathogenesis, diagnosis, and treatment

Fibromyalgia syndrome is mainly characterized by pain, fatigue, and sleep disruption. The etiology of fibromyalgia is still unclear: if central sensitization is considered to be the main mechanism involved, then many other factors, genetic, immunological, and hormonal, may play an important role. The diagnosis is typically clinical (there are no laboratory abnormalities) and the physician must concentrate on pain and on its features. Additional symptoms (e.g., Raynaud's phenomenon, irritable bowel disease, and heat and cold intolerance) can be associated with this condition. A careful differential diagnosis is mandatory: fibromyalgia is not a diagnosis of exclusion. Since 1990, diagnosis has been principally based on the two major diagnostic criteria defined by the ACR. Recently, new criteria have been proposed. The main goals of the treatment are to alleviate pain, increase restorative sleep, and improve physical function. A multidisciplinary approach is optimal. While most nonsteroidal anti-inflammatory drugs and opioids have limited benefit, an important role is played by antidepressants and neuromodulating antiepileptics: currently duloxetine (NNT for a 30% pain reduction 7.2), milnacipran (NNT 19), and pregabalin (NNT 8.6) are the only drugs approved by the US Food and Drug Administration for the treatment of fibromyalgia. In addition, nonpharmacological treatments should be associated with drug therapy.

Efficacy of duloxetine on painful physical symptoms in major depressive disorder for patients with clinically significant painful physical symptoms at baseline: a meta-analysis of 11 double-blind, placebo-controlled clinical trials

OBJECTIVE

To review efficacy of duloxetine for physical symptoms and depressive illness in patients with at least mild to moderate major depressive disorder (MDD; DSM-IV) and clinically significant painful physical symptoms at baseline.

DATA SOURCES

Global database of duloxetine clinical trials (Eli Lilly and Company).

STUDY SELECTION

All 11 acute, double-blind, placebo-controlled studies of duloxetine (7 with duloxetine 60-mg doses and 4 with non-60-mg doses) in the database that used a scale to measure painful physical symptoms and were completed before March 17, 2011.

DATA EXTRACTION

For each study, patients with clinically significant pain levels at baseline (Visual Analog Scale overall pain rating ≥ 30, Numerical Rating Scale score ≥ 3, or Brief Pain Inventory 24-hour average pain rating ≥ 3) were selected in order to determine the effect sizes of duloxetine (compared with placebo for each trial) on the pain and depression measures. Overall effect sizes for both painful physical symptoms and MDD were obtained from the mean of individual-trial effect sizes, and each effect size was weighted relative to the number of patients within each study.

DATA SYNTHESIS

The overall mean effect sizes were as follows: painful physical symptoms-60-mg trials, 0.29 (95% CI, 0.06 to 0.52); non-60-mg trials, 0.13 (95% CI, -0.19 to 0.45); MDD-60-mg trials, 0.29 (95% CI, 0.18 to 0.40); non-60-mg trials, 0.16 (95% CI, 0.00 to 0.32). Across the 11 studies, the weighted effect size for painful physical symptoms was 0.26 (95% CI, 0.00 to 0.51) and for MDD, 0.25 (95% CI, 0.16 to 0.34).

CONCLUSIONS

According to this meta-analysis, duloxetine 60 mg once daily is as effective in improving painful physical symptoms as it is for depression in patients with MDD and clinically significant painful physical symptoms. The results of this meta-analysis indicate that duloxetine has small effect sizes in reducing painful physical symptoms and depressive symptoms in patients with MDD and clinically significant pain levels at baseline. Thus, the results of the study permit one to conclude that duloxetine has a clinically significant impact on painful physical symptoms and in reducing the severity of depressive symptoms. However, the results do not address its efficacy compared to other alternatives, as in all studies the comparator was placebo.

Review of Efficacy and Safety of Duloxetine 40 to 60 mg Once Daily in Patients with Diabetic Peripheral Neuropathic Pain

We summarize efficacy and safety findings from 4 double-blind, placebo-controlled, 12-week studies and 1 open-label, uncontrolled, 34-week maintenance-of-effect (MOE) study that examine duloxetine 40 and 60 mg once daily (QD) in patients with diabetic peripheral neuropathic pain (DPNP). In all placebo-controlled studies, duloxetine showed significantly (P ≤ .01) greater reduction in pain severity (weekly mean of 24-hour average pain severity ratings, primary outcome measure) compared with placebo. In all placebo-controlled studies, duloxetine showed significantly (P ≤ .05) greater improvement on brief pain inventory-Interference ratings. Patient global impression of improvement ratings were superior to placebo (P ≤ .01) for duloxetine patients in all placebo-controlled studies. Response rates (based on 30% pain reduction) ranged from 57% to 68% for duloxetine and from 35% to 47% for placebo and were statistically significantly different (P ≤ .01) between treatment groups in 3 out of 4 studies. The open-label study showed maintenance of analgesic effect of duloxetine in DPNP. In the duloxetine groups, 4.3% to 14.9% of patients discontinued because of adverse events (placebo groups: 2.6% to 7.4%). Most commonly reported treatment-emergent adverse events were nausea, somnolence, and headache. Duloxetine 40 and 60 mg QD was efficacious and well tolerated in the management of DPNP.

