Felbamate Side Effects

Medically reviewed by Drugs.com. Last updated on Mar 17, 2025.

Applies to felbamate: oral suspension, oral tablet.

Precautions

It is very important that your doctor check the progress of you or your child at regular visits. This is necessary to allow dose adjustments and to check for serious unwanted effects.

It is important to tell your doctor if you become pregnant. Your doctor may want you to join the North American Antiepileptic Drug Pregnancy Registry, which is used by pregnant patients who are taking this medicine.

Felbamate has caused a few cases of a serious blood disorder called aplastic anemia and a few cases of liver failure. Talk to your doctor about these risks.

Stop using this medicine and check with your doctor right away if you or your child have pain or tenderness in the upper stomach; pale stools; dark urine; loss of appetite; nausea; unusual tiredness or weakness; or yellow eyes or skin. These could be symptoms of a serious liver problem.

Tell your doctor right away if you or your child has chest pain; chills; cough; fever; headache; shortness of breath; sores, ulcers, or white spots on lips or in mouth; swollen or painful glands; tightness in chest; unusual bleeding or bruising; unusual tiredness or weakness; or wheezing. These could be symptoms of aplastic anemia.

Do not stop taking felbamate without first checking with your doctor. Your doctor may want you to gradually reduce the amount you or your child are taking before stopping completely. Stopping the medicine suddenly may cause your seizures to return or to occur more often.

If you or your child develop any unusual or strange thoughts and behavior while taking this medicine, be sure to discuss it with your doctor. Other changes might be confusion, worsening of depression, hallucinations (seeing, hearing, or feeling things that are not there), suicidal thoughts, and unusual excitement, nervousness, or irritability.

Felbamate may cause blurred vision, double vision, or other changes in vision. It may also cause some people to become dizzy or drowsy. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert or able to see well. If these reactions are especially bothersome, check with your doctor.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of felbamate

Along with its needed effects, felbamate may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking felbamate:

Other side effects of felbamate

Some side effects of felbamate may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to felbamate: oral suspension, oral tablet.

Nervous system adverse events

• Very common (10% or more): Headache (36.8%), somnolence (19.3%), dizziness (18.4%)
• Common (1% to 10%): Tremor, abnormal gait, paresthesia, ataxia
• Uncommon (0.1% to 1%): Migraine
• Postmarketing reports: Hyperpyrexia, paralysis, mononeuritis^[Ref]

Gastrointestinal

• Very common (10% or more): Nausea (34.2%), vomiting (16.7%), dyspepsia (12.3%), constipation (11.4%)
• Common (1% to 10%): Diarrhea, dry mouth, abdominal pain, hiccough
• Uncommon (0.1% to 1%): Esophagitis
• Postmarketing reports: GI hemorrhage, pancreatitis, hematemesis, gastritis, rectal hemorrhage, flatulence, gingival bleeding, acquired megacolon, ileus, intestinal obstruction, enteritis, ulcerative stomatitis, glossitis, dysphagia, jaundice, gastric ulcer, gastric dilatation, gastroesophageal reflux^[Ref]

Hepatic

• Common (1% to 10%): Serum glutamic-pyruvic transaminase (SGPT) increased
• Postmarketing reports: Hepatitis, hepatic failure, hepatorenal syndrome^[Ref]

Dermatologic

• Common (1% to 10%): Acne, rash, pruritus
• Uncommon (0.1% to 1%): Urticaria, bullous eruption
• Rare (less than 0.1%): Buccal mucous membrane swelling, Stevens-Johnson Syndrome, photosensitivity
• Postmarketing reports: Abnormal body odor, sweating, lichen planus, livedo reticularis, alopecia, toxic epidermal necrolysis (TEN)^[Ref]

Metabolic

• Very common (10% or more): Anorexia (19.3%)
• Common (1% to 10%): Weight loss, weight gain, hypophosphatemia
• Uncommon (0.1% to 1%): Increased appetite, hypokalemia, hyponatremia, LDH increased, alkaline phosphatase increased
• Rare (less than 0.1%): Creatinine phosphokinase increased
• Postmarketing reports: Hyperammonemia, hypernatremia, hypoglycemia, SIADH, hypomagnesemia, dehydration, hyperglycemia, hypocalcemia^[Ref]

Hematologic

• Very common (10% or more): Purpura (12.9%)
• Common (1% to 10%): Leukopenia
• Uncommon (0.1% to 1%): Leukocytosis, thrombocytopenia, granulocytopenia
• Rare (less than 0.1%): Antinuclear factor test positive, qualitative platelet disorder, agranulocytosis
• Postmarketing reports: Sepsis, increased and decreased prothrombin time, anemia, hypochromic anemia, aplastic anemia, pancytopenia, hemolytic uremic syndrome, increased mean