Demetriades 1991.

Methods	Parallell, randomised study in a secondary care hospital in South Africa
Participants	Participants with penetrating abdominal trauma who underwent laparotomy Excluded from study if allergy to study antibiotic, delay to theatre of > 12 hours, or injuries requiring antibiotic not in study protocol 123 participants in total: 60 in group 1, mean age 28 years; 63 in group 2, mean age 30 years
Interventions	Group 1: Ceftriaxone 1 g IV, once daily Group 2: Cefoxitin 1 g IV, 6 hourly In both groups, antibiotics continued for 24 hours if no colonic injury, and for 48 hours if colonic injury present
Outcomes	Developement of: abdominal sepsis pneumonia urinary tract infection
Notes	No funding source reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"patients were randomised" ‐ no details
Allocation concealment (selection bias)	Unclear risk	no mention of allocation concealment made in the paper
Blinding of participants and personnel (performance bias) All outcomes	High risk	different dosing regimens, with no placebo mentioned
Blinding of outcome assessment (detection bias) All outcomes	High risk	outcome assessors not blinded to allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	no dropouts
Selective reporting (reporting bias)	Unclear risk	no protocol or trial registration available
Other bias	High risk	Unequal numbers of participants with bullet wounds or > 3 organs injured