Implications of pain in generalized anxiety disorder: efficacy of duloxetine

OBJECTIVE

To conduct a post hoc evaluation of the prevalence of clinically significant pain and the efficacy of duloxetine in patients with generalized anxiety disorder (GAD) and concurrent pain.

METHOD

Data from two 9- to 10-week double-blind, placebo-controlled, randomized clinical trials of duloxetine (60 to 120 mg) in DSM-IV-defined GAD were analyzed (study 1 was conducted from July 2004 to September 2005; study 2 was conducted from August 2004 to June 2005). Efficacy was assessed with the Hamilton Rating Scale for Anxiety (HAM-A), visual analog scales (VAS) for pain, the Hospital Anxiety Depression Scale (HADS), the Clinical Global Impressions-Improvement of Illness (CGI-I) scale, the Patient Global Impressions-Improvement (PGI-I) scale, and the Sheehan Disability Scale (SDS) global functional impairment scale.

RESULTS

Of 840 patients randomly assigned to treatment, 61.3% (302 duloxetine, 213 placebo) had VAS scores ≥ 30 mm on at least 1 of the pain scales, indicating clinically significant pain. Among those patients with concurrent pain at baseline, change from baseline to endpoint in the HAM-A total score (42.9% change in mean scores for duloxetine, 31.4% for placebo), HADS anxiety scale (40.3% vs. 22.8%), HADS depression scale (36.1% vs. 20.5%), HAM-A psychic factor (45.9% vs. 29.9%), and SDS global functional improvement score (45.5% vs. 22.1%) was significantly (all p's < .001) greater for duloxetine compared with placebo. Improvement on the CGI-I (p = .003) and PGI-I (p < .001) was also significantly greater for duloxetine. Response (HAM-A total score decrease ≥ 50%) (49% vs. 29%) and remission (HAM-A total score ≤ 7 at endpoint) (29% vs. 18%) rates were significantly greater for duloxetine compared with placebo (p < .001 and p = .041, respectively). Duloxetine demonstrated statistically significantly greater reduction in pain on all 6 VAS pain scales (all p's < .001 except headaches with p < .002) (for duloxetine, percent change in means from baseline to endpoint ranged from 40.1% to 45.2% across the 6 VAS scales; for placebo, 22.0% to 26.3%).

CONCLUSION

Duloxetine, relative to placebo, improves anxiety symptoms, pain, and functional impairment among patients with GAD with concurrent clinically significant pain.

TRIAL REGISTRATION

clinicaltrials.gov Identifiers: NCT00122824 (study 1) and NCT00475969 (study 2).

Tolerability aspects in duloxetine-treated patients with depression: Should one use a lower starting dose in clinical practice?

OBJECTIVE

This study questions whether a lower starting dose of duloxetine (DLX) could be beneficial for patients with depression, in terms of tolerability and safety in routine clinical care.

RESEARCH DESIGN AND METHODS

Post-hoc analyses of a multicenter, prospective, non-interventional, 6-month study in adult outpatients with a depressive episode was undertaken.

MAIN OUTCOME MEASURES

Treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), discontinuations due to TEAEs and hospitalizations due to depression, were all documented at 2 weeks, 4 weeks, 3 months and 6 months after treatment initiation/switch to DLX.

RESULTS

Of 4517 patients enrolled, 4313 were included for TEAE evaluation. TEAEs occurred in 17.2% of patients, and SAEs occurred in 0.79% of patients, including one case of suicidal ideation. 1404 patients discontinued within 6 months (TEAEs: n = 119). Starting treatment with 30 mg/day DLX (72.7%) was favored in females, or after inadequate efficacy of previous antidepressant treatment; 60 mg/day DLX was favored in more severe depression and patients receiving concomitant pain medication.

CONCLUSION

Initiating treatment with 60 mg/day DLX was not associated with poorer tolerability in this study. Physicians may be guided by their clinical experience to carefully consider the individual benefit/risk ratio and TEAE susceptibility when deciding to start treatment with a higher or a lower dose of DLX.

Time course of improvement of different symptom clusters in patients with major depression and pain treated with duloxetine or placebo

OBJECTIVE

This post hoc analysis assessed improvements in a broad range of psychopathological dimensions and in interference of pain with functioning as well as the time course of these improvements in patients with major depressive disorder (MDD) and pain treated with duloxetine versus placebo.

RESEARCH DESIGN AND METHODS

Data were derived from an 8-week, double-blind, placebo-controlled study in adult outpatients with MDD and non-specific physical pain. Mean times between improvement in Brief Pain Inventory (BPI) pain severity and interference of pain with functioning, depression severity, and dimensions of the Symptom Checklist-90 Revised (SCL-90-R) subscales were evaluated by responder analysis.

