Tiagabine dosage

The most important interactions of tiagabine involve induction of its metabolism by enzyme-inducing anticonvulsants (30). This results in larger tiagabine dosage requirements compared with patients taking monotherapy or valproic acid co-medication. 

EEG abnormalities Patients with a history of spike and wave discharges on EEG have been reported to have exacerbations of their EEG abnormalities associated with cognitive/neuropsychiatric events. In the documented cases of spike and wave discharges on EEG with cognitive/neuropsychiatric reactions, patients usually continued tiagabine, but required dosage adjustment. 

The effects of tiagabine have been studied in a 4-month, single-blind study in 52 children over the age of 2 years with different syndromes of refractory epilepsy (5). Adverse events, mostly mild to moderate, were reported by 39% of the children during the single-blind placebo period and by 83% of the children during tiagabine treatment. The events predominantly affected the nervous system weakness (19%), nervousness (19%), dizziness (17%), and somnolence (17%) were the most common. One child had hallucinations that responded to dosage reduction. Only three children withdrew because of adverse events. 

Tiagabine 0.45-40.57 mg/kg/day was associated with longstanding non-convulsive status epilepticus in three girls, two aged 12 years and one aged 17 years, with refractory localization-related epilepsy (17). Resolntion followed withdrawal of tiagabine or a reduction in dosage. 

Hepatic dysfunction is associated with impaired tiagabine elimination and can result in greater susceptibility to adverse effects (SEDA-21, 75). Tiagabine should only be used cautiously and in reduced dosages in these patients. 

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