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Effectiveness and cost-effectiveness of duloxetine added to usual care for patients with chronic pain due to hip or knee osteoarthritis: protocol of a pragmatic open-label cluster randomised trial (the DUO trial)


Introduction Osteoarthritis (OA) is a highly prevalent painful condition of the musculoskeletal system. The effectiveness of current analgesic options has proven to be limited and improved analgesic treatment is needed. Several randomised placebo-controlled trials have now demonstrated the efficacy of duloxetine, an antidepressant with a centrally acting effect, in the treatment of OA pain. The aim of the current study is to investigate if duloxetine is effective and cost-effective as a third-choice analgesic added to usual care for treating chronic pain compared with usual care alone in general practice.

Methods and analysis A pragmatic open, cluster randomised trial is conducted. Patients with pain due to hip or knee OA on most days of the past 3 months with insufficient benefit of non-steroidal anti-inflammatory drugs or contraindications or intolerable side effects are included. General practices are randomised to either (1) duloxetine and usual care or (2) usual care only. Primary outcome is pain at 3 months measured on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. Secondary outcomes at 3 months and 1 year are pain (WOMAC, at 1 year), function (WOMAC), adverse reactions, quality of life and modification of the response to treatment by the presence of centrally sensitised pain (modified PainDETECT). At 1 year, medical and productivity costs will be assessed. Analyses will be performed following the intention-to-treat principle taking the cluster design into account.

Ethics and dissemination The study is approved by the local Medical Ethics Committee (2015–293). Results will be published in a scientific peer-reviewed journal and will be communicated at conferences.

Trial registration number Dutch Trial Registry(ntr4798); Pre-results.

  • primary care
  • pain management
  • clinical trials
  • rheumatology

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  • Contributors JJvdD, DS, PAJL, ARK, MAK, PJEB, SMAB-Z participated in the design of the study and the research protocol. JJvdD and DS will coordinate the study, are responsible for data acquisition and will conduct statistical analysis. MAK will provide economic statistical consultation. JJvdD, DS, PAJL, ARK, MAK, PJEB and SMAB-Z were involved in the writing, editing and approval of the final manuscript.

  • Funding This work was supported by the Netherlands Organisation for Health Research and Development (ZonMW) (80-83600-98-3141).

  • Competing interests None declared.

  • Ethics approval The local Medical Ethics Committee of Erasmus Medical Center has approved the trial (MEC-2015-293), which is registered in the Dutch Trial registry (NTR4798) and EudractCT database (2015-001669-16).

  • Provenance and peer review Not commissioned; peer reviewed for ethical and funding approval prior to submission.

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