Safety of tapentadol compared with other opioids in chronic pain treatment: network meta-analysis of randomized controlled and withdrawal trials.

OBJECTIVE: To assess the relative safety of oral tapentadol PR and other opioid analgesics for moderate or severe chronic pain in adults, we conducted a systematic review and network meta-analysis (NMA). METHODS: A systematic review was conducted to identify randomized controlled trials (RCTs) and randomized withdrawal trials of tapentadol with other WHO stage II and III opioid analgesics in patients with moderate or severe chronic pain. Searches were conducted in MEDLINE, EMBASE, PubMed, Cochrane databases and trial registries. Feasibility assessment evaluated the trials' suitability for NMA. Outcomes assessed were overall AEs, overall serious adverse events, constipation, nausea, dizziness, somnolence, headache, and discontinuation due to AEs. Randomized withdrawal trials were analyzed separately to other RCTs. RESULTS: Searches conducted in April 2019 identified 16,604 records. Following screening and feasibility assessment, 29 RCTs and 19 randomized withdrawal trials were identified and included in the NMA. Consistent with existing research, evidence from RCTs suggested that tapentadol is associated with relatively lower odds of adverse events occurring than most active comparators. The withdrawal trial data were less clear, with higher uncertainty around the results, and results that appear to contradict the RCT evidence. There are a number of trial design factors that may be affecting these results. CONCLUSIONS: RCT evidence suggests that tapentadol can be a useful treatment option for patients suffering from chronic pain and in need of an opioid analgesic. Opioids should be prescribed by a qualified physician only after other analgesics have been considered, taking side effects and misuse risk into account.

painPREDICT: first interim data from the development of a new patient-reported pain questionnaire to predict treatment response using sensory symptom profiles.

Objective: Sensory symptom patterns may be useful for predicting treatment response, and, thus, improve individual therapy in patients suffering from neuropathic pain (NeP). Existing screening questionnaires focus predominately on neuropathic mechanisms without consideration of nociceptive mechanisms or mixed pain states. This study aimed to develop a new questionnaire, painPREDICT, using a wide set of patient-reported descriptors potentially associated with neuropathic and nociceptive pain mechanisms, and to explore sensory symptom patterns. Methods: PainPREDICT was constructed based on exploratory (n = 27 patients) and cognitive debriefing interviews (n = 49 patients and nine physicians), across five NeP conditions. The pilot questionnaire was then administered in a non-interventional, cross-sectional, multi-center study to 840 pain patients across the US and Germany. The identification of a sensory symptom pattern was based on hybrid clustering resulting from items standardization followed by principal component analysis. Results: The final questionnaire included 20 items covering: pain intensity, location of pain, course of pain, and sensory symptoms. Most patients participating in the cross-sectional study suffered either from painful diabetic polyneuropathy (n = 330) or radiculopathy (n = 349), fewer from central pain (n = 61) or other types of NeP (n = 100). The hybrid clustering of the new questionnaire data identified three different characteristic sensory symptom profiles in patients with NeP: "Irritable nociceptors", "deafferentation pain", and "pain attacks with nociceptive component". Although some differences in the distribution of the sensory profiles were found, all profiles were represented in all NeP etiology groups. Conclusions: This study set the ground of painPREDICT and showed promising results for its use to categorize patients according to sensory symptom patterns.

Neuropathic pain in cancer: systematic review, performance of screening tools and analysis of symptom profiles.

BACKGROUND: The objectives of this study were to evaluate the methodological quality of rigorous neuropathic pain assessment tools in applicable clinical studies, and determine the performance of screening tools for identifying neuropathic pain in patients with cancer. METHODS: Systematic literature search identified studies reporting use of Leeds Assessment of Neuropathic Symptoms and Signs (LANSS), Douleur Neuropathique en 4 (DN4) or painDETECT (PDQ) in cancer patients with a clinical diagnosis of neuropathic or not neuropathic pain. Individual patient data were requested to examine descriptor item profiles. RESULTS: Six studies recruited a total of 2301 cancer patients of which 1564 (68%) reported pain. Overall accuracy of screening tools ranged from 73 to 94%. There was variation in description and rigour of clinical assessment, particularly related to the rigour of clinical judgement of pain as the reference standard. Individual data from 1351 patients showed large variation in the selection of neuropathic pain descriptor items by cancer patients with neuropathic pain. LANSS and DN4 items characterized a significantly different neuropathic pain symptom profile from non-neuropathic pain in both tumour- and treatment-related cancer pain aetiologies. CONCLUSIONS: We identified concordance between the clinician diagnosis and screening tool outcomes for LANSS, DN4 and PDQ in patients with cancer pain. Shortcomings in relation to standardized clinician assessment are likely to account for variation in screening tool sensitivity, which should include the use of the neuropathic pain grading system. Further research is needed to standardize and improve clinical assessment in patients with cancer pain. Until the standardization of clinical diagnosis for neuropathic cancer pain has been validated, screening tools offer a practical approach to identify potential cases of neuropathic cancer pain.

