Jawad 1989.

Methods	Randomised, double‐blind, cross‐over study. Two treatment arms: 1 placebo, 1 lamotrigine. Five phases: baseline period = 8 weeks; Treatment I = 12 weeks; Washout I = 6 weeks; treatment II = 12 weeks; Washout II = 6 weeks.
Participants	Single centre study from UK. 24 adults with refractory drug‐resistant partial seizures, aged between 16 to 60 years. 12 were allocated to lamotrigine and 12 to placebo in the first treatment phase. Maximum number of other AEDs = 2.
Interventions	Add‐on lamotrigine or placebo. The median daily dose of lamotrigine was 250 mg. Participants on valproate received lower doses. Unblinded investigator wrote prescriptions based on plasma concentration.
Outcomes	(1) 50% responder rates. (2) Withdrawal from study for any reason. (3) Adverse effects.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random permuted blocks.
Allocation concealment (selection bias)	Low risk	Partcipants were allocated by sequentially numbered, sealed packages containing either lamotrigine or placebo.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No details provided regarding blinding of participants, study personnel, and outcome assessors. Identical tablets and packaging used.
Incomplete outcome data (attrition bias)	Low risk	No participants were excluded from analysis. One participant who was allocated to lamotrigine withdrew from the study (the reason for exclusion was reported) and none withdrew from the placebo group.
Selective reporting (reporting bias)	Low risk	All outcomes stated in methods section of paper were reported in the results. There was no protocol available to check a priori outcomes.
Other bias	Unclear risk	This study was sponsored by GlaxoSmithKline, the manufactures of LTG.