Abstracts

RATIONALE: Vigabatrin (VGB), the first designer antiepileptic drug, was licensed in the UK in 1989. Since first described in 1997 it has become clear that it is associated with a significant risk of asymptomatic, irreversible retinopathy. Guidelines restricting it[scquote]s use have been published, but are these enough?
METHODS: This is a retrospective review of 560 patients prescribed VGB between 1989 and 2001 from a regional and satellite epilepsy clinic. Data is collected on dose and duration of treatment, results of quantitative perimetry and reasons for and outcome of discontinuation.
RESULTS: In the first 500 patients analysed, the visual fields were abnormal with no alternative cause in 34 of the 79 tested (43%). There was no clear relationship between dose of VGB or length of treatment and the occurrence of a visual field abnormality. 45 patients continue on VGB, and a further 66 have been lost to follow up whilst taking VGB. 56 patients had stopped VGB due to a visual field abnormality or concern over this potential adverse effect. In this group the seizure control was no different or improved in 46 (82%) whilst only 4 (7%) deteriorated.
CONCLUSIONS: This study confirms the previously reported high incidence of visual field defects associated with VGB.The drug was widely prescribed and many patients may not have been appropriately counseled.
There are significant cost implications in adherence to the guidelines on the use of VGB, and in tracing/ assessing those patients lost to follow-up. Given that switch over rarely results in deterioration in seizure control, there is a good case for cessation of VGB in most individuals. However, in clinical practice an individual risk/benefit ratio needs to be taken into consideration.
Support: Janssen-Cilag