By Akanksha, Pharmacology Correspondent, [RxPG] FDA and Cephalon, Inc. has warned healthcare professionals and the public of the risk of seizures in patients without epilepsy being treated with Gabitril(tiagabine).
From the launch of tiagabine in 1997 through December 31, 2004 there have been 59 postmarketing reports of seizures in patients without a history of epilepsy.
Clinicians are advised to carefully review the information mentioned below, which has been added to the tiagabine prescribing information.
Post-marketing reports have shown that tiagabine use has been associated with new onset seizures and status epilepticus in patients without epilepsy.
Dose may be an important predisposing factor in the development of seizures, although seizures have been reported in patients taking daily doses of tiagabine as low as 4 mg/day.
In most cases, patients were using concomitant medications (antidepressants, anti psychotics, stimulants, narcotics) that are thought to lower the seizure threshold. Some seizures occurred near the time of a dose increase, even after periods of prior stable dosing.
The tiagabine dosing recommendations in current labeling for treatment of epilepsy were based on use in patients with partial seizures 12 years of age and older, most of whom were taking enzyme-inducing antiepileptic drugs (AEDs; e.g., carbamazepine, phenytoin, primidone and phenobarbital) which lower plasma levels of tiagabine by inducing its metabolism. Use of tiagabine without enzyme-inducing antiepileptic drugs results in blood levels about twice those attained in the studies on which current dosing recommendations are based .
Safety and effectiveness of tiagabine have not been established for any indication other than as adjunctive therapy for partial seizures in adults and children 12 years and older.
In nonepileptic patients who develop seizures while on tiagabine treatment, tiagabine should be discontinued and patients should be evaluated for an underlying seizure disorder.
Seizures and status epilepticus are known to occur with tiagabine overdosage
Tiagabine is approved for use only as adjunctive therapy in adults and children 12 years and older in the treatment of partial seizures.
Because tiagabine has not been systematically evaluated in adequate and well-controlled clinical trials for any other indication, its safety and effectiveness have not been established for any other use. Cephalon does not recommend the use of tiagabine outside of its approved indication.
Dosing guidelines for tiagabine have been established only for its use as an adjunctive treatment for partial seizures and not for any other indication.
The current dosing guidelines for tiagabine have been established primarily for patients 12 years and older with partial epilepsy who are taking hepatic enzyme-inducing anticonvulsant drugs.
Patients who are not taking enzyme-inducing drugs would have systemic exposure to tiagabine that is higher than expected.
Thus, these patients require lower doses of tiagabine and may require a slower titration rate. Clinicians should exercise caution when prescribing tiagabine in uninduced patients.
Publication:
U.S. Food and Drug Administration (FDA)
On the web:FDA
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