Felbamate Side Effects

Some side effects of felbamate may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to felbamate: oral suspension, oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking felbamate: hives; fever; swollen glands; painful sores in or around your eyes or mouth; difficulty breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have any of these serious side effects:

• pale skin, weakness, easy bruising or bleeding (nosebleeds, bleeding gums);

• fever, chills, body aches, flu symptoms;

• fast or pounding heartbeats, feeling short of breath;

• nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

• pain or burning when you urinate;

• loss of balance or coordination; or

• worsening of seizures.

Less serious side effects of felbamate may include:

• dizziness, drowsiness, nervousness, tired feeling;

• headache;

• sleep problems (insomnia);

• changes in weight or appetite;

• acne, mild itching or skin rash;

• diarrhea, constipation, vomiting;

• runny or stuffy nose;

• blurred vision; or

• changes in your sense of taste.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to felbamate: oral suspension, oral tablet

Nervous system

In controlled trials with felbamate as monotherapy, no nervous system effect occurred with a frequency greater than 7%. However, the frequency of nervous system effects (particularly sedative effects) was much greater in controlled studies of felbamate as adjuvant therapy with other antiepileptic agents. Ataxia, tremor, involuntary movements, psychosis, and blurred vision have also been reported rarely.

One prospective investigation found 20 of 60 (33%) epileptic patients to have reported a headache. The headache was pounding in 11 patients, steady in 9 patients, and moderate or severe in 19 patients. Patients who had the headaches reported that they occurred at least once a week.

Nervous system side effects are common and include insomnia, headache, anxiety, dizziness, somnolence, fatigue, and lethargy.

Gastrointestinal

Gastrointestinal side effects are common and include nausea, vomiting, dyspepsia, constipation, diarrhea, and bad taste in mouth. Some clinicians have reported that anorexia and weight loss occur commonly.

Dyspepsia and vomiting occur in as many as 9% of treated patients.

Hepatic

Hepatic side effects include mild elevations of liver function tests which occur in as many as 5% of treated patients. The manufacturer reports that several cases of acute liver failure have also occurred in patients taking felbamate. A case of massive acute hepatic necrosis and death within 40 days of initiation of felbamate therapy has also been reported.

Dermatologic

Dermatologic side effects including rashes and acne occur in approximately 3% of treated patients. The Stevens-Johnson syndrome has been reported rarely. A case of toxic epidermal necrolysis has also been reported.

Metabolic

Metabolic side effects including hypophosphatemia have been reported in approximately 3% of treated patients.

Hematologic

Hematologic side effects include leukopenia, thrombocytopenia, and agranulocytosis rarely. Nine cases of aplastic anemia have been reported in the United States from the time of commercial release of felbamate to August 1, 1994.

Genitourinary

Genitourinary side effects including a case of urolithiasis have been reported.

Hypersensitivity

Hypersensitivity side effects including a case of felbamate induced delayed anaphylaxis have been reported.

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