A Cochrane review included 6 trials with a total of 948 subjects. Four parallel-group and two cross-over studies were included. The length of the treatment period was 7 weeks in the cross-over studies and 12 to 22 weeks in the parallel studies. The overall risk ratio (RR) for a 50% or greater reduction in seizure frequency (tiagabine vs placebo) was 3.16 (95% CI 1.97 to 5.07; 3 trials, n=769). Because of differences in response rates among trials, regression models were unable to provide reliable estimates of response to individual doses. The RR for treatment withdrawal was 1.81 (95% CI 1.25 to 2.62; 3 trials, n=769). The 99% CIs for the adverse effects of dizziness, fatigue, nervousness and tremor were significantly associated with tiagabine. For cognitive and quality of life outcomes, the limited available data suggested no significant effects.
Comment: The quality of evidence is downgraded by indirectness (short follow-up time).