Messenheimer 1994.

Methods	Randomised, double‐blind, cross‐over study. Two treatment arms: 1 placebo, 1 lamotrigine. Total study duration was 43 weeks. Pre‐randomisation baseline = 8 weeks. Treatment A = 14 weeks (including 2 weeks blinded tapering). Follow‐up period = 3 weeks. Treatment B = 14 weeks (including 2 weeks blinded tapering). Washout = 4 weeks.
Participants	Multi‐centre US study with 98 participants (46 men and 52 women) with drug‐resistant partial epilepsy. 46 were randomised to receive lamotrigine and 52 to placebo in the first treatment phase. Age range 18 to 64 years with a mean of 35. Age at onset of epilepsy was 12 years; mean duration 23.1 years. Up to 3 other AEDs were permitted. Concomitant use of valproate was not allowed.
Interventions	Add‐on lamotrigine or placebo. Median lamotrigine dose 400 mg/day.
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	Participants were allocated by sequentially numbered, sealed packages containing either lamotrigine or placebo.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Investigators were blinded. No more information provided regarding blinding of neurologists, participants, and parents. All treatments (tablets) and packaging were identical. Pre‐packed coded medication dispensed by pharmacy.
Incomplete outcome data (attrition bias)	Low risk	No participants were excluded from analysis. 6 participants withdrew from the study; 2 receiving lamotrigine and 4 receiving placebo. The reasons for exclusion were reported.
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.