Vigabatrin versus carbamazepine monotherapy for epilepsy

Abstract

The efficacy and safety of vigabatrin (VGB) as an add-on therapy for refractory epilepsy has been well established. However, this needs to be weighed against the risk of the development of visual field defects. Whether VGB monotherapy is an effective and safe treatment compared with the standard antiepileptic drug carbamazepine (CBZ) monotherapy for epilepsy has not been systematically reviewed. To investigate the efficacy and safety of VGB versus CBZ monotherapy for epilepsy. We searched the Cochrane Epilepsy Group Specialized Register (10 October 2011), the Cochrane Central Register of Controlled Trials (CENTRAL Issue 4 of 4, The Cochrane Library 2011) and MEDLINE (1948 to week 4, September 2011), EMBASE (1974 to January 2011) and the Chinese Biomedical Database (CBM) (1979 to January 2011). We searched trials registers and contacted themanufacturer of VGB and authors of included studies for additional information. There were no language restrictions. Randomised controlled trials (RCTs) comparing VGB with CBZ monotherapy for epilepsy. Two review authors independently assessed trial quality and extracted data. The primary outcome was time to treatment withdrawal. The secondary outcomes were time to achieve six- and 12-month remission after randomisation, time to first seizure after randomisation and adverse events. Results were presented as hazard ratio (HR) with 95% confidence intervals (CI) (time to event data) or risk ratio (RR) with 95%CI (adverse events). Five studies involving a total of 734 participants were eligible for inclusion. We assessed only one study as having good quality while the other four were of poor quality. However, it was difficult to perform a meta-analysis by extracting aggregate data to synthesise the results as originally planned, mainly because not all the studies reported the same outcomes as those chosen for this review. There was no significant difference favouring either VGB or CBZ in terms of time to treatment withdrawal and time to achieve six-month remission after dose stabilisation from randomisation, but results did show a disadvantage for VGB on time to first seizure after randomisation. Compared with CBZ, taking VGB was associated with more occurrences of weight gain and less occurrences of skin rash and drowsiness. There were no differences in visual field defects and visual disturbances. There is currently insufficient data to address the risk-benefit balance of using VGB versus CBZ monotherapy for epilepsy. Considering the high prevalence of visual field defects, reported in an existing systematic review of observational studies (Maguire 2010), the prescribing of VGB monotherapy for epilepsy should be used with caution and not considered as a first-line choice. If necessary, a frequent assessment of visual field isneeded. Future research should focus on investigating the reasons for visual field defects and exploring the potential prevention strategies. Moreover, future monotherapy studies of epilepsy should report results according to the recommendation of International League Against Epilepsy (ILAE) Commission, and methodological quality should be improved.