Immediate Suspension of Felbatol Therapy Advised

The US Food and Drug Administration has recommended "the immediate withdrawal of patients from therapy with Carter-Wallace's antiepilepsy drug Felbatol (felbamate)," because it has been linked to 10 cases of aplastic anemia (pancytopenia in the presence of bone marrow largely depleted of myeloid and erythroid precursors).

In a "Dear Doctor" letter to 240,000 physicians, Carter Wallace, in conjunction with the FDA, recommended immediate suspension of the therapy "unless in the physician's judgement an abrupt withdrawal would be deemed to pose a more serious risk to the patient."

The letter goes on to say that the reports of nine US cases of aplastic anemia in association with the use of felbamate occurred in no more than 100,000 or so patients, the majority of whom have been exposed for less than a year, which represents a great increase (50 fold or more) over the expected rate. The absolute rate may be higher than seen so far, says the company, because it is possible that either drug-induced aplastic anemia is typically delayed in onset, occurring weeks to months after initiation of treatment, or post-marketing surveillance typically captures only a fraction of incident causes.