Background: Epilepsy is a common neurological condition, affecting almost 0.5 to 1% of the population. Nearly 30% of people with epilepsy are resistant to currently available drugs. Tiagabine is one of the newer antiepileptic drugs and its effects as an adjunct (add-on) to standard drugs are assessed in this review.
Objectives: To evaluate the effects of add-on treatment with tiagabine upon seizures, adverse effects, cognition and quality of life for people with drug-resistant localisation related seizures.
Search methods: This is an updated version of the original Cochrane review published in issue 10, 2010. We searched the Cochrane Epilepsy Group's Specialised Register (December 2011), the Cochrane Central Register of Controlled Trials (CENTRAL, issue 4, 2011 of The Cochrane Library), and MEDLINE (1948 to November 2011). No language restrictions were imposed. We also contacted the manufacturers of tiagabine and experts in the field to seek any ongoing or unpublished studies.
Selection criteria: Randomised placebo controlled add-on trials of people of any age with localisation related seizures, in which an adequate method of concealment of randomisation was used were included. The studies could be double, single or unblinded and be of parallel or crossover design. They had to have a minimum treatment period of eight weeks. Trials using an active drug control group were also included.
Data collection and analysis: Two review authors independently selected trials for inclusion and extracted data. Any disagreements were resolved by discussion. Outcomes investigated included 50% or greater reduction in seizure frequency; treatment withdrawal; adverse effects; effects on cognition and quality of life. The primary analyses were by intention-to-treat. Worst case and best case analyses were also calculated for seizure outcomes. Dose response was evaluated in regression models.
Main results: Four parallel group and two crossover group trials were included. The overall relative risk (RR) with 95% confidence intervals (CIs) for a 50% or greater reduction in seizure frequency (tiagabine versus placebo) was 3.16 (95% CI 1.97 to 5.07). Due to differences in response rates among trials, regression models were unable to provide reliable estimates of responses to individual doses. The RR for treatment withdrawal was 1.81 (95% CI 1.25 to 2.62). The 99% CIs for the following adverse effects: dizziness; fatigue; nervousness and tremor did not include unity, indicating that they are significantly associated with tiagabine. For cognitive and quality of life outcomes the limited data available suggested that there were no significant effects on cognition and mood and adjustment.
Authors' conclusions: Tiagabine reduces seizure frequency but is associated with some adverse effects when used as an add-on for people with drug-resistant localisation-related seizures.