Zhou 2008.

Methods	Randomised, double‐blind, placebo‐controlled trial 2 treatment arms: 1 PCB and 1 LEV Randomisation concealment: participants received an exclusive random number consecutively on entry into the study, and received treatment on the basis of this random number. Random list generation: random numbers table Blinding: described as double‐blind with no further specification. Medications were supplied and packaged by UCB S.A|. Pharma Baseline: 8 weeks. Treatment period = 16 weeks (4 weeks' titration, 12 weeks' maintenance)
Participants	All adults. 1 centre in China. Total randomised 28 adults 14 adults to PCB 14 adults to LEV 3000 mg 55% male in PCB, 54% male in LEV Age range 16 to 70 years. Other AEDs: 1 or 2 ≥ 8 seizures during 8‐week baseline with 2 per 4 weeks Mean duration of epilepsy (± SD) (years): LEV = 8.7 ± 6.4, PCB = 16.5 ± 7.2 Mean baseline seizure frequency per week (± SD) 6.55 ± 10.79 in LEV, 6.15 ± 11.20 in PCB
Interventions	LEV 3000 mg/day PCB add‐on Up‐titration dosages: 500 mg twice daily in the first 2 weeks, 1000 mg twice daily in the third and fourth weeks)
Outcomes	≥ 50% reduction in seizure frequency Treatment withdrawal Cognitive function QoL
Notes	Cognitive function assessment was with a battery of neuropsychological tests: Wisconsin Card Sorting Test, Verbal Fluency, Trail Making Test, Digit Symbol, Stroop Color–Word Interference Task, Logic Memory, Delayed Logic Memory, Visual Memory, Delayed Visual Memory, Calculation QoL assessment was with the use of QOLIE‐31 Drop‐outs (1 in LEV, 3 in PCB) were excluded from the study author's analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	A ‐ Adequate
Allocation concealment (selection bias)	Low risk	A ‐ Adequate
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	B ‐ Unclear
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	B ‐ Unclear
Incomplete outcome data (attrition bias) All outcomes	Low risk	A ‐ Adequate
Selective reporting (reporting bias)	Low risk	A ‐ Adequate

AEDs: antiepileptic drugs; CBCL: Achenbach Child Behavior Checklist; CHQ‐PF50: Child Health Questionnaire‐Parent Form 50;

ESI: Epilepsy Surgery Inventory scale;

IQR: interquartile range;

ITT: intention to treat;

Leiter‐R AM: Leiter International Performance Scale‐Revised Attention and Memory; LEV: levetiracetam; Leiter‐R ERS: Leiter International Performance Scale‐Revised, Examiner’s Rating Scale;

PCB: placebo;

QOLIE: Quality of life in epilepsy inventory ;

QoL: quality of life;

WRAML‐2: Wide Range Assessment of Memory and Learning‐2;

XR: extended release.