Schapel 1993.

Methods	Randomised, double‐blind, cross‐over study. Two treatment arms: 1 placebo, 1 lamotrigine. Pre‐randomization baseline = 12 weeks. Treatment I and II = 12 weeks each. Washout I and II = 4 weeks each, including 1 week taper.
Participants	Multicentre Australian study. 41 participants (21 males and 20 females) with drug‐resistant partial seizures 20 were randomised to receive placebo and 21 to lamotrigine. The age ranged from 17 to 63 (median 28) years. The mean age at onset was 10.4 +/‐9.6 years. Maximum number of other AEDs permitted = 3. People receiving valproate monotherapy were excluded.
Interventions	Add‐on lamotrigine or placebo. Median daily dose of lamotrigine was 300 mg. Participants receiving valproate received lower doses.
Outcomes	(1) 50% responder rates. (2) Withdrawal from study for any reason. (3) Adverse effects.
Notes	Banks 1991 is linked to this study and investigated cognitive functions (concentration and attention; general cerebral efficiency; mnestic function).
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	No details provided regarding blinding of participants, study personnel, and outcome assessors. All treatments and packaging were identical. Pre‐packed coded medication dispensed by pharmacy.
Incomplete outcome data (attrition bias)	Low risk	No participants were excluded from analysis. None withdrew from the study.
Selective reporting (reporting bias)	Low risk	Protocol unavailable, but appears all expected and pre‐specified outcomes were reported.
Other bias	Unclear risk	This study was sponsored by GlaxoSmithKline, the manufactures of LTG.