Summary Background Neuropathic pain is difficult to treat. New treatments, clinical trials and standards of quality for assessing evidence justify an update of evidence-based recommendations for its pharmacological treatment. Methods The Neuropathic Pain Special Interest Group (NeuPSIG) of the International Association for the Study of Pain conducted a systematic review of randomised double-blind studies of oral and topical pharmacotherapy for neuropathic pain, including unpublished trials (retrieved from clinicaltrials.gov and pharmaceutical websites). Meta-analysis used Numbers Needed to Treat (NNT) for 50 % pain relief as primary measure and assessed publication bias. Recommendations used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Findings In total 229 studies were included. Analysis of publication bias suggested a 10% overstatement of treatment effects. Studies published in peer-review journals reported greater effects than online studies (R2=9·3%, p<0·01). Trial outcomes were generally modest even for effective drugs : in particular NNTs were 3·6 (95 % CI 3·0–4·4) for tricyclic antidepressants (TCAs), 6·4 (95 % CI 5·2–8·4) for serotonin- noradrenaline reuptake inbibitor (SNRI) antidepressants duloxetine and venlafaxine, 7·7 (95 % CI 6·5–9·4) for pregabalin and 6·3 (95 % CI 5·0–8·3) for gabapentin. NNTs were higher for gabapentin ER/enacarbil and capsaicin high concentration patches, lower for opioids and botulinum toxin A (BTX-A) and undetermined for lidocaine patches. Final quality of evidence was lower for lidocaine patches and BTX-A. Tolerability/safety and values/preferences were high for lidocaine patches and lower for opioids and TCAs. This permitted a strong GRADE recommendation for use and proposal as first line for TCAs, SNRIs, pregabalin, gabapentin and gabapentin ER/enacarbil in neuropathic pain, a weak recommendation for use and proposal as second line for lidocaine patches, capsaicin patches and tramadol, and a weak recommendations for use and proposal as third line for strong opioids (particularly oxycodone and morphine) and BTX-A. Data for cannabinoids, tapentadol, drug combinations, and several other antiepileptics, antidepressants and topical drugs were inconclusive. Interpretation Limited efficacy, large placebo responses, inadequate diagnostic criteria and poor phenotypic profiling probably account for modest trial outcomes and should be taken into account in future studies. Funding This study was funded by NeuPSIG.

Few studies have directly compared the clinical features of neuropathic and non-neuropathic pains. For this purpose, the French Neuropathic Pain Group developed a clinician-administered questionnaire named DN4 consisting of both sensory descriptors and signs related to bedside sensory examination. This questionnaire was used in a prospective study of 160 patients presenting with pain associated with a definite neurological or somatic lesion. The most common aetiologies of nervous lesions (n=89) were traumatic nerve injury, post herpetic neuralgia and post stroke pain. Non-neurological lesions (n=71) were represented by osteoarthritis, inflammatory arthropathies and mechanical low back pain. Each patient was seen independently by two experts in order to confirm the diagnosis of neuropathic or non-neuropathic pain. The prevalence of pain descriptors and sensory dysfunctions were systematically compared in the two groups of patients. The analysis of the psychometric properties of the DN4 questionnaire included: face validity, inter-rater reliability, factor analysis and logistic regression to identify the discriminant properties of items or combinations of items for the diagnosis of neuropathic pain. We found that a relatively small number of items are sufficient to discriminate neuropathic pain. The 10-item questionnaire developed in the present study constitutes a new diagnostic instrument, which might be helpful both in clinical research and daily practice.