Tiagabine administration

Generalized weakness Moderately severe to incapacitating generalized weakness has been reported following administration of tiagabine in approximately 1% of patients with epilepsy. The weakness resolved in all cases after a reduction in dose or discontinuation of tiagabine. 

Tiagabine is rapidly absorbed after oral administration, extensively bound to serum or plasma proteins, and metabolized mainly in the liver, predominantly by CYP3A. Its half-life of about 8 hours is shortened by 2 to 3 hours when coadministered with hepatic enzyme-inducing drugs such as phenobarbital, phenytoin, or carbamazepine. 

Phenobarbital, phenytoin, and valproic acid may increase the metabolism of carbamazepine by inducing CYP3A4 carbamazepine may enhance the biotransformation of phenytoin. Concurrent administration of carbamazepine may lower concentrations of valproic acid, lamotrigine, tiagabine, and topiramate. Carbamazepine reduces both the plasma concentration and therapeutic effect of haloperidol. The metabolism of carbamazepine may be inhibited by propoxyphene, erythromycin, cimetidine, fluoxetine, and isoniazid. 

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