Xiao 2009.

Methods	Randomised, double‐blind, placebo‐controlled trial 2 treatment arms: 1 PCB and 1 LEV Randomisation concealment: numbered containers containing either LEV or PCB. Random list generation: randomisation codes were generated by the study sponsor. Each patient who qualified to receive double‐blind treatment was assigned a randomisation number and given LEV or PCB accordingly Blinding: identical tablets and packages. Investigators were described as blinded to treatment assignment Baseline: 8 weeks. Treatment period = 16 weeks (4 weeks' titration, 12 weeks' maintenance)
Participants	All adults. Single centre (China) Total randomised 56 adults; all with drug‐resistant focal epilepsy 28 adults to PCB 28 adults to LEV 3000 mg 42.9% male in PCB, 42.9% male in LEV Age range 16 to 70 years Other AEDs: 1 or 2 ≥ 4 focal seizures per month over preceding 2 months ≥ 10 weeks' background AED treatment Mean duration of epilepsy (± SD) (years): LEV = 14.1 ± 9.4 (range 2 to 40), PCB = 16.1 ± 12.5 (range 2 to 48) Mean baseline seizure frequency per week: LEV 4.9; range 1 to 23.6, PCB 5.6; range 1 to 50
Interventions	LEV 3000 mg PCB add‐on Up‐titration dosages: received LEV 1000 mg/day (administered twice a day) and increased to 2000 mg/day after 2 weeks, and to 3000 mg/day after another 2 weeks
Outcomes	≥ 50% reduction in seizure frequency Treatment withdrawal Adverse effects
Notes	2 LEV‐treated patients decreased dose to 2000 mg (owing to adverse effects)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	B ‐ Unclear
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