Date	Event	Description
16 July 2009	New search has been performed	The report of one trial previously in 'ongoing studies' is now available (Pérez‐Bárcena 2008). The results of the trial have been included in the review. The results and discussion sections have been updated accordingly.
5 May 2009	New search has been performed	The search was updated to January 2008. No new trials were identified. The conclusions remain the same.
17 July 2008	Amended	Converted to new review format.
15 March 2006	New search has been performed	An updated search for new trials was conducted in March 2006. One ongoing trial (Pérez‐Bárcena 2005) was identified, the findings from which will be incorporated into the review when available.