Treatment of painful radiculopathies with capsaicin 8% cutaneous patch.

BACKGROUND AND OBJECTIVE: The treatment of neuropathic pain due to low-back (lumbosacral) radiculopathies, a common source of neuropathic pain, is challenging and often requires a multimodal therapeutic approach. The capsaicin 8% patch is the first topical analgesic licensed for peripheral neuropathic pain. To evaluate this treatment, a subset of patients with painful radiculopathy (lumbar and cervical, including ventral and dorsal rami) enrolled into the multicenter, non-interventional QUEPP study (Qutenza 2 - safety and effectiveness in peripheral neuropathic pain) was analyzed. METHODS: Of the 1044 study participants, 50 were diagnosed with painful radiculopathy as only peripheral neuropathic pain syndrome and were eligible for evaluation. Patients received a single treatment (visit 1) with follow-up visits 2-5 at weeks 1-2, 4, 8 and 12. Parameters assessed at all visits included pain intensity, neuropathy symptoms and side effects. Quality of life (SF-12) and painDETECT 1 questionnaires were completed at baseline and final visit. Data was analyzed by patch application site and duration of pain. RESULTS: Topical treatment led to a significant decrease of pain intensity between weeks 1/2 and week 12 versus baseline at the application sites representing dermatomes of ventral (N = 26) and dorsal rami (N = 13) of spinal nerves. A significant decline (p ≤ .001) of numeric pain rating scale scores was observed between weeks 1/2 following patch application and the end of observation (week 12) in the overall radiculopathy group (N = 50), and the groups with either 3 months to 2 years (N = 14) or >2 years (N = 23) duration of pain. Pain relief of at least 30% was observed in 50.0%, 71.4% and 39.1% of patients in the respective groups. Four patients experienced in total seven adverse drug reactions (application site pain or pruritus). CONCLUSION: Effective neuropathic pain relief was observed after patch application within the innervation territories of both dorsal and ventral branches of the spinal nerve. Further controlled randomized trials are indicated.

Emergent biomarker derived from next-generation sequencing to identify pain patients requiring uncommonly high opioid doses.

Next-generation sequencing (NGS) provides unrestricted access to the genome, but it produces 'big data' exceeding in amount and complexity the classical analytical approaches. We introduce a bioinformatics-based classifying biomarker that uses emergent properties in genetics to separate pain patients requiring extremely high opioid doses from controls. Following precisely calculated selection of the 34 most informative markers in the OPRM1, OPRK1, OPRD1 and SIGMAR1 genes, pattern of genotypes belonging to either patient group could be derived using a k-nearest neighbor (kNN) classifier that provided a diagnostic accuracy of 80.6±4%. This outperformed alternative classifiers such as reportedly functional opioid receptor gene variants or complex biomarkers obtained via multiple regression or decision tree analysis. The accumulation of several genetic variants with only minor functional influences may result in a qualitative consequence affecting complex phenotypes, pointing at emergent properties in genetics.

A retrospective analysis of the long-term test-retest stability of pain descriptors of the painDETECT questionnaire.

OBJECTIVE: PainDETECT (PD-Q) is a patient reported screening questionnaire to identify patients with neuropathic pain based on questions regarding typically sensory symptoms of neuropathic pain. The aim of the present investigation was to assess the test-retest stability of pain descriptors of the PD-Q within a time window of 1-3 weeks. METHODS: Data sets of 74 chronic pain patients sampled in an open pain register at two visits were analyzed and compared. Patients with change of pain localization between visits were excluded from analysis. Beside conventional measures (Pearson correlation coefficient r, intraclass correlation coefficient ICC, kappa), also calculated measures known from method comparison were used. RESULTS: The mean duration between visits was 15 days. The measures were in the range of r = 0.72-0.86, ICC = 0.71-0.86, and kappa = 0.62-0.72 for PD-Q pain descriptors (burning, prickling, mechanical allodynia, pain attacks, thermal hyperalgesia, numbness, pressure induced pain). CONCLUSION: The individual PD-Q pain descriptors showed accurate test-retest stability as a prerequisite for use in repeated measurements (e. g. post baseline or follow up data) in clinical trials.

