Felbatol (felbamate)
Last reviewed · Source: First Databank (FDB) drug data
Overview
Felbamate, a dicarbamate, is an anticonvulsant.
Felbamate, a dicarbamate, is an anticonvulsant agent. Felbamate is structurally related to but pharmacologically distinct from meprobamate. Felbamate has a unique spectrum of activity compared with other currently available anticonvulsants.
The exact mechanism of action of felbamate is not known, but available data suggest that the drug increases seizure threshold and reduces seizure spread. A predominant effect on any particular cell process has not been demonstrated to date, but felbamate appears to exhibit a spectrum of anticonvulsant activity that is pharmacologically distinct from other currently available agents. In animals, felbamate protects against seizures induced by electrical stimulation, suggesting that it would be effective in the management of tonic-clonic (grand mal) seizures and partial seizures.
In animals, felbamate also protects against seizures induced by pentylenetetrazol, indicating that it may be effective in the management of absence (petit mal) seizures. Felbamate also protects against seizures in animals induced by picrotoxin, glutamate, or N-methyl-d,l-aspartic acid; it does not protect against seizures induced by bicuculline or strychnine.
In vitro studies indicate that felbamate has weak inhibitory effects on binding at gamma-aminobutyric acid (GABA) receptors and benzodiazepine receptors. The monocarbamate, p-hydroxy, and 2-hydroxy metabolites of felbamate appear to contribute little, if any, to the anticonvulsant action of the drug.
SumMon(R) (see Users Guide). For additional information on this drug until a more detailed monograph is developed and published, the manufacturer's labeling should be consulted. It is essential that the labeling be consulted for detailed information on the usual cautions, precautions, and contraindications concerning potential drug interactions and/or laboratory test interferences and for information on acute toxicity.
In July 1993, felbamate (Felbatol(R)) originally was approved by the FDA for use as monotherapy or in combination with other anticonvulsant agents in the management of partial seizures with or without secondary generalization in adults. Felbamate also was approved by FDA at that time for use in combination with other anticonvulsant agents in the management of partial and generalized seizures associated with Lennox-Gastaut syndrome in children and has been designated an orphan drug by FDA for the treatment of this latter syndrome. However, because felbamate has since been associated with marked increases in the incidences of aplastic anemia and acute hepatic failure, the drug is currently reserved for use only in patients who have not responded adequately to alternative safer treatments and whose seizure disorder is so severe that the risks of the drug are considered acceptable in light of the potential benefits.
Decisions about the potential benefits and risks of felbamate therapy generally should be made in consultation with appropriate hematologic and hepatic disease experts. (See Cautions.)
Generic name: felbamate
Pronunciation: (fel-BAM-ate)
Reference product & biosimilars
No reference, biosimilar or interchangeable associated with this drug.
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Indications
The following indications are listed for Felbatol:
- Complex-Partial Epilepsy
- Lennox-Gastaut Epilepsy
- Partial Epilepsy Treatment Adjunct
- Simple-Partial Epilepsy
Also known as: Automatic Epilepsy, Complex Focal Epilepsy, Complex Focal Seizures, Complex Local Seizures, Complex Partial Epilepsy, Complex Partial Seizures, Complex Psychomotor Epilepsy, Complex Psychomotor Seizure, Complex Temporal Lobe Epilepsy, Complex Temporal Lobe Seizures, Elementary Focal Seizures, Elementary Partial Seizures, Epilepsy Of Lennox Gastaut Syndrome, Partial Onset Seizures Treatment Adjunct, Partial Seizures Treatment Adjunct, Psychic Epilepsy, Psychomotor Epilepsy, Psychomotor Seizure, Simple Focal Epilepsy, Simple Focal Seizures, Simple Local Seizures, Simple Partial Epilepsy, Simple Psychomotor Epilepsy, Simple Psychomotor Seizures, Simple Temporal Lobe Epilepsy, Simple Temporal Lobe Seizures, Temporal Lobe Epilepsy, Temporal Lobe Seizure.
Dosing
Dosage of felbamate must be carefully and slowly adjusted according to individual requirements and response. Felbamate should be withdrawn slowly because abrupt discontinuance of the drug may precipitate seizures. (See Cautions: Precautions and Contraindications.)
When felbamate is used as initial monotherapy, therapy should begin with a low dosage of the drug and slowly increased. When felbamate is added to an existing anticonvulsant regimen, the drug should be added gradually while dosage of the other anticonvulsant(s) is decreased to reduce the risk of adverse effects from drug interactions. When transferring patients from combination therapy to monotherapy with felbamate, dosage of felbamate should be increased gradually while dosages of other anticonvulsant agents should be decreased gradually and discontinued.
The initial dosage of felbamate as monotherapy or adjunctive therapy (i.e., in combination with other anticonvulsants) for the management of partial seizures in adults and adolescents 14 years of age or older is 1.2 g daily administered in 3 or 4 divided doses. Subsequent dosage may be increased gradually based on clinical response; recommended titration increments and schedules are based on whether the patient is receiving felbamate as initial monotherapy or adjunctive therapy, or converting from combination therapy to felbamate monotherapy. The majority of patients in both monotherapy and adjunctive trials received a felbamate dosage of 3.6 g daily. More rapid titration of felbamate dosage than that currently suggested by the manufacturer occasionally has been employed.
