FELL-ba-mate

Therapeutic Classification: anticonvulsants

• Used alone (monotherapy) or as adjunctive therapy with other anticonvulsants in treatment of partial seizures.
• Adjunctive therapy with other anticonvulsants in children (2–14 yr) who have partial or generalized seizures associated with Lennox-Gastaut syndrome.
• Because of deaths due to aplastic anemia and acute liver failure, felbamate should never be used as a first-line therapy, but should be reserved for patients whose epilepsy is so severe that these risks are considered acceptable given the drug's benefit.

• Probably acts by raising seizure threshold and preventing seizure spread.

• Decreased incidence of seizures.

Absorption: Well absorbed following oral administration.

Distribution: 0.7 L/kg.

Metabolism/Excretion: 40–50% excreted unchanged in urine; 40% metabolized by the liver.

Half-life: 20–23 hr.

(blood levels)

Contraindicated in:

• Hypersensitivity to felbamate or other carbamates (e.g. meprobamate)
• History of hepatic dysfunction
• History of blood dyscrasias.

Use Cautiously in:

• All patients (may ↑ risk of suicidal thoughts/behaviors)
• Renal dysfunction.

Derm: acne, rash.

EENT: diplopia, pharyngitis, rhinitis, sinusitis.

GI: anorexia, constipation, dyspepsia, nausea, vomiting, ACUTE LIVER FAILURE, altered taste, diarrhea, hiccups.

Hemat: APLASTIC ANEMIA.

MS: myalgia.

Neuro: dizziness, drowsiness, fatigue, headache, insomnia, psychological disturbances, anxiety, ataxia , SUICIDAL THOUGHTS.
Misc: flu-like syndrome, weight loss.

Drug-Drug:

• ↑blood levels and risk of toxicity from phenytoin,valproic acid, and phenobarbital.
• ↓carbamazepine blood levels but ↑ levels of carbamazepine epoxide, an active metabolite.
• Because of potential interactions, doses of carbamazepine, phenytoin, and valproic acid, and phenobarbital should be ↓ by 20–33% when initiating felbamate therapy. Further reductions may be required.
• Concurrent use of other hepatotoxic agents or drugs which may cause aplastic anemia may ↑ the risk of these serious adverse reactions.

Drug-Natural Products:

• See sedative interactions.
• St. John's wort may affect felbamate levels and effectiveness; avoid use.
• Concomitant use of kava-kava, valerian, skullcap, chamomile, or hops can ↑ CNS depression.

• PO (Adults and Children >14 yr): If used alone, start with 1200 mg/day in 3–4 divided doses. May be ↑ by 600 mg/day at 2-wk intervals up to a total of 3600 mg. If converting from other agents, start with 1200 mg/day in 3–4 divided doses and ↓ other anticonvulsants by 1/3. At wk 2, ↑ felbamate to 2400 mg/day in 3–4 divided doses and ↓ other anticonvulsants by up to 1/3 of their original dosage. At wk 3, ↑ felbamate to 3600 mg/day in 3–4 divided doses while continuing to ↓ doses of other anticonvulsants. If using as adjunctive therapy (with other agents), start with 1200 mg/day in 3–4 divided doses, ↓ doses of other anticonvulsants by 20%. ↑ dose at weekly intervals by 1200 mg/day to 3600 mg/day. ↓ doses of other anticonvulsants as necessary.
• PO (Children): As adjunctive therapy, start at 15 mg/kg/day in 3–4 divided doses, ↓ the dose of other anticonvulsants by 20%. ↑ dosage by 15 mg/kg/day (not to exceed 3600 mg/day) at weekly intervals to 45 mg/kg/day. ↓ doses of other anticonvulsants as necessary.

(Generic available)

• Tablets: 400 mg; 600 mg;
• Oral suspension: 600 mg/5 mL;

• Assess location, duration, and characteristics of seizure activity.
• Monitor closely for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.

• Monitor CBC with differential to determine baseline levels prior to and frequently during therapy. If ↓ in WBC, hemoglobin, hematocrit, or platelet count occurs, monitor closely and discontinue felbamate.
  • Monitor hepatic function prior to and frequently during therapy. May cause ↑ serum bilirubin, AST, and ALT levels. Discontinue felbamate immediately if any indication of liver injury develops.

• When used as adjunctive therapy with other anticonvulsants, monitor serum blood levels of other anticonvulsants throughout therapy.

• Implement seizure precautions. Obtain written, informed consent from patient before initiating therapy.
• PO: May be administered with food or antacids to minimize gastric irritation.
  • Shake oral suspension well before administering. Store at room temperature.

• Instruct patient to take felbamate as directed. Take missed doses as soon as possible but not just before next dose; do not double doses. Notify health care professional if more than 1 dose is missed. Medication should be gradually discontinued to prevent seizures and status epilepticus. Instruct patient to read the Medication Guide before starting and with each Rx refill, changes may occur.
• May cause dizziness and drowsiness. Advise patients to avoid driving or other activities requiring alertness until response to medication is known.
• Instruct patient that fever, sore throat, mouth ulcers, petechiae, unusual bleeding or bruising, abdominal pain, chills, pale stools, dark urine, or jaundice should be reported to health care professional immediately. Advise patient and family to notify health care professional if thoughts about suicide or dying, attempts to commit suicide; new or worse depression; new or worse anxiety; feeling very agitated or restless; panic attacks; trouble sleeping; new or worse irritability; acting aggressive; being angry or violent; acting on dangerous impulses; an extreme increase in activity and talking; other unusual changes in behavior or mood occur.
• Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking any other Rx, OTC, or herbal products. Advise patient not to take alcohol or other CNS depressants concurrently with this medication.
• Instruct patient to notify health care professional of medication regimen prior to treatment or surgery.
• Advise patient to use a nonhormonal form of contraception while taking felbamate.
• Advise patient to carry identification describing disease and medication regimen at all times.

• Absence or reduction of seizure activity.

Felbatol