RESULTS

For all SCL-90-R subscores, a higher percentage of duloxetine-treated patients reached responder status (50% improvement) as compared to placebo, of these anger/hostility and interpersonal sensitivity had the highest response rates. In the duloxetine-treated group, response for anger/hostility, phobic anxiety, psychoticism, and most items assessing interference of pain with functioning was reached earlier than response for pain severity. The times to response for Montgomery-Asberg Depression Rating Scale (MADRS) and for pain severity were similar. In the placebo-treated group, times to response for depression, anxiety, and MADRS were longer than response for pain severity.

CONCLUSIONS

Duloxetine, and to a lesser degree placebo, not only improved depressive symptomatology and pain severity but also a much broader range of psychopathological symptoms. Time courses of improvements were different for duloxetine and placebo, in that depression and interference of pain with functioning improved earlier than pain severity in duloxetine-treated patients but not in placebo-treated patients. These results suggest that time to response is a valuable means of characterizing treatment effects.

LIMITATIONS

Pain was only assessed as a symptom and no further clinical diagnosis for pain syndromes were performed. CLINICAL TRIAL REGISTRY ID: www.clinicaltrial.gov - NCT00191919.

A spinal mechanism of action for duloxetine in a rat model of painful diabetic neuropathy

BACKGROUND AND PURPOSE

This study was designed to clarify mechanisms responsible for the anti-allodynic effects of duloxetine in diabetes.

EXPERIMENTAL APPROACH

The streptozotocin-induced diabetic rat model was used to compare the efficacy of duloxetine, 5-HT, the 5-HT(2A) receptor agonist [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI)] and two antagonists (ketanserin and pruvanserin) on tactile allodynia.

KEY RESULTS

Systemic or intrathecal injection of duloxetine alleviated tactile allodynia in diabetic rats. The effect of systemic duloxetine was reduced by intrathecal administration of ketanserin or pruvanserin, indicating participation of spinal 5-HT(2A) receptors in the mechanism of action of duloxetine. In contrast to spinal delivery, systemic and local peripheral injections of ketanserin or pruvanserin alleviated tactile allodynia in diabetic rats. This effect was reversed immediately after systemic or local DOI injection.

CONCLUSIONS AND IMPLICATIONS

These results support the involvement of spinal 5-HT(2A) receptors in the ability of duloxetine to ameliorate painful diabetic neuropathy. Our data also suggest that the role of 5-HT(2A) receptors depends on the level of the neuraxis at which activation takes place, with peripheral activation contributing to tactile allodynia in diabetic rats, whereas spinal activation of this receptor alleviates tactile allodynia. The development of selective peripheral 5-HT(2A) receptor antagonists may offer a novel approach for the treatment of diabetic neuropathic pain.

Estimation of minimum clinically important difference for pain in fibromyalgia

OBJECTIVE

To estimate the minimum clinically important difference (MCID) for several pain measures obtained from the Brief Pain Inventory (BPI) for patients with fibromyalgia.

METHODS

Data were pooled across 12-week treatment periods from 4 randomized, double-blind, placebo-controlled studies designed to evaluate the safety and efficacy of duloxetine for the treatment of fibromyalgia. Each study enrolled subjects with American College of Rheumatology--defined fibromyalgia who presented with moderate to severe pain. The MCIDs for the BPI average pain item score and the BPI severity score (the mean of the BPI pain scale values: right now, average, least, and worst) were estimated by anchoring against the Patient's Global Impressions of Improvement scale.

RESULTS

The anchor-based MCIDs for the BPI average pain item and severity scores were 2.1 and 2.2 points, respectively. These MCIDs correspond to 32.3% and 34.2% reductions from baseline in scores.

CONCLUSION

In these analyses, the MCIDs for several pain measures obtained from the BPI were similar (∼2 points) and corresponded to a 30-35% improvement from baseline to end point. These findings may be beneficial for use in designing clinical trials in which the BPI is used to evaluate improvements in pain severity.

Treatment adherence and persistence with duloxetine, venlafaxine XR, and escitalopram among patients with major depressive disorder and chronic pain-related diseases

OBJECTIVE

Chronic pain is prevalent in patients with major depressive disorder (MDD). This study compared adherence and persistence rates among MDD patients with comorbid chronic pain-related diseases (CPD, including fibromyalgia, diabetes with neurological manifestations, osteoarthritis, low back pain, and headache) for three antidepressants: duloxetine, venlafaxine XR, and escitalopram.

RESEARCH DESIGN AND METHODS

A retrospective analysis was conducted of 15,523 adult MDD patients with CPD in the MarketScan Commercial Claims and Encounters Database who started on one of the study medications between 07/01/06 and 06/30/07. Patients were followed-up for 6 months. Adherence was reported using a medication possession ratio ≥0.8. Persistence was measured using persistence rates (proportions of patients who continuously refilled prescriptions during 6 months) and duration of therapy (number of days patients remained on the study medication before a prescription gap over 30 days). Multivariate logistic regression on adherence and persistence rates and linear regression on duration of therapy adjusting for patient and prescription characteristics were conducted.

