For the 2010 review we would like to thank the staff of the Cochrane Pain, Palliative & Supportive Care Review Group, including Jessica Thomas, Yvonne Roy, Anna Hobson, Sylvia Bickley for help with refining the search strategy, Caroline Struthers for updating the search, Mari Imamura for translation of two Japanese papers, and our peer referees, Giovambattista Zeppetella and Janet Wale, who commented on the draft of the protocol for this systematic review, and Karl Gallegos, Gerhild Becker and Andrew Moore who commented on the review. Thanks also to Linda Porter and Lyn Jackson (pharmacists) and Susan Merner (librarian) at Poole Hospital NHS Foundation Trust.

For the updated 2013 review we would like to thank Jo Abbott (Trials Search Co‐ordinator), Jane Hayes, Yvonne Roy, Mike Bennett and Phil Wiffen at The Cochrane Collaboration. We would also like to thank the librarians at the Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust, University Hospital Southampton NHS Foundation Trust and Barbara Peirce at Poole Hospital NHS Foundation Trust.

Cochrane Review Group funding acknowledgement: The National Institute for Health Research (NIHR) is the largest single funder of the Cochrane PaPaS Group. Disclaimer: The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, National Health Service (NHS) or the Department of Health.