Are there different predictors of analgesic response between antidepressants and anticonvulsants in painful diabetic neuropathy?

BACKGROUND: To investigate baseline demographics and disease characteristics as predictors of the analgesic effect of duloxetine and pregabalin on diabetic peripheral neuropathic pain (DPNP). METHODS: Based on data from the COMBO-DN study, a multinational clinical trial in DPNP, the potential impact of baseline characteristics on pain relief after 8-week monotherapy with 60 mg/day duloxetine or 300 mg/day pregabalin was assessed using analyses of covariance. Subgroups of interest were characterized regarding their baseline characteristics and efficacy outcomes. RESULTS: A total of 804 patients were evaluated at baseline. A significant interaction with treatment was observed in the mood symptom subgroups with a larger pain reduction in duloxetine-treated patients having no mood symptoms [Hospital Anxiety and Depression Scale (HADS) depression or anxiety subscale score <11; -2.33 (duloxetine); -1.52 (pregabalin); p = 0.024]. There were no significant interactions between treatment for subgroups by age (<65 or ≥65 years), gender, baseline pain severity [Brief Pain Inventory Modified Short Form (BPI-MSF) average pain <6 or ≥6], diabetic neuropathy duration (≤2 or >2 years), baseline haemoglobin A1c (HbA1c) (<8% or ≥8%), presence of comorbidities and concomitant medication use. CONCLUSIONS: Our analyses suggest that the efficacy of duloxetine and pregabalin for initial 8-week treatment in DPNP was consistent across examined subgroups based on demographics and disease characteristics at baseline except for the presence of mood symptoms. Duloxetine treatment appeared to be particularly beneficial in DPNP patients having no mood symptoms.

Mechanism- and experience-based strategies to optimize treatment response to the capsaicin 8% cutaneous patch in patients with localized neuropathic pain.

The capsaicin 8% cutaneous patch is an emergent new treatment option for patients with peripheral neuropathic pain. In randomized controlled clinical studies relevant pain relief for 12 weeks was achieved in about one third of patients following a single application. The first part of this paper is a review of the pathophysiology, pharmacology, and published clinical trials with the capsaicin 8% cutaneous patch. The second part reports on outcomes of an interdisciplinary expert workshop, where new treatment results of three major German pain centers were presented and reviewed with the objectives of obtaining responder rates for different pain syndromes, assessing maintenance of effect under real-life conditions, and giving recommendations for practical care. The 12 week responder rates with pain relief of ≥ 30% were comparable in patients with mononeuropathies (37.9%) and postherpetic neuralgia (38.8%). Similar responder rates were seen in a subgroup of patients with cervical spine radiculopathy and back pain (46.7%). In HIV-associated neuropathy the responder rates were high (47.8%) but lower in patients with other polyneuropathies (17.6%). Response rates were nearly identical after 1 week (46.6%) and 4 weeks (43.3) and dropped only slightly at 12 weeks (37.4%). In a subgroup of 54 patients who underwent a second treatment, efficacy was maintained. Response rates in patients with or without lidocaine pretreatment were comparable. Treatment with the capsaicin 8% cutaneous patch was generally safe and well tolerated. The workshop panel recommended further investigation of opportunities to improve the application procedure and to perform studies on the skin penetration and distribution of capsaicin. A modified quantitative sensory testing (QST) should be developed for clinical practice in order to better understand the correlation of sensory profiles and response to capsaicin treatment.

Efficacy and safety of pregabalin in treatment refractory patients with various neuropathic pain entities in clinical routine.

