Abstracts

RATIONALE: Concentric visual field defects (VFD) have been described in patients receiving vigabatrin (VGB). This study intended to investigate whether such concentric VFD might be associated with the use of tiagabine (TGB), an other GABAergic antiepileptic drug (AED).
METHODS: This study was an open, multicenter (Fi, UK, Nl, Au) cross-sectional study using matched controls receiving carbamazepine (CBZ) or lamotrigine (LTG), in patients newly diagnosed with partial epilepsy, receiving TGB monotherapy as first treatment (or similarly CBZ or LTG). Effects on visual fields (VF) were assessed using both Goldmann (primary endpoint: proportion of patients with a concentric VFD) and Humphrey perimetries. Visual charts were assessed on-site and then centralized and blinded with a randomization number ; each chart was then reviewed by a neuro-ophthalmologist expert blinded from both the treatment and the on-site ophtalmologist findings.
RESULTS: A total of 73 patients (TGB=35; CBZ=26; LTG=12) have been recruited ; 5 patients (TGB=3; CBZ=2) were later excluded because of pre-existing ophthalmological abnormalities that may interfer with visual examinations, or failure to comply with the monotherapy requirement, thus giving an eligible population of 68 patients (age range: 14-65 years; mean : 38.7 years). Mean duration of epilepsy was 5.9 years. Mean duration of TGB treatment was 27.8 months (range: 3-58 months ; 16 of the 32 patients were treated for more than 2 years). Mean daily TGB dose at inclusion was 15.8 mg (range 10-20mg). Mean duration of CBZ and LTG treatments were 25.8 and 27.2 months respectively. Mean daily dose at inclusion were 700 mg and 220.8 mg for CBZ and LTG respectively. Complete seizure control while under treatment for at least 3 months prior to inclusion was reached in 31 of the 32 TGB patients, 17 of the 24 CBZ patients and 8 of the 12 LTG patients.
None of the eligible patients in the TGB or CBZ groups had a concentric VFD as assessed by the on-site ophtalmologist, using the Goldmann perimetry. Concentric VFD in one eye was found in 2 patients in the LTG group; both patients presented with amblyopia (and esotropia in 1 case) which could have affected the VF assessment. None of the eligible patients had a concentric VFD when using Humphrey perimetry. Focal VFD were found using either perimetry in 2/32 TGB patients, 4/24 CBZ patients and 6/12 LTG patients. According to the expert, and taking into account the investigator[ssquote]s opinion, none of these VFD were of clinical relevance.
CONCLUSIONS: There was no clinically relevant VF abnormalities in TGB patients, nor in CBZ or LTG patients. None resembled those described with VGB and none were likely to be related to either TGB, CBZ or LTG.
Support: Sanofi-Synthelabo.
Disclosure: Honoraria - Sanofi-Synthelabo, Jansson-Cilag, Glaxo Smith Kline, UCB Pharma, Pfizer, Aventis, Novartis