Felbamate
Risk Factor: CM
Class: CENTRAL NERVOUS SYSTEM DRUGS
/ Anticonvulsants
Contents of this page:
Fetal Risk Summary
Breast Feeding Summary
References
Questions and Answers
Fetal Risk Summary
Little information on the effects in human pregnancy of the antiepileptic agent, felbamate, is available. The drug is structurally similar to meprobamate. Serious adult toxicity, including fatal cases of aplastic anemia and acute liver failure, has been recently (July and September 1994) reported by the manufacturer. One adverse pregnancy outcome, an infant with mental retardation whose mother was on monotherapy, has been reported to the Food and Drug Administration (F. Rosa, personal communication, FDA, 1994), but the relationship to the drug is unknown.
Citing information obtained from the manufacturer, one review stated that 10 women had become pregnant while enrolled in clinical trials of the drug and were subsequently dropped from the studies (1). Two of these women underwent elective termination of their pregnancies. A third patient was changed to phenytoin at 4 weeks' gestation and had a spontaneous abortion at 9.5 weeks. The remaining seven women eventually gave birth without any problems, but details on these pregnancies, whether felbamate or other anticonvulsants were continued throughout gestation, and the status of the newborns were not provided.
Felbamate was not teratogenic in rats and rabbits at doses up to 13.9 times and 4.2 times, respectively, the human daily dose on a mg/kg basis, or 3 times and <2 times, respectively, the human dose on a mg/m2 basis (2). In rats, however, there was a decrease in pup weight and an increase in pup deaths during lactation. The cause of the deaths was not known. The no-effect dose in rats was 6.9 times the human dose based on a mg/kg basis (1.5 times based on surface area) (2).
The drug crosses the placenta without accumulation in pregnant rats (2,3). Transplacental passage apparently has not been described in humans but should occur because of the low molecular weight (about 238).
Breast Feeding Summary
Felbamate is excreted into human milk (2). Although no reports have been located that describe the effects, if any, of exposure to this anticonvulsant via breast milk on human infants, both decreased weight and increased mortality were observed in rat pups of treated dams during lactation (2). The cause of the deaths was not known. Because of the potential for serious toxicity (e.g., aplastic anemia and acute liver failure) in a nursing infant, felbamate should be used cautiously, if at all, during lactation.
References
- Wagner ML. Felbamate: a new antiepileptic drug. Am J Hosp Pharm 1994;51:165766.
- Product information. Felbatol. Wallace Laboratories, 2000.
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Adusumalli VE, Yang JT, Wong KK, Kucharczyk N, Sofia RD. Felbamate pharmacokinetics in the rat, rabbit, and dog. Drug Metab Dispos Biol Fate Chem 1991;19:111625.
