Lamotrigine add-on therapy for drug-resistant focal epilepsy

Background This is an updated version of a Cochrane Review last updated in 2020. Epilepsy is a common neurological disorder, affecting 0.5% to 1% of the population. In nearly 30% of cases, epilepsy is resistant to currently available drugs. Pharmacological treatment remains the first choice to control epilepsy. Lamotrigine is a second‐generation antiseizure medication. When used as an add‐on (in combination with other antiseizure medications), lamotrigine can reduce seizures, but with some adverse effects. Objectives To evaluate the benefits and harms of add‐on lamotrigine, compared with add‐on placebo or no add‐on treatment in people with drug‐resistant focal epilepsy. Search methods For this update, we searched the Cochrane Register of Studies (CRS Web) and MEDLINE (Ovid) on 3 October 2022 with no language restrictions. CRS Web includes randomised and quasi‐randomised controlled trials from PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform (ICTRP), Cochrane Central Register of Controlled Trials (CENTRAL), and the Specialised Registers of Cochrane Review Groups, including Epilepsy. Selection criteria We included randomised controlled trials (RCTs) that investigated add‐on lamotrigine versus add‐on placebo or no add‐on treatment in people of any age with drug‐resistant focal epilepsy. We used data from the first period of eligible cross‐over trials. Data collection and analysis For this update, two review authors independently selected trials and extracted data. Our primary outcome was 50% or greater reduction in seizure frequency. Our secondary outcomes were treatment withdrawal, adverse effects, cognitive effects, and quality of life. Primary analyses were by intention‐to‐treat. We performed sensitivity best‐ and worse‐case analyses to account for missing outcome data. We calculated pooled risk ratios (RRs) with 95% confidence intervals (95% Cls) for dichotomous outcomes. Main results We identified no new studies for this update, so the results and conclusions of the review are unchanged. We included five parallel‐group studies in adults or children, eight cross‐over studies in adults or children, and one parallel study with a responder‐enriched design in infants. In total, these 14 studies enroled 1806 eligible participants (38 infants, 199 children, 1569 adults). Baseline phases ranged from four to 12 weeks and treatment phases ranged from eight to 36 weeks. We rated 11 studies (1243 participants) at low overall risk of bias and three (697 participants) at unclear overall risk of bias due to lack of information on study design. Four studies (563 participants) reported effective blinding. Lamotrigine compared with placebo probably increases the likelihood of achieving 50% or greater reduction in seizure frequency (RR 1.80, 95% CI 1.45 to 2.23; 12 trials, 1322 participants (adults and children); moderate‐certainty evidence). There is probably little or no difference in risk of treatment withdrawal for any reason among people treated with lamotrigine versus people treated with placebo (RR 1.11, 95% CI 0.91 to 1.37; 14 trials; 1806 participants; moderate‐certainty evidence). Lamotrigine compared with placebo is probably associated with a greater risk of ataxia (RR 3.34, 99% Cl 2.01 to 5.55; 12 trials; 1525 participants; moderate‐certainty evidence), dizziness (RR 1.76, 99% Cl 1.28 to 2.43; 13 trials; 1768 participants; moderate‐certainty evidence), nausea (RR 1.81, 99% CI 1.22 to 2.68; 12 studies, 1486 participants; moderate‐certainty evidence), and diplopia (RR 3.79, 99% Cl 2.15 to 6.68; 3 trials, 944 participants; moderate‐certainty evidence). There is probably little or no difference in the risk of fatigue between lamotrigine and placebo (RR 0.82, 99% CI 0.55 to 1.22; 12 studies, 1552 participants; moderate‐certainty evidence). Authors' conclusions Lamotrigine as an add‐on treatment for drug‐resistant focal seizures is probably effective for reducing seizure frequency. Certain adverse effects (ataxia, dizziness, diplopia, and nausea) are probably more likely to occur with lamotrigine compared with placebo. There is probably little or no difference in the number of people who withdraw from treatment with lamotrigine versus placebo. The trials were of relatively short duration and provided no long‐term evidence. In addition, some trials had few participants. Further trials are needed to assess the long‐term effects of lamotrigine and to compare lamotrigine with other add‐on drugs.