Study	Reason for exclusion
Gines 1990	Spain Randomised clinical trial. Through communication with the first author it was clarified that the patients did not have upper gastrointestinal bleeding.
Goulis 1998	UK Observational study. Not a randomised trial.
Henrion 1992	Belgium Controlled clinical study. Inadequate allocation concealment, alternate method.
Husova 2005	Czech Republic Observational study. Not a randomised trial.
Novella 1997	Spain Randomised clinical trial. Through communication with the first author it was clarified that the patients did not have upper gastrointestinal bleeding.
Pohl 2004	Germany Retrospective cohort study.
Pulanic 1989	Yugoslavia Randomised clinical trial. No clinical outcomes, only laboratory variables after antibiotic prophylaxis.
Wilbur 2005	Canada Retrospective cohort study.
Zhao 2002	China Not a randomised trial.

RCT ‐ randomised clinical trial. 
 CCT ‐ controlled clinical trial.