Posted by Iansf on March 3, 2005, at 11:11:25
Gabitril Off-Label Use Associated With Risk of New-Onset Seizures
Feb. 22, 2005 — The U.S. Food and Drug Administration (FDA) and Cephalon, Inc., have warned healthcare professionals and consumers of the risk of new-onset seizures and status epilepticus associated with the off-label use of tiagabine HCl (Gabitril), according to an alert sent today from MedWatch, the FDA's safety information and adverse event reporting program.Since the product's approval in 1997, the FDA has received 59 postmarketing reports of seizures associated with tiagabine use in patients with no prior history of epilepsy. More than 30 of these have occurred in patients prescribed tiagabine for off-label indications, such as psychiatric illness.
The FDA emphasizes that the safety and effectiveness of tiagabine have not been established for any indication other than adjunctive therapy for partial seizures in patients aged 12 years and older.
The seizures have typically occurred after initiation of tiagabine therapy or after dose increases, and have been associated with doses as low as 4 mg per day. Although most cases involved concomitant administration of drugs thought to lower the seizure threshold (antidepressants, antipsychotics, stimulants, or narcotics), the temporal relationship between tiagabine therapy initiation or dose increases and seizure incidence strongly suggests causality.
The FDA notes that dosing recommendations for tiagabine in the treatment of epilepsy are based on studies in which enzyme-inducing antiepileptic drugs (carbamazepine, phenytoin, primidone, and phenobarbital) were concomitantly administered, resulting in reduced plasma levels of tiagabine.
When administered as monotherapy, tiagabine plasma levels may be doubled. Because overdose has been linked to seizures and status epilepticus, the FDA recommends caution and dose titration in prescribing tiagabine for uninduced patients.
Tiagabine therapy should be discontinued in nonepileptic patients who develop seizures, and the possibility of an underlying seizure disorder should be evaluated.
More information concerning the use of tiagabine may be obtained by contacting Cephalon Professional Services at 1-800-896-5855.
The FDA notes that because MedWatch is a voluntary system, the actual incidence of tiagabine-associated adverse events may be greater than that reported. Healthcare providers are encouraged communicate these events to Cephalon, Inc., at the number above.
Alternatively, this information can be reported to the FDA's MedWatch program by phone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by returning a postage-paid FDA form 3500 by mail to 5600 Fishers Lane, Rockville, MD 20852-9787.
Reviewed by Gary D. Vogin, MD
poster:Iansf
thread:465935
URL: http://www.dr-bob.org/babble/20050227/msgs/465935.html