Vigabatrin versus carbamazepine monotherapy for epilepsy

Review question

This review is an update of a review previously published in the Cochrane Database of Systematic Reviews (2012, Issue 1) titled 'Vigabatrin versus carbamazepine monotherapy for epilepsy'. We reviewed the evidence on the efficacy and safety of vigabatrin versus carbamazepine (CBZ) when used as monotherapy for epilepsy. We found five studies.

Background

Epilepsy is a common neurological disorder, affecting more than 50 million people worldwide. The efficacy and safety of vigabatrin as an add-on therapy for refractory epilepsy have been well established. However, this information needs to be weighed against the risk of development of visual field defects. We wanted to know whether vigabatrin monotherapy is effective and safe compared with the standard antiepileptic drug carbamazepine as monotherapy for epilepsy.

Study characteristics

The evidence is current to July 2015. We found five trials assessing vigabatrin or carbamazepine monotherapy for newly diagnosed epilepsy, which recruited a total of 734 participants between six months and 65 years of age.

Key results

Results of this review show no significant differences between vigabatrin and carbamazepine in terms of time to treatment withdrawal and time to achieve six-month remission after dose stabilisation from randomisation, but they reveal some clinical disadvantage with vigabatrin on time to first seizure. Taking vigabatrin was more likely to result in weight gain. A safety concern was the high prevalence of visual field defects, as reported in a systematic review of observational studies (Maguire 2010).

Quality of the evidence

One study was assessed as good quality and the other four as poor quality.

Authors' conclusions: 

Data are currently insufficient to address the risk-benefit balance of VGB versus CBZ monotherapy for epilepsy. Given the high prevalence of visual field defects reported in an existing systematic review of observational studies (Maguire 2010), VGB monotherapy should be prescribed with caution for epilepsy and should not be considered a first-line choice. If necessary, the visual field should be frequently assessed. Future research should focus on investigating the reasons for visual field defects and exploring potential prevention strategies. Moreover, future monotherapy studies of epilepsy should report results according to the recommendations of the International League Against Epilepsy (ILAE) Commission, and methodological quality should be improved.

Read the full abstract...
Background: 

This is an update of a Cochrane review first published in 2012 (Cochrane Database of Systematic Reviews 2012, Issue 1).

The efficacy and safety of vigabatrin (VGB) as an add-on therapy for refractory epilepsy have been well established. However, this information needs to be weighed against the risk of development of visual field defects. Whether VGB monotherapy is an effective and safe treatment compared with the standard antiepileptic drug carbamazepine (CBZ) as monotherapy for epilepsy has not been systematically reviewed.

Objectives: 

To investigate the efficacy and safety of VGB versus CBZ monotherapy for epilepsy in children and adults.

Search strategy: 

For the latest update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2015, Issue 3 of 4), MEDLINE (1948 to July 2015), EMBASE (1974 to July 2015) and the Chinese Biomedical Database (CBM) (1979 to July 2015). We searched trial registers and contacted the manufacturer of VGB and authors of included studies for additional information. We applied no language restrictions.

Selection criteria: 

Randomised controlled trials (RCTs) comparing VGB versus CBZ monotherapy for epilepsy.

Data collection and analysis: 

Two review authors independently assessed trial quality and extracted data. The primary outcome was time to treatment withdrawal. Secondary outcomes were time to achieve six-month and 12-month remission after randomisation, time to first seizure after randomisation and adverse events. We presented results as hazard ratios (HRs) with 95% confidence intervals (CIs) (time to event data) or as risk ratios (RRs) with 95% CIs (adverse events).

Main results: 

Five studies involving a total of 734 participants were eligible for inclusion. We assessed only one study as good quality and the other four as 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 studies reported the same outcomes as those chosen for this review. No significant differences favoured 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, VGB was associated with more occurrences of weight gain and fewer occurrences of skin rash and drowsiness. No differences in visual field defects and visual disturbances were noted.

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