Felbamate
Felbamate (Felbatol)
( FELL-bah-mayt)
Pregnancy Category: C
Felbamate Felbatol (Rx)

Classification: Anticonvulsant, miscellaneous (second-line therapy)

See Also: See also Anticonvulsants .
NOTE: In August 1994 it was recommended that felbamate treatment be discontinued for epilepsy clients due to several cases of aplastic anemia. Revised labeling states, ``...Felbatol should only be used in patients whose epilepsy is so severe that the risk of aplastic anemia is deemed acceptable in light of the benefits conferred by its use...''

Action/Kinetics: Mechanism not known. Felbamate may reduce seizure spread and increase seizure threshold. Has weak inhibitory effects on both GABA and benzodiazepine receptor binding. Well absorbed after PO use. Terminal t 1/2: 20-23 hr. Trough blood levels are dose dependent. From 40% to 50% excreted unchanged in the urine.

Uses: Alone or as part of adjunctive therapy for the treatment of partial seizures with and without generalization in adults with epilepsy. As an adjunct in the treatment of partial and generalized seizures associated with Lennox-Gastaut syndrome in children. The drug should be used only as second-line therapy.

Contraindications: History of hepatic dysfunction or blood dyscrasia. Hypersensitivity to carbamates.

Special Concerns: Aplastic anemia and acute liver failure have been observed in a few clients. Use with caution during lactation. Safety and efficacy have not been established in children other than those with Lennox-Gastaut syndrome.

Side Effects: May differ depending on whether the drug is used as monotherapy or adjunctive therapy in adults or for Lennox-Gastaut syndrome in children. CNS: Insomnia, headache, anxiety, somnolence, dizziness, nervousness, tremor, abnormal gait, depression, paresthesia, ataxia, stupor, abnormal thinking, emotional lability, agitation, psychologic disturbance, aggressive reaction, hallucinations, euphoria, suicide attempt migraine. GI: Dyspepsia, vomiting, constipation, diarrhea, dry mouth, nausea, anorexia, abdominal pain, hiccoughs, esophagitis, increased appetite. Respiratory: Upper respiratory tract infection, rhinitis, sinusitis, pharyngitis, coughing. CV: Palpitation, tachycardia, SVT. Body as a whole: Fatigue, weight decrease or increase, facial edema, fever, chest pain, pain, asthenia, malaise, flu-like symptoms, anaphylaxis. Ophthalmologic: Miosis, diplopia, abnormal vision. GU: Urinary incontinence, intramenstrual bleeding, UTI. Hematologic: Aplastic anemia purpura, leukopenia, lymphadenopathy, leukocytosis, thrombocytopenia, granulocytopenia, positive antinuclear factor test, agranulocytosis qualitative platelet disorder. Dermatologic: Acne, rash, pruritus, urticaria, bullous eruption, buccal mucous membrane swelling, Stevens-Johnson syndrome. Miscellaneous: Otitis media, acute liver failure taste perversion, hypophosphatemia, myalgia, photosensitivity, substernal chest pain, dystonia, allergic reaction.

Laboratory Test Alterations: ALT, AST, gamma-glutamyl transpeptidase, LDH, alkaline phosphatase, CPK. Hypophosphatemia, hypokalemia, hyponatremia.

Drug Interactions: Carbamazepine / Carbamazepine steady-state levels and steady-state carbamazepine epoxide (metabolite) levels. Also, drug 50% in felbamate clearance Methsuximide / Normethsuxide levels; decrease methsuximide dose Phenobarbital / Phenobarbital plasma levels and in felbamate levels Phenytoin / Phenytoin steady-state drug levels necessitating a 40% decrease in drug dose. Also, drug felbamate clearance Valproic acid / Steady-state valproic acid levels

How Supplied: Suspension: 600 mg/5 mL; Tablet: 400 mg, 600 mg

Dosage
?Suspension, Tablets Monotherapy, initial therapy.
Adults over 14 years of age, initial: 1,200 mg/day in divided doses t.i.d.-q.i.d. The dose may be increased in 600-mg increments q 2 weeks to 2,400 mg/day based on clinical response and thereafter to 3,600 mg/day, if needed.
Conversion to monotherapy.
Adults: Initiate at 1,200 mg/day in divided doses t.i.d.-q.i.d. Reduce the dose of concomitant antiepileptic drugs by 1/3 at initiation of felbamate therapy. At week 2, the felbamate dose should be increased to 2,400 mg/day while reducing the dose of other antiepileptic drugs up to another 1/3 of the original dose. At week 3, increase the felbamate dose to 3,600 mg/day and continue to decrease the dose of other antiepileptic drugs as indicated by response.
Adjunctive therapy.
Adults: Add felbamate at a dose of 1,200 mg/day in divided doses t.i.d.-q.i.d. while reducing current antiepileptic drugs by 20%. Further decreases of concomitant antiepileptic drugs may be needed to minimize side effects due to drug interactions. The dose of felbamate can be increased by 1,200-mg/day increments at weekly intervals to 3,600 mg/day.
Lennox-Gastaut syndrome in children, aged 2-14 years.
As an adjunct, add felbamate at a dose of 15 mg/kg/day in divided doses t.i.d.-q.i.d. while decreasing present antiepileptic drugs by 20%. Further decreases in antiepileptic drug dosage may be needed to minimize side effects due to drug interactions. The dose of felbamate may be increased by 15-mg/kg/day increments at weekly intervals to 45 mg/kg/day.