AIMS: Conventional approaches to the management of neuropathic pain (NeP) often yield unsatisfactory results. We aimed to investigate pregabalin, a gamma-aminobutyric acid (GABA)-analogue, in a wide range of pregabalin naive patients with treatment refractory NeP. METHODS: Investigator-initiated, 4-week, open, prospective multicentre study in tertiary care. Pregabalin was prescribed at physicians' discretion based on patients' individual responses and tolerability, with or without concomitant analgesics. Consecutive patients were requested to fill in questionnaires at baseline and after 14 and 28 days with numerical pain rating scales (0, none; 10, worst possible), sleep rating scales, parts of the Brief Pain Inventory, Pain Experience Scale, Short Questionnaire on Current Burden and the SF-12 health-related quality of life scale. RESULTS: In 55 patients, the mean pregabalin dose was 142 +/- 26 mg at day 1 and 348 +/- 161 mg at day 28. The mean pain score decreased from 6.5 +/- 1.7 to 5.5 +/- 1.9 at day 14 and to 4.9 +/- 1.8 at day 28 (-24.6%, p < 0.0001). Significant and rapid improvements were noted in the sleep interference score (p < 0.00001), Short Questionnaire on Current Burden (p < 0.01) and SF-12 (somatic score p < 0.001; psychological score p < 0.01). Pregabalin was well tolerated, and only three patients (5%) discontinued treatment prematurely. CONCLUSIONS: Our findings suggest that pregabalin is an effective and well-tolerated drug in difficult-to-treat NeP patients under daily clinical practice conditions. A flexible dosing approach appears appropriate to ensure patient compliance and treatment success.

Nitric oxide and pro-inflammatory cytokines correlate with pain intensity in chronic pain patients.

OBJECTIVE: Inflammatory cytokines as well as nitric oxide (NO) play a key role in the pathogenesis of persistent and exaggerated pain states. To document this, we investigated whether a range of cytokines and NO were detectable in the plasma of chronic pain patients and whether cytokine and NO levels correlated with pain severity. METHODS: Plasma samples of 94 chronic pain patients and 6 healthy volunteers were obtained. Average pain intensity during the last 24 h was assessed on a 11-point numeric rating scale and patients were distributed to three groups: light, moderate and severe pain. The concentrations of TNF-alpha, GM-CSF, interleukin (IL)-1beta, IL-6, IL-8, interferon (IFN)-gamma, IL-2, IL-4, IL-5, IL-10 and nitrate/nitrite were determined. RESULTS: Patients with light pain demonstrated significantly increased levels of IL-6 compared to controls. In the severe pain group IL-6 and nitrate/nitrite were significantly increased. Serum concentrations of IL-1beta, TNF-alpha, IL-2 and IL-4 were increased but as we adjusted the level of significance at p = 0.0045, most cytokine plasma levels failed to reach statistical significance. CONCLUSIONS: Pro-inflammatory cytokines (IL-1beta, IL-2, IL-6, IFN-gamma, TNF-alpha) in the plasma correlate with increasing pain intensity. Chronic pain patients show a significant increase in plasma levels of NO in comparison to healthy controls.

The effect of mirtazapine in patients with chronic pain and concomitant depression.

OBJECTIVE: To evaluate the safety, tolerability and efficacy of mirtazapine in patients with the primary diagnosis of chronic pain and concomitant depression in an open post-marketing surveillance study. RESEARCH DESIGN AND METHODS: 594 patients with a primary diagnosis of at least one chronic pain syndrome (minimum duration of 3 months) and the diagnosis of concomitant depression, appropriately made by a neurologist or psychiatrist, were recruited at psychiatric and/or neurological outpatient facilities throughout Germany. The primary efficacy parameter was pain at baseline and endpoint using a patient self-assessment scale. Secondary analyses were performed at baseline, week 1 (day 7 +/- 2), week 4 (day 28 +/- 4) and at endpoint (day 42 +/- 4 or early termination) and included safety and tolerability assessments. Investigators rated the severity of different potential co-morbidities (including depression) with a four-step rating scale (not present, mild, moderate, severe). RESULTS: 594 patients were enrolled and treated with mirtazapine (mean daily dose of 34.5 +/- 10.4 mg at study endpoint). A statistically significant (p < 0.0001; one sample sign test) reduction of pain from baseline to endpoint was found for the overall population. The percentage of patients free of pain or with only moderate pain increased significantly, irrespective of patients' age or pain syndromes. Furthermore, we found a substantial improvement from baseline to endpoint regarding co-morbidities such as sleep disturbance, irritability and exhaustion. The number of adverse events was low (<7%; n = 37), with fatigue (n = 13) and weight gain (n = 11) occurring most frequently. No previously-unknown side effects occurred. One hundred and six patients (18%) discontinued mirtazapine during the study. The main reason was lack of efficacy (6%, n = 33), which may be a reflection of sub-optimal response to the anti-depressant or analgesic effect of the drug, but no appropriate rating scale was used to clarify this question. Only a small number of patients stopped the drug due to adverse events (3%; n = 15). At study endpoint, the majority of physicians and patients rated the overall efficacy and tolerability of mirtazapine as good or very good. Most patients (80%) continued the therapy after 6 weeks. CONCLUSIONS: Despite the limitations of an open observational study, our findings suggest that mirtazapine is a safe and well-tolerated drug for use in daily clinical practice. It still remains unclear whether the reduction of pain, the enhancement of the depressed mood or the combination of both effects led to these results. Nevertheless, our data point to a potential beneficial effect of mirtazapine in the treatment of patients with pain and concomitant depression. However, more systematic research, including placebo-controlled studies, and further empirical testing are necessary.