For patients with partial seizures receiving felbamate as initial monotherapy, the initial felbamate dosage may be increased by 600-mg daily increments at 2-week intervals to 2.4 g daily administered in 3 or 4 divided doses or until optimum clinical response is obtained. Clinicians are advised to titrate previously untreated patients under close medical supervision. If adequate seizure control has not been achieved and further increases in monotherapy dosage are considered clinically necessary, felbamate dosage may be titrated further to 3.6 g daily. Felbamate has not been evaluated systematically as initial monotherapy.
For patients with partial seizures converting from combination therapy to felbamate monotherapy, the initial felbamate dosage may be increased by 1.2-g daily increments at weekly intervals up to 3.6 g daily administered in 3 or 4 divided doses. As felbamate replaces the existing anticonvulsant regimen, dosage(s) of the other anticonvulsant(s) should be gradually reduced (by 33% of the baseline dosage in the first week, then an additional 33% or less of the baseline dosage in the second week, and then as clinically indicated in the third week) and discontinued.
For patients with partial seizures receiving felbamate as adjunctive therapy with other anticonvulsant agents (e.g., phenytoin, valproic acid, phenobarbital, carbamazepine), the initial felbamate dosage may be increased by 1.2-g daily increments at weekly intervals up to 3.6 g daily administered in 3 or 4 divided doses. Dosage(s) of the other anticonvulsant(s) must be reduced initially by at least 20%; further reductions in dosage(s) of concomitant anticonvulsant(s) may be necessary to avoid adverse effects caused by drug interactions.
The usual initial dosage of felbamate as adjunctive therapy for the management of Lennox-Gastaut syndrome in children 2-14 years of age is 15 mg/kg daily administered in 3 or 4 divided doses. Dosage may be increased by 15 mg/kg daily at weekly intervals to 45 mg/kg daily administered in 3 or 4 divided doses. As felbamate is added to existing anticonvulsants (e.g., phenytoin, valproic acid, phenobarbital, carbamazepine), the dosage(s) of the other anticonvulsant(s) must be decreased initially by at least 20%; further reductions in dosage(s) of concomitant anticonvulsant(s) may be necessary to avoid adverse effects caused by drug interactions.
If felbamate is used in geriatric patients, the initial dosage usually should be at the low end of the dosage range. (See Cautions: Geriatric Precautions.)
The manufacturer states that initial and maintenance dosages of felbamate should be reduced by 50% in patients with renal impairment. Adjunctive therapy with drugs that affect plasma felbamate concentrations, especially other anticonvulsants, may warrant further reductions in felbamate daily dosage in patients with renal impairment.
Felbamate should not be used in patients with hepatic impairment.
Felbamate is administered orally (as tablets or oral suspension). The manufacturer states that both the commercially available tablet and oral suspension have been shown to be bioequivalent to the capsule formulation used in clinical trials; the pharmacokinetic profiles of the tablet and oral suspension are similar. Food does not appear to affect absorption of felbamate tablets; the effect of food on absorption of the oral suspension has not been evaluated.
Patients who are currently receiving or beginning therapy with felbamate and/or any other anticonvulsant for any indication should be closely monitored for the emergence or worsening of depression, suicidal thoughts or behavior (suicidality), and/or any unusual changes in mood or behavior. (See Cautions: Nervous System Effects and see Cautions: Precautions and Contraindications.)
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Drug interactions
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Contraindications
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There are no contraindication contraindications for this drug.
There are no severe contraindications for this drug.
There are no moderate contraindications for this drug.
Adverse reactions
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There are no severe adverse reactions for this drug.
There are no less severe adverse reactions for this drug.
Precautions
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Reproduction studies in rats and rabbits receiving felbamate doses of up to 13.9 and 4.2 times, respectively, the human daily dose of the drug on mg/kg basis (3 and less than 2 times, respectively, the human daily dose on a mg/m2 basis) did not reveal evidence of teratogenicity; however, in rats, there was a decrease in pup weight and an increase in pup deaths during lactation. The cause of these deaths is not known. The dose at which there was no effect on rat pup mortality was 6.9 times the human dose on a mg/kg basis (1.5 times the human dose on a mg/m2 basis). Felbamate crosses the placenta in rats. There are, however, no adequate and controlled studies to date using the drug in pregnant women, and the effect of felbamate on labor and delivery in humans also is not known. Felbamate should be used during pregnancy only when clearly needed.
Women who are pregnant while receiving felbamate should be encouraged to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry at 888-233-2334; registry information also is available at http://www.aedpregnancyregistry.org.
Felbamate is distributed into milk. Since the potential effect in nursing infants is not known, some clinicians state that felbamate probably should not be used during breast-feeding.
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ICD codes
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Formulary status
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Last reviewed · Source: First Databank (FDB) drug data
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