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Effectiveness, cost-effectiveness and safety of gabapentin versus placebo as an adjunct to multimodal pain regimens in surgical patients: protocol of a placebo controlled randomised controlled trial with blinding (GAP study)
  1. Sarah Baos1,
  2. Chris A Rogers1,
  3. Reyad Abbadi2,
  4. Aiman Alzetani3,
  5. Gianluca Casali2,
  6. Nilesh Chauhan4,
  7. Laura Collett1,
  8. Lucy Culliford1,
  9. Samantha E de Jesus1,
  10. Mark Edwards5,6,
  11. Nicholas Goddard5,
  12. Jennifer Lamb1,
  13. Holly McKeon1,
  14. Mat Molyneux4,
  15. Elizabeth A Stokes7,
  16. Sarah Wordsworth7,
  17. Ben Gibbison4,8,
  18. Maria Pufulete1
  1. 1Bristol Trials Centre, Clinical Trials and Evaluation Unit, Bristol Medical School, University of Bristol, Bristol, UK
  2. 2Department of Surgery, University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK
  3. 3Department of Surgery, University Hospital Southampton NHS Foundation Trust, Southampton, UK
  4. 4Department of Anaesthesia, University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK
  5. 5Department of Anaesthesia, University Hospital Southampton NHS FoundationTrust, Southampton, UK
  6. 6Acute, Critical & Perioperative Care Research Group, NIHR Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust/University of Southampton, Southampton, UK
  7. 7Health Economics Research Centre, University of Oxford, Oxford, UK
  8. 8Bristol Medical School, University of Bristol, Bristol, UK
  1. Correspondence to Dr Sarah Baos; sarah.baos{at}


Introduction Gabapentin is an antiepileptic drug currently licensed to treat epilepsy and neuropathic pain but has been used off-label to treat acute postoperative pain. The GAP study will compare the effectiveness, cost-effectiveness and safety of gabapentin as an adjunct to standard multimodal analgesia versus placebo for the management of pain after major surgery.

Methods and analysis The GAP study is a multicentre, double-blind, randomised controlled trial in patients aged 18 years and over, undergoing different types of major surgery (cardiac, thoracic or abdominal). Patients will be randomised in a 1:1 ratio to receive either gabapentin (600 mg just before surgery and 600 mg/day for 2 days after surgery) or placebo in addition to usual pain management for each type of surgery. Patients will be followed up daily until hospital discharge and then at 4 weeks and 4 months after surgery. The primary outcome is length of hospital stay following surgery. Secondary outcomes include pain, total opioid use, adverse health events, health related quality of life and costs.

Ethics and dissemination This study has been approved by the Research Ethics Committee . Findings will be shared with participating hospitals and disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings. Patients will be informed of the results through patient organisations and participant newsletters.

Trial registration number ISRCTN63614165.

  • clinical trials
  • pain management
  • surgery

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  • Contributors SB is involved in conducting the trial and assembled the manuscript from the trial protocol. MP identified the funding opportunity and designed the trial with statistical input from CR. CR is the non-clinical lead and the methodology/statistics lead for the trial. BG is the chief investigator and NC is the clinical pain lead for the trial. LCo drafted the statistical analysis plan. SW is the health economics lead and EAS the health economist working on the trial. SB and EAS designed the data collection for the health economics element of the trial. LCu provides senior trial management oversight and advice. HM, SEdJ and JL have assisted with the set-up and delivery of the trial. RA, AA, GC, ME, NG and MM are participating clinicians in the trial. All authors have been involved in preparation of the study protocol and have read and approved the final manuscript.

  • Funding This study is funded by the National Institute for Health Research Health Technology Assessment Programme (15/101/16). The views and opinions expressed therein arethose of the author(s) and do not necessarily reflect those of the National Institute of Health Research, NHS, or the Department of Health and Social Care.

  • Competing interests No competing interests are declared. At the time that the work was carried out, GC was employed by the University Hospitals Bristol NHS Foundation Trust, Bristol, UK. GC is currently the Medical Director Johnson and Johnson Medical Devices UK and Ireland. GC has no competing interests to declare.

  • Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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