Davis 1997.

Study characteristics
Methods	Dose‐ranging double‐blinded RCT
Participants	33 preterm infants in the USA enrolled in 1994 ‐ 1995 with birth weight 700 g to 1300 g, less than 24 hours old, intubated and on mechanical ventilation for treatment of respiratory distress syndrome. Had received surfactant within first 24 hours of life.
Interventions	Three groups: Experimental group 1: SOD 2.5 mg/kg (n = 11) Experimental group 2: SOD 5 mg/kg (n = 11) In both these groups the drug was given intratracheally, repeated every 48 hours until extubated or until seven doses completed, whichever was earlier. Control group: equal volume of saline intratracheally, repeated every 48 hours until extubated or until seven doses completed, whichever was earlier (n = 11). The initial drug or placebo was administered in 2 aliquots over a 1‐minute period within 30 to 120 minutes after surfactant administration. If infants were extubated before 14‐days of age, then the study drug was discontinued. However, if infants were re‐intubated before 14‐days of age, additional doses were administered every 48 hours until 14‐days of life. rhSOD or placebo was never administered after 14‐days of life.
Outcomes	SOD concentration in serum, TA and urine, neutrophil chemotactic activities, anti rhSOD antibodies, severity of RDS, IVH all grades, IVH grade 3‐4, NEC, apnea, PDA, ROP, renal failure, BPD, sepsis, mortality at 28 days, overall mortality, total days of oxygen, duration of mechanical ventilation.
Funding sources / declarations of interest	Funding and conflicts of interest not reported.
Notes	Small sample size. In this review we combined the data from patients from both dosage regimens as no dose‐response relationship was evident in the results.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described in sufficient detail in text.
Allocation concealment (selection bias)	Unclear risk	Not described in text.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded study and placebo was used.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blinded study. Additionally, (quote;) "Chest radiographs and cranial ultrasounds were interpreted by a single pediatric radiologist who was also blinded to treatment assignment."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No patients lost to follow up.
Selective reporting (reporting bias)	Unclear risk	Protocol not available.
Other bias	Unclear risk	Imbalances in group characteristics.