RESULTS

Patients on duloxetine had a higher adherence rate (46.03%) than those on venlafaxine XR (42.94%; p = 0.0033) or escitalopram (37.27%; p < 0.0001). Patients on duloxetine also had a higher persistence rate and longer duration of therapy (43.66%, 117.82 days) than did patients treated with venlafaxine XR (40.38%; p = 0.0017; 114.24 days; p = 0.009) or escitalopram (33.86%; p < 0.0001; 105.73 days; p < 0.0001). These differences were still significant after adjusting for patient and prescription characteristics (p < 0.05). Sensitivity analyses found similar patterns using an allowable gap for refill of 15 days.

CONCLUSIONS

Among commercially insured MDD patients with CPD, duloxetine-treated patients had higher adherence and persistence rates than did patients treated with venlafaxine XR or escitalopram during 6 months after medication initiation. Future studies should examine the clinical and economic implications of these differences.

LIMITATIONS

This study has limitations such as possible selection bias using secondary database analysis.

Duloxetine for the treatment of mood disorder in cancer patients: a 12-week case-control clinical trial

OBJECTIVE

The aim of this study was to investigate the efficacy and tolerability of duloxetine in cancer patients with mood disorder (MD) by means of a comparison with a matched control group of patients with MD without medical illness.

METHODS

Fifty-nine consecutive patients with MD were enrolled in this prospective case-control study and received duloxetine 60/120 mg per day for 12 weeks. Twenty-seven patients were affected by cancer, whereas 32 had an MD without cancer. All the patients were assessed by means of efficacy and effectiveness tolerability scales for depression (Montgomery-Asberg Depression Rating Scale and Hospital Anxiety and Depression Scale), anxiety (State-Trait Anxiety Inventory-Y1/Y2) and severity of symptoms (Clinical Global Impression (CGI)-Severity) at baseline (T0), after 4 weeks (T1) and 12 weeks (T2). The CGI-Improvement, CGI-Effectiveness Index and Dosage Record Treatment Emergent Symptom Scale were administered at T1 and T2.

RESULTS

A significant global improvement in all the efficacy measures was found. The results showed no significant interaction 'Time X Group', suggesting a similar improvement in efficacy scores for cancer-depressed patients and depressed patients without cancer. No difference was found between the two groups with regard to drop-out percentage, effectiveness and tolerability.

CONCLUSION

Although the results of this case-control study are preliminary, they suggest that duloxetine can be considered a good option for the treatment of MD in cancer patients.

A double-blind, randomized, placebo-controlled study of the efficacy and safety of duloxetine for the treatment of chronic pain due to osteoarthritis of the knee

OBJECTIVE

To evaluate the efficacy and safety of duloxetine in the treatment of chronic pain due to osteoarthritis of the knee.

METHODS

This was a 13-week, randomized, double-blind, placebo-controlled trial in patients meeting American College of Rheumatology clinical and radiographic criteria for osteoarthritis of the knee. At baseline, patients were required to have a ≥ 4 weekly mean of the 24-hour average pain ratings. Patients were randomized to either duloxetine 60 mg once daily (QD) or placebo. At week 7, the duloxetine dosage was increased, in a blinded fashion, to 120-mg QD in patients reporting < 30% pain reduction. The primary efficacy measure was Brief Pain Inventory (BPI) 24-hour average pain. Secondary efficacy measures included Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); Clinical Global Impressions of Severity (CGI-S). Safety and tolerability was also assessed.

RESULTS

Of the total (n = 256) patients, 111 (86.7%) in placebo group and 93 (72.7%) in duloxetine group completed the study. Patients treated with duloxetine had significantly (P ≤ 0.001) greater improvement at all time points on BPI average pain and had significantly greater improvement on BPI pain severity ratings (P ≤ 0.05), WOMAC total (P = 0.044) and physical functioning scores (P = 0.016), and CGI-S (P = 0.009) at the study endpoint. Frequency of treatment-emergent nausea, constipation, and hyperhidrosis were significantly higher in the duloxetine group (P ≤ 0.05). Significantly more duloxetine-treated patients discontinued the trial because of adverse events (P = 0.002).

CONCLUSIONS

Treatment with duloxetine 60 mg to 120 mg QD was associated with significant pain reduction and improved function in patients with pain due to osteoarthritis of the knee.

Attributes of response in depressed patients switched to treatment with duloxetine

BACKGROUND

This study was designed to assess clinical and functional outcomes associated with switching to duloxetine treatment in patients with major depressive disorder (MDD) experiencing emotional and painful physical symptoms in their current episode.

