Bohn 1989.

Methods	Randomised controlled trial.
Participants	Children (age 1‐18 years) with severe head injury (GCS ≤ 7). 82 people were included in the trial, 41 in each study group.
Interventions	High‐dose phenobarbitone (loading dose 50 mg/kg followed by 20 mg/kg/day) or no phenobarbitone.
Outcomes	Death and GOS were measured at the time of hospital discharge and at 6 months, ICP, sepsis.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Review authors' judgement: Experiencing a head injury occurs randomly.
Allocation concealment (selection bias)	High risk	Correspondence with author in 1997. Quote: "Patients allocated to treatment group according to which ICU physician was on duty."
Blinding (performance bias and detection bias) Participants	Low risk	Review authors' judgement: Low risk as people had a Glasgow Coma Scale score of 7 or less and therefore had reduced cognitive function.
Blinding (performance bias and detection bias) Treating physicians	Unclear risk	Not stated.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome data on mortality and disability are reported in full.
Selective reporting (reporting bias)	Unclear risk	Review authors' judgement: Not assessed as we were unable to obtain the study protocol. The authors report there was a study protocol.
Other bias	Unclear risk	Review authors' judgement: None known.