Lee 1989.

Methods	Randomised, double‐blind, placebo‐controlled trial 2 treatment arms: PHT and placebo Patients randomised using random digits, all participants received identical medication Treatment period: 3 days. No follow‐up of participants
Participants	Adults, mean age 39.9 years (PHT) and 37.5 years (placebo) all undergoing intracranial, supratentorial surgery. Participants had no history of seizures and not taking AEDs prior to surgery. 400 participants randomised: 189 to PHT and 185 to placebo. 26 died prior to treatment
Interventions	Group 1: PHT 15 mg/kg for 15‐20 min prior to wound closure followed by 5‐6 mg/kg/day, 3 times daily in first 3 postoperative days Group 2: saline solution administered as described above
Outcomes	Primary outcome: efficacy (number of seizures at 3 days)
Notes	26 participants randomised died prior to treatment, excluded from all data exploration and analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Used random digits, unclear how generated, whether open list, etc
Allocation concealment (selection bias)	Unclear risk	No details in text
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Identical medication used for both groups. Adequate blinding methods for key personnel and participants
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear details on study attrition rate and how data analysed
Selective reporting (reporting bias)	Unclear risk	No protocol available
Other bias	Low risk	No other bias detected