Ramsay 1992

Methods	Parallel trial Study conducted at 16 centres in the United States Participants assigned via randomisation tables within each centre in a 2:1 ratio (SV:PHT) Method of allocation concealment not stated Unblinded
Participants	Participants with at least 2 newly diagnosed and previously untreated primary generalised tonic‐clonic seizures within 14 days of starting the trial Number randomised: PHT = 50; SV = 86 0% participants with partial epilepsy, 73 (54%) men Mean age (range): 21 (3‐64 years). Participants followed up for up to 6 months
Interventions	Monotherapy with PHT or SV Starting doses PHT: 3‐5 mg/kg/day, SV: 10‐15 mg/kg/day, doses gradually increased Doses achieved not stated
Outcomes	Time to first generalised tonic‐clonic seizure 6‐month seizure recurrence rates Adverse events
Notes	IPD provided for 3/4 outcomes of this review (maximum follow‐up 6 months, therefore trial cannot contribute to outcome 'Time to achieve 12‐month remission')
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants randomised on a 2:1 ratio SV:PHT using randomisation tables in each centre (information provided by trial author)
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label trial; authors state that differences in adverse events of PHT and SV would "quickly unblind" the trial anyway
Blinding of outcome assessment (detection bias) All outcomes	High risk	Open‐label trial, authors state that differences in adverse events of PHT and SV would "quickly unblind" the trial anyway
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition rates reported, all randomised participants analysed from IPD provided (see footnote 2)
Selective reporting (reporting bias)	Low risk	All outcomes reported or calculated with IPD provided (see footnote 2)
Other bias	Low risk	No other bias detected