Study	Reason for exclusion
Arantes 2009	Included participants over 17 years of age
Ashkenazi 2007	Study ineligible (not designed as a randomised controlled trial)
Bird 2007	Included participants over 17 years of age
Bradley 2007	No placebo
Guan 2013	Adult participants
Gupta 2014	Participant age ranged from 15 to 22 years; we were unable to extract child data
McGaw 1987	Postoperative analgesics only
Minor 2009	Included participants over 17 years of age
Ngan 1994	Included participants over 17 years of age
Patel 2011	Participants were over 17 years of age
Polat 2005a	Included participants over 17 years of age
Polat 2005b	Included participants over 17 years of age