Ramsey 1992

Methods	Open‐label, parallel‐design, multicentre RCT conducted at 16 centres in the USA 2 treatment arms: PHT and VPS randomised in a 2:1 ratio
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, VPS = 86 73 male participants (54%) 0% participants with partial epilepsy (all generalised epilepsy) Mean age (range): 21 (3‐64 years)
Interventions	Monotherapy with PHT or VPS Starting doses PHT: 3 mg/kg/d‐ 5 mg/kg/d, VPS: 10 mg/kd/d‐15 mg/kg/d, doses gradually increased. Doses achieved not stated Range of follow‐up: 0‐11 months
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 by the Department of Veteran's Affairs (maximum follow‐up 6 months, therefore trial could not contribute to outcome, 'Time to 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 VPS: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; trial authors state that differences in adverse events of PHT and VPS would "quickly unblind" the trial anyway
Blinding of outcome assessment (detection bias) All outcomes	High risk	Open‐label trial; trial authors state that differences in adverse events of PHT and VPS 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	None identified