METHODS

In this 8-week, multinational, multicentre, single-arm, open-label clinical trial, 242 MDD patients were switched to duloxetine 60 mg/day after selective serotonin reuptake inhibitor (SSRI) or serotonin and norepinephrine reuptake inhibitor (SNRI) treatment. The primary analysis compared mean change from baseline in Brief Pain Inventory-Modified Short Form (BPI-SF) interference score between initial responders [≥ 50% reduction from baseline on the 17-item Hamilton Depression Rating Scale (HAMD(17)) Maier subscale] and initial non-responders after 4 weeks. Initial responders continued with duloxetine 60 mg/day. Initial non-responders received duloxetine 120 mg/day for the remaining 4 weeks. Depression, pain, anxiety and functional outcomes were also compared after 8 weeks.

RESULTS

BPI-SF interference decreased from baseline in initial responders (n = 108) and initial non-responders (n = 85) after 4 weeks of duloxetine treatment, with greater reductions in initial responders [BPI-SF mean difference in reduction: 1.01 (95% CI 0.42-1.61); p < 0.001]. Reductions in pain interference favouring initial responders were also apparent after 8 weeks [0.68 (95% CI: 0.03-1.33); p = 0.042]. Depression, pain, anxiety and function improved over 8 weeks across patient groups.

CONCLUSIONS

Elements of core mood and pain are important residual symptoms following poor treatment response in MDD. Early improvement in these symptoms after switching to duloxetine indicated an increased chance of functional recovery.

Fibromyalgia: diagnosis and treatment options

BACKGROUND

Fibromyalgia is a widespread, chronic pain disorder that includes a complex constellation of somatic and emotional symptoms. Controlled clinical trials for both medication and nonmedication therapies have led to sound, evidence-based recommendations for the care of patients with fibromyalgia.

OBJECTIVE

This review article was designed to provide updated information from database literature searches on fibromyalgia epidemiology, including gender differences, psychological comorbidity, and treatment with medication and nonmedication therapies.

METHODS

A literature review was performed by identifying fibromyalgia articles published in English from January 2000 to October 2008 using the PubMed and EMBASE databases. Search terms included fibromyalgia, exercise, gender, nonpharmacologic, placebo-controlled, randomized, and treatment.

RESULTS

New epidemiologic data support important differences in fibromyalgia symptom severity between the sexes and the important role of comorbid psychological distress. Physicians diagnose fibromyalgia in women at an approximately 3- to 6-fold rate compared with men. Well-conducted clinical trials and recently published treatment guidelines reinforce effective treatment with medication and nonpharmacologic therapy. The strongest evidence suggests effective treatment of fibromyalgia with duloxetine and milnacipran. Studies also report efficacy with gabapentin, pramipexole, pregabalin, tramadol, and IV tropisetron. Nonpharmacologic treatments should include fitness and strengthening exercise, as well as warm-water therapy and psychological pain management techniques.

CONCLUSIONS

Fibromyalgia is a common, disabling, chronic pain condition that predominantly affects women. Symptoms can be effectively treated using both drug and nondrug therapies. In general, treatment benefits in fibromyalgia appear largely independent of patient sex.

Duloxetine for the treatment of fibromyalgia

This article presents a brief review of the physiologic abnormalities seen in fibromyalgia, current theories of widespread pain, and treatment options, including emerging therapeutics, with a focus on the use of duloxetine to manage fibromyalgia symptoms. Major clinical trials that examine the efficacy and effectiveness of duloxetine to date are reviewed, and safety issues are discussed.

Use of benzodiazepines, hypnotics, and anxiolytics in major depressive disorder: association with chronic pain diseases

We examined the use of benzodiazepines (BZD), hypnotics, and anxiolytics and their associations with chronic pain diseases (CPD) in patients with major depressive disorder (MDD). A retrospective analysis of 153,913 MDD patients (18-64 years) in a large administrative insured claims database during the year 2006 was performed. Results showed that during the study year, 33.1% of the patients had been prescribed BZD; 16.9%, hypnotics; and 6.1%, anxiolytics. The use of BZD and hypnotics increased with age. Patients with CPD were more likely than those without CPD to use BZD (41.2% vs. 27.0%, p < 0.001), hypnotics (21.7% vs. 13.3%, p < 0.001), and anxiolytics (7.8% vs. 4.8%, p < 0.01). After adjustment for demographics and comorbidities, CPD was still significantly associated with increased use of BZD (OR = 1.62), hypnotics (OR = 1.49), and anxiolytics (OR = 1.51). Further research is needed to examine the long-term benefits and risks of BZD and hypnotics in the treatment of MDD and CPD.

Use of duloxetine in patients with an anxiety disorder, or with comorbid anxiety and major depressive disorder: a review of the literature

IMPORTANCE OF THE FIELD

Except for generalized anxiety disorder, few reports have been published on the efficacy, safety and tolerability of duloxetine in patients with anxiety disorders individually or in comorbidity with major depressive disorder (MDD).

AREAS COVERED IN THIS REVIEW

The literature search in Medline (dating back to 1966) and Embase (dating back to 1988) databases was conducted using the OVID interface on 9 April 2009, restricted to any article or abstract in English, per title, reporting any information on the use of duloxetine in patients with any anxiety disorder with or without concomitant MDD. A systematic review approach was taken.

