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felbamate (Felbatol)
Tradename: Felbatol.
Indications:
1) monotherapy & adjunctive therapy in patients > 14 years of age with partial & secondary generalized seizures
2) adjunctive therapy in patients > 2 years of age with partial & generalized Lennox-Gastaut syndrome
3) reserve drug for patients with severe symptoms NOT responsive to other, less toxic agents
4) intractable seizures [4]
Contraindications:
- avoid in patients with liver failure [7]
Dosage:
1) Start 400 mg PO TID, max 3.6 g/day
2) Pediatrics: Start 15 mg/kg/day, max 45 mg/kg/day
3) do NOT discontinue abruptly
Tabs: 400 & 600 mg.
Suspension: 600 mg/5 mL.
Dosage adjustment in renal failure:
- yes
- supplemental dose after dialysis uncertain [7]
Monitor:
1) complete blood count (CBC) baseline, weekly during therapy & for 4 weeks after discontinuation [6]
2) liver function tests (LFTs)baseline & weekly
Adverse effects:
1) common (> 10%)
- nausea, anxiety, headache, fatigue, dizziness, diarrhea, anorexia, weight loss, vomiting, constipation, cough
2) less common (1-10%)
- drowsiness, insomnia, blurred or double vision, clumbsiness, weight gain, depression, behavioral changes, clouded sensorium, lethargy, muscle twitches, slurred speech, uncontrollable eye movements, acne, skin rash
3) uncommon (< 1%)
- alopecia, bleeding gums, gingival hyperplasia
4) other (serious)
a) aplastic anemia (marked increased incidence)
b) hepatotoxicity
Drug interactions:
1) felbamate increases levels of phenytoin, valproic acid
2) felbamate decreases carbamazepine level, but increases epoxide
3) phenytoin & carbamazepine decrease felbamate levels
Mechanism of action:
1) potentiates GABA receptor-linked Cl- channels
2) inhibits spontaneous discharges from voltage-dependent Na+ channels
3) inhibits NMDA receptors
4) inhibits AMPA receptors [5]
Interactions
drug interactions
drug adverse effects of anticonvulsants
monitor with anticonvulsants
General
anticonvulsant
Properties
MISC-INFO: elimination route KIDNEY
LIVER
1/2life 20-23 HOURS
protein-binding 25%
pregnancy-category C
safety in lactation -
Database Correlations
PUBCHEM cid=3331
References
- The Pharmacological Basis of Therapeutics, 9th ed.
Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- Harrison's Principles of Internal Medicine, 13th ed.
Companion Handbook. Isselbacher et al (eds),
McGraw-Hill Inc. NY, 1995, pg 702
- Kaiser Permanente Northern California Regional Drug
Formulary, 1998
- Department of Veterans Affairs, VA National Formulary
- restricted to neurology
- UpToDate 13.3
http://www.utdol.com
- Prescriber's Letter 17(7): 2010
Recommended Lab Monitoring for Common Medications
Liver Function Test Scheduling
Detail-Document#: 260704
(subscription needed) http://www.prescribersletter.com
- Medical Knowledge Self Assessment Program (MKSAP) 17,
American College of Physicians, Philadelphia 2015