Felbamate is not available in Canada, the UK, or Australia. It is available in some European countries using the name Taloxa marketed by Schering Plough. Felbatol is marketed in the United States by Medpointe Pharmaceuticals. The name or appearance may differ in other places.
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Before prescribing felbamate, the physician should be thoroughly familiar with the details of this prescribing information. Its chemical name is 2-phenyl-1,3-propanediol dicarbamate.
Felbamate is a white to off-white crystalline powder with a characteristic odor. It is very slightly soluble in water, slightly soluble in ethanol, sparingly soluble in methanol, and freely soluble in dimethyl sulfoxide. The molecular weight is The mechanism by which felbamate exerts its anticonvulsant activity is unknown, but in animal test systems designed to detect anticonvulsant activity, felbamate has properties in common with other marketed anticonvulsants.
Felbamate is effective in mice and rats in the maximal electroshock test, the subcutaneous pentylenetetrazol seizure test, and the subcutaneous picrotoxin seizure test. Felbamate also exhibits anticonvulsant activity against seizures induced by intracerebroventricular administration of glutamate in rats and N-methyl-D,L-aspartic acid in mice. Protection against maximal electroshock-induced seizures suggests that felbamate may reduce seizure spread, an effect possibly predictive of efficacy in generalized tonic-clonic or partial seizures.
Protection against pentylenetetrazol-induced seizures suggests that felbamate may increase seizure threshold, an effect considered to be predictive of potential efficacy in absence seizures. Receptor-binding studies in vitro indicate that felbamate has weak inhibitory effects on GABA-receptor binding, benzodiazepine receptor binding, and is devoid of activity at the MK receptor binding site of the NMDA receptor-ionophore complex.
However, felbamate does interact as an antagonist at the strychnine-insensitive glycine recognition site of the NMDA receptor-ionophore complex. Felbamate is not effective in protecting chick embryo retina tissue against the neurotoxic effects of the excitatory amino acid agonists NMDA, kainate, or quisqualate in vitro.
The monocarbamate and p-hydroxy metabolites had only weak 0. These metabolites did not contribute significantly to the anticonvulsant action of felbamate. Felbamate is well-absorbed after oral administration.
Absolute bioavailability oral vs. The suspension was shown to be bioequivalent to the capsule used in clinical trials, and pharmacokinetic parameters of the tablet and suspension are similar. The effect of food on absorption of the suspension has not been evaluated. Felbamate is excreted with a terminal half-life of 20 to 23 hours, which is unaltered after multiple doses.
Felbamate C max and AUC are proportionate to dose after single and multiple doses over a range of to mg single doses and to mg daily doses. C min trough blood levels are also dose proportional. The effects of felbamate kinetics on hepatic functional impairment have not been evaluated. Reduced felbamate clearance and a longer half-life were associated with diminishing renal function.
Cardiovascular: In adults, there is no effect of felbamate on blood pressure. Small but statistically significant mean increases in heart rate were seen during adjunctive therapy and monotherapy; however, these mean increases of up to 5 bpm were not clinically significant.
In children, no clinically relevant changes in blood pressure or heart rate were seen during adjunctive therapy or monotherapy with felbamate. Other Physiologic Effects: The only other change in vital signs was a mean decrease of approximately 1 respiration per minute in respiratory rate during adjunctive therapy in children.
In adults, statistically significant mean reductions in body weight were observed during felbamate monotherapy and adjunctive therapy. In children, there were mean decreases in body weight during adjunctive therapy and monotherapy; however, these mean changes were not statistically significant.
The results of controlled clinical trials established the efficacy of felbamate as monotherapy and adjunctive therapy in adults with partial-onset seizures with or without secondary generalization and in partial and generalized seizures associated with Lennox-Gastaut syndrome in children.
Both trials were conducted according to an identical study design. During a day baseline period, all patients had at least four partial-onset seizures per 28 days and were receiving one antiepileptic drug at a therapeutic level, the most common being carbamazepine.
In the multicenter trial, baseline seizure frequencies were In the single-center trial, baseline seizure frequencies were Patients were converted to monotherapy with felbamate or low-dose valproic acid during the first 28 days of the day treatment period.
Study endpoints were completion of study days or fulfilling an escape criterion. Criteria for escape relative to baseline were: 1 twofold increase in monthly seizure frequency, 2 twofold increase in highest 2-day seizure frequency, 3 single generalized tonic-clonic seizure GTC if none occurred during baseline, or 4 significant prolongation of GTCs. The primary efficacy variable was the number of patients in each treatment group who met escape criteria.
These two studies by design were intended to demonstrate the effectiveness of Felbamate monotherapy. The studies were not designed or intended to demonstrate comparative efficacy of the two drugs. For example, valproate was not used at the maximally effective dose. A double-blind, placebo-controlled crossover trial consisted of two week outpatient treatment periods. Among the 56 patients who completed the study, the baseline seizure frequency was 20 per month. Patients treated with felbamate had fewer seizures than patients treated with placebo for each treatment sequence.
The primary efficacy variable was time to fourth seizure after randomization to treatment with felbamate or placebo. The median times to fourth seizure were greater than 28 days in the felbamate group and 5 days in the placebo group.
Patients had a past history of using an average of eight antiepileptic drugs. The most commonly used antiepileptic drug during the baseline period was valproic acid.
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Felbamate Oral Suspension
Felbatol is the brand name used in the United States for felbamate. Felbamate is not available in Canada, the UK, or Australia. It is available in some European countries using the name Taloxa manufactured by Schering Plough. When Felbatol was introduced in , it carried high expectations. Many hoped it would be able to control seizure disorders that had not been controlled before. Unfortunately, after only 1 year the FDA recommended withdrawal of patients from Felbatol because of reports of very serious side effects aplastic anemia or liver failure.
Medically reviewed by Drugs. Last updated on Jan 10, This is not a list of all drugs or health problems that interact with felbamate oral suspension. Tell your doctor and pharmacist about all of your drugs prescription or OTC, natural products, vitamins and health problems. You must check to make sure that it is safe for you to take felbamate oral suspension with all of your drugs and health problems.