[Effectiveness and time to onset of pregabalin in patients with neuropathic pain]. / Wirksamkeit und Wirkungsbeginn von Pregabalin bei Patienten mit neuropathischen Schmerzen.

BACKGROUND: The data from a previously published 12-week randomised, double-blind, placebo-controlled multicentre study on the efficacy and safety of pregabalin were analyzed for time to onset of analgesic action with neuropathic pain. PATIENTS AND METHODS: A total of 338 patients with postherpetic neuralgia or painful diabetic peripheral neuropathy were treated with flexible or fixed regimens of pregabalin at daily doses of up to 600 mg/day (n=141 and 132, respectively) or placebo (n=65). RESULTS: Under fixed dose treatment, a decrease of one full point on the 11-point numerical rating pain scale was reached on day 1, two full points on day 13, and three full points on day 23 (under flexible dose pregabalin: on days 6, 17 and 30). In both treatment arms, pain reduction was statistically significant (P=0.001, P=0.002 vs placebo, respectively). CONCLUSION: In patients with chronic neuropathic pain, the analgesic effect of both pregabalin treatment regimens was high and associated with a rapid time to onset.

[Are polymorphisms in the mu-opioid receptor important for opioid therapy?]. / Sind mu-Opioidrezeptorpolymorphismen wichtig für die Opioidtherapie?

Polymorphisms in the mu-opioid receptor gene may potentially alter the clinical effects of opioid analgesics. A common mu-opioid receptor polymorphism occurring at an allelic frequency of 12% decreases the potency of opioid analgesics in humans. Interestingly, in carriers of this mutation, it appears to be possible to reach analgesia by increasing the opioid dose but side effects appear to occur less often despite the higher opioid dose. This suggests a broadened therapeutic range of the opioids. Other mutations of the mu-opioid receptor, for example three mutations within the third intracellular loop of the receptor, impair receptor signaling, but they are too rare to greatly affect pain therapy or have not yet been investigated in the context of pain therapy.

[WHO step II-clinical reality or a didactic instrument?]. / WHO stufe II-Klinische Realität oder didaktisches Instrument?

INTRODUCTION: In 1986 the World Health Organisation (WHO) proposed an analgesic ladder for the effective therapy of cancer pain. The three standard analgesics making up this ladder are aspirin (non-opioid), codeine (weak opioid) and morphine (strong opioid). Adjuvant drugs may be added at any level. However, before 1986 step II analgesics (weak opioids) had never been tested in cancer pain relief. METHODS: This report presents a computer-assisted Medline (US National Library of Medicine) literature search restricted to the years 1986-1994, which was conducted to test the validity of the WHO guidelines, and in particular that of step II. RESULTS: We found seven retrospective studies and one prospective study on cancer pain treatment according to the proposed WHO guidelines that had been published since 1986. Every publication decribed the use of all three steps of the analgesic ladder. We found no prospective controlled trials demonstrating the efficacy and safety of WHO step II in particular. DISCUSSION: The use of the WHO guidelines "by mouth, by the clock and by the ladder" is now the mainstay of cancer pain management. Because of the guidelines' simplicity they found general acceptance and helped to establish an international pain therapy standard for worldwide use. Nevertheless, there is no scientific validation of WHO step II. In the absence of prospective controlled randomized trials additional longterm results are necessary. We need more data on the use of WHO step II and an update of the published guidelines taking account of modern sustained-release drugs. Up to now, step II of the WHO guidelines for cancer pain is not a clinical reality but at best a didactic instrument.