Ben‐Menachem 2000.

Methods	Randomised double‐blind placebo‐controlled parallel trial 2 treatment arms: 1 PCB and 1 LEV Randomisation concealment: telephone randomisation. Random list generation: centralised minimisation procedure of an unbalanced randomisation list (1 PCB:2 LEV) Blinding: identical tablets and packages. Investigators were described as blinded to treatment assignment. If treatment code was broken, the patient had to be removed from the trial Baseline = 12 weeks. Treatment period = 16 weeks (4 weeks' titration, 12 weeks' maintenance)
Participants	All adults. Multicentre across Europe Total randomised 286 adult; all with drug‐resistant focal epilepsy 105 adults to PCB 181 adults to LEV 3000 mg 48% male Age range 17 to 70 years Other AEDs = 1 ≥ 2 focal seizures per 4 weeks during 12‐week baseline ≥ 1‐year history of focal epilepsy Mean duration of epilepsy (± SD) (years): LEV = 19 ± 11; PCB = 19 ± 12; overall = 19 ± 11 Median baseline seizure frequency per week: 1.70; range 0.3 to 1.7
Interventions	LEV 3000 mg/day PCB Up‐titration dosages = titrated upwards every 2 weeks from 500 mg twice daily to the target dosage of 1500 mg twice daily
Outcomes	≥ 50% reduction in seizure frequency Treatment withdrawal Adverse effects
Notes	2 participants excluded from 50% responder analysis: 1 from the LEV 3000‐mg, 1 from the PCB
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	Low risk	A ‐ Adequate
Blinding of outcome assessment (detection bias) All outcomes	Low risk	A ‐ Adequate
Incomplete outcome data (attrition bias) All outcomes	Low risk	A ‐ Adequate
Selective reporting (reporting bias)	Low risk	A ‐ Adequate