WHAT THE READER WILL GAIN

The reader will gain knowledge of the current data available on the use of duloxetine to treat patients with anxiety disorders individually or in comorbidity with MDD.

TAKE HOME MESSAGE

Duloxetine could be considered an effective treatment option in the treatment of anxiety disorders individually or in comorbidity with each other, or with MDD; however, apart from the well-demonstrated efficacy, tolerability and safety of duloxetine in the treatment of MDD with or without anxiety and GAD, data on this subject are preliminary and very limited, and more research is warranted.

Comparative pain and mood effects in patients with comorbid fibromyalgia and major depressive disorder: secondary analyses of four pooled randomized controlled trials of duloxetine

The objective of this paper is to better understand the relationship of pain and mood in patients with fibromyalgia and comorbid major depressive disorder (MDD). Pooled data from 4 double-blind, placebo-controlled, randomized trials of duloxetine hydrochloride 60-120mg/day in patients with fibromyalgia were included (N=1332). Of these, 350 (26% [147 placebo, 203 duloxetine]) had comorbid MDD (per Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision criteria) and were included in these analyses. Primary measures included Brief Pain Inventory average pain; Hamilton Depression Rating Scale or Beck Depression Inventory. Logistic regression was used to evaluate the consistency of treatment effect across various subgroups. Path analysis was used to assess the effect of duloxetine on improvement in pain in the presence of improvement in mood and vice versa. Results indicated that 69% of improvement in pain was a direct effect of treatment, with improvement in mood accounting for 31% of pain response. In conclusion, consistent with our hypothesis, duloxetine produced a substantial direct effect on pain improvement and change in mood exerted a modest indirect effect on pain improvements in patients with fibromyalgia and MDD. Hence, both direct and indirect analgesic and antidepressant properties appear to be relevant for the treatment of these comorbid patients with duloxetine.

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>or=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; Patient's 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 Patient's 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.

Pharmacologic management of chronic pain

Chronic pain is a multifactorial condition with both physical and psychological symptoms, and it affects around 20% of the population in the developed world. In spite of outstanding advances in pain management over the past decades, chronic pain remains a significant problem. This article provides a mechanism- and evidence-based approach to improve the outcome for pharmacologic management of chronic pain. The usual approach to treat mild to moderate pain is to start with a nonopioid analgesic. If this is inadequate, and if there is an element of sleep deprivation, then it is reasonable to add an antidepressant with analgesic qualities. If there is a component of neuropathic pain or fibromyalgia, then a trial with one of the gabapentinoids is appropriate. If these steps are inadequate, then an opioid analgesic may be added. For moderate to severe pain, one would initiate an earlier trial of a long term opioid. Skeletal muscle relaxants and topicals may also be appropriate as single agents or in combination. Meanwhile, the steps of pharmacologic treatments for neuropathic pain include (1) certain antidepressants (tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors), calcium channel α₂-δ ligands (gabapentin and pregabalin) and topical lidocaine, (2) opioid analgesics and tramadol (for first-line use in selected clinical circumstances) and (3) certain other antidepressant and antiepileptic medications (topical capsaicin, mexiletine, and N-methyl-d-aspartate receptor antagonists). It is essential to have a thorough understanding about the different pain mechanisms of chronic pain and evidence-based multi-mechanistic treatment. It is also essential to increase the individualization of treatment.

Milnacipran: beyond a role of antidepressant

Milnacipran is a serotonin and norepinephrine reuptake inhibitor (SNRI) with negligible effects on any presynaptic or postsynaptic receptors. Milnacipran has unique pharmacokinetic and pharmacodynamic characteristics that distinguish it from the other marketed serotonin and norepinephrine reuptake inhibitors, venlafaxine, desvenlafaxine, and duloxetine such as equipotent serotonin and norepinephrine reuptake inhibition and a linear dose-concentration trend at therapeutic doses. The half-life of milnacipran is approximately 8 hours. In addition, milnacipran does not inhibit the cytochrome P 450 system, indicating minimal propensity for drug-drug interactions. The antidepressant efficacy of milnacipran has been clearly established in a number of randomized, double-blind, placebo-controlled clinical trials, and it has been widely used for treating major depressive disorder. Moreover, evidence suggests that milnacipran is effective and tolerable in the treatment of fibromyalgia and may have usefulness for fatigue and anxiety symptoms. The current paper reviews researches conducted to date that is relevant to the efficacy, tolerability, and mechanism of action of milnacipran in the treatment of depression, fibromyalgia, and other psychiatric syndromes. Future directions of research are also identified.

Pain associated with specific anxiety and depressive disorders in a nationally representative population sample

OBJECTIVE

To examine in a nationally representative sample (a) the differential association of specific anxiety and depressive disorders defined according to DSM-IV with pain disorder (PD) and pain symptoms, and (b) whether pain-associated anxiety and depressive disorders and their comorbidity have different implications in terms of impairment, disability, health care utilization, and substance use.

METHOD

A nationally representative community study was conducted in Germany. Symptoms, syndromes and diagnoses of mental disorders, and pain were assessed in N = 4,181 participants aged 18-65 years using the DSM-IV/M-CIDI.

RESULTS

Logistic regressions revealed that pain is associated with both specific anxiety and depressive disorders, with increasing significant odds ratios (OR) for medically explained pain symptoms (EPS; OR range: 1.9-2.0), to unexplained pain symptoms (UPS; OR range: 2.4-7.3), to PD (OR range: 3.3-14.8). PD and UPS persistently showed associations after adjusting for comorbid other anxiety and depressive disorders and physical illnesses. All types of pain, particularly PD/UPS, are associated with decreased quality of life, greater impairment in role functioning, disability, health care utilization, and substance use. Depressive disorders, even more so anxiety disorders and their comorbidity account for a substantial proportion of variance in these functional correlates.

CONCLUSIONS

Pain is strongly associated with specific anxiety and depressive disorders. In light of the individual and societal burden due to pain, and the demonstrated role of comorbid anxiety or/and depression, our results call for further investigation of the underlying mechanisms for this association as well as targeted treatments for these comorbidities.

Duloxetine for treating painful neuropathy or chronic pain

BACKGROUND

Duloxetine is a balanced serotonin and noradrenaline reuptake inhibitor licensed for the treatment of major depressive disorders, urinary stress incontinence and the management of neuropathic pain associated with diabetic peripheral neuropathy. A number of trials have been conducted to investigate the use of duloxetine in neuropathic and nociceptive painful conditions.

OBJECTIVES

To assess the benefits and harms of duloxetine for treating painful neuropathy and different types of chronic pain.

SEARCH STRATEGY

We searched The Cochrane Neuromuscular Group Specialized Register (10 March 2009), The Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2009), MEDLINE (January 1966 to March 2009), EMBASE (January 1980 to March 2009), and www.clinicaltrials.gov to March 2009 and the reference lists of identified publications for trials of duloxetine used for the treatment of painful peripheral neuropathy or chronic pain.

SELECTION CRITERIA

We selected all randomised or quasi-randomised trials of any formulation of duloxetine, used for the treatment of painful peripheral neuropathy or chronic pain in adult participants.

DATA COLLECTION AND ANALYSIS

Two authors extracted data independently onto a specially designed proforma and cross checked them.

MAIN RESULTS

Six trials were identified including 2220 participants. Three studies included participants with painful diabetic neuropathy and three treated participants with fibromyalgia. Duloxetine at 60 mg daily is effective in treating painful diabetic peripheral neuropathy in the short-term to 12 weeks with a risk ratio (RR) for 50% pain reduction at 12 weeks of 1.65 (95% confidence interval (CI) 1.34 to 2.03), number needed to treat (NNT) 6 (95% CI 5 to 10). Duloxetine at 60 mg daily is also effective in fibromyalgia over 12 weeks (RR 50% reduction in pain 1.57, 95% CI 1.20 to 2.06; NNT 8, 95% CI 5 to 17) and 28 weeks (RR 1.58, 95% CI 1.10 to 2.27). Adverse events were common in both treatment and placebo arms but more common in the treatment arm with a dose dependent effect. Most side effects were minor, but 16% of participants stopped the drug due to side effects. Serious adverse events were rare.

AUTHORS' CONCLUSIONS

There is moderately strong evidence that duloxetine 60 mg and 120 mg daily are efficacious for treating pain in diabetic peripheral neuropathy and fibromyalgia but 20 mg daily is not. Minor side effects are common at therapeutic doses but serious side effects are rare. Direct comparisons of duloxetine with other antidepressants and with other drugs already shown to be efficacious in neuropathic pain would be appropriate and should include unbiased economic analyses.

Psychiatric issues in chronic pain

Chronic pain requires comprehensive care. While interdisciplinary approaches are recommended, the role of psychiatrists is often misunderstood. Psychiatrists should be involved with the care of patients with chronic pain as early as possible to maximize outcome. Psychiatrists offer an expertise that specifically addresses important deficiencies in the care of patients with chronic pain: 1) the lack of a detailed formulation, 2) the lumping of all psychopathology, and 3) the failure to effectively use psychopharmacologic treatments. This review provides a framework for formulating the diagnoses and treatments of patients with chronic pain.

Pharmacotherapy of chronic pain: a synthesis of recommendations from systematic reviews

OBJECTIVES

Chronic pain is one of the most prevalent, costly and disabling conditions in both clinical practice and the workplace, yet often remains inadequately treated. Moreover, chronic pain commonly co-occurs with depression, anxiety and somatoform disorders, and adversely affects response of these conditions to psychiatric treatments. This article provides an evidence-based approach to the pharmacotherapy of chronic pain.

METHODS

This narrative review is derived largely from meta-analyses and systematic reviews published since 2005. For a few medications, findings from multiple recent trials are synthesized if a systematic review had not yet been published. Classes of medications are first reviewed, followed by an overview of four common pain disorders: neuropathic pain, low back pain, fibromyalgia and osteoarthritis.

RESULTS

A stepped care approach based upon existing evidence includes (1) simple analgesics (acetaminophen or nonsteroidal anti-inflammatory drugs); (2) tricyclic antidepressants (if neuropathic, back or fibromyalgia pain) or tramadol; (3) gabapentin, duloxetine or pregabalin if neuropathic pain; (4) cyclobenzaprine, pregabalin, duloxetine, or milnacipran for fibromyalgia; (5) topical analgesics (capsaicin, lidocaine, salicylates) if localized neuropathic or arthritic pain; and (6) opioids. Disease-specific recommendations for neuropathic, low back, fibromyalgia and osteoarthritis pain are reviewed.

CONCLUSIONS

A number of medications have proven effective in chronic pain disorders and their use individually or in combination should improve the management of chronic pain.

Switching to duloxetine in selective serotonin reuptake inhibitor non- and partial-responders: effects on painful physical symptoms of depression

Painful physical symptoms (PPS) are common in patients with depression. Our objective was to evaluate the presence of PPS in a sample of SSRI non- or partial-responders with MDD and examine the effect of a switch to duloxetine on those PPS. Outpatients who met criteria for MDD despite having taken an SSRI antidepressant for at least 6 weeks, and who had a Hamilton depression rating scale total score of at least 15 and a clinical global impression of severity score of at least 3, were randomized to switch to duloxetine by either a direct switch or a start-taper switch method. PPS were assessed at baseline and at the study endpoint using various measures including six visual analog scales (VAS) for pain (overall pain, headache, back pain, shoulder pain, interference with daily activities, and time in pain while awake), the pain subscale of the symptom questionnaire-somatic subscale, and the bodily pain subscale of the short form-36 item health survey. Clinically significant levels of pain (mean baseline VAS scores >30 mm) were seen across all VAS pain measures prior to switching. Switch to duloxetine was associated with significant improvements on all pain measures regardless of switch method, and there was evidence for an earlier reduction in pain in the start-taper switch group. In summary, MDD patients who were non- or partial-responders to SSRI treatment were found to have clinically significant pain which improved significantly following switch to duloxetine regardless of the switch method utilized.

The relationship between fibromyalgia and major depressive disorder: a comprehensive review

OBJECTIVE

A large body of evidence suggests that the relationship between major depressive disorder (MDD) and fibromyalgia (FM) is complex. Improved understanding of this relationship promises to provide clinicians with better assessment and treatment options for both disorders.

METHOD

This paper reviews research on the prevalence, etiology and pathogenesis, clinical characterization, and treatment of FM and MDD, as well as studies that examined the relationship between these disorders. Studies were identified via PubMed literature search.

RESULTS

Our findings point to substantial similarities in neuroendocrine abnormalities, psychological characteristics, physical symptoms and treatments between FM and MDD. However, currently available findings do not support the assumption that MDD and FM refer to the same underlying construct or can be seen as subsidiaries of one disease concept.

CONCLUSION

New methodological and theoretical approaches may lead to a better understanding of the link between FM and MDD, and to more effective psychological and psychopharmacological therapies for FM patients. In the meantime, clinicians should carefully screen for a history of MDD in patients with FM.

Duloxetine: a review of its use in the treatment of major depressive disorder

Duloxetine (Cymbalta) is an orally administered, selective serotonin and noradrenaline reuptake inhibitor (SNRI) that has been approved for the treatment of major depressive disorder (MDD). Based on a considerable body of evidence, duloxetine at dosages ranging from 40 to 120 mg/day was effective in the short- and long-term treatment of MDD. Significant improvements versus placebo in core emotional symptoms as well as painful physical symptoms associated with depression, were seen in most, but not all, appropriately designed studies; results of meta-analyses suggested that improvements in these efficacy measures were apparent after 1-2 weeks' treatment with the highest recommended dosage of 60 mg once daily. Short-term (< or =15 weeks) administration of duloxetine at fixed or flexible dosages between 60 and 120 mg/day was noninferior to paroxetine 20 mg once daily, noninferior or inferior to escitalopram 10-20mg once daily, and had a similar global benefit-risk (GBR) profile to that of venlafaxine extended-release (XR) 150-225 mg/day in the treatment of MDD. Longer-term (6-8 months) treatment with duloxetine was similar in efficacy to paroxetine and escitalopram. Duloxetine is generally well tolerated, although it may be appropriate to avoid initiating treatment with the 60 mg/day dosage, as this has been associated with a higher discontinuation rate due to adverse events in some (but not all) comparative studies with escitalopram and venlafaxine XR. Definitive comparisons are awaited, although duloxetine seemingly provides a useful alternative to SSRIs and other SNRIs for the treatment of MDD. It also appears to be an attractive option for MDD patients presenting with painful physical symptoms.