Tiagabine in clinical practice

Among the newly introduced antiepileptic drugs (AEDs), tiagabine (TGB) stands out as a compound with a well-understood and documented mechanism of action. It is a lipophilic derivative of nipecotic acid that blocks gamma -aminobutyric acid (GABA) reuptake by inhibition of the GAT-I transportation system, and that has no other significant pharmacodynamic effect. The relationship between intake and blood levels is linear. Usual daily maintenance doses range from 20 to 50 mg. It is completely absorbed by the gastrointestinal tract, and its half-life is similar to7-9 h. TGB is sensitive to enzyme induction: when coprescribed with enzyme-inducing AEDs, its half-life is shortened to 2-3 h, whereas the daily dosage has to be increased into the upper range. It should be given 3 times per day. Placebo-controlled, double-blind, add-on studies conducted in patients with drug-resistant focal epilepsies have demonstrated its efficacy and overall safety. The clinical benefits appear to persist over time. Data on its use in monotherapy are scanty. The efficacy and tolerability of TGB in the pediatric age still remain to be investigated adequately. In daily practice, TGB appears to be a safe drug, but mild to moderate side effects are frequently seen, especially during titration: these include dizziness and fatigue, and are clearly abated when the drug is absorbed during meals. Titration should be especially slow, no faster than 5 mg weekly. Clinicians also should beware of the possible occurrence of confusion, which may be misdiagnosed as absence status, a short-lasting, quickly reversible central nervous system-related side effect that appears to be correlated with the peak plasma concentrations of TGB. Particularly beneficial indications for TGB and/or AED associations including TGB have not been pointed out, but there is a hint that it works best in temporal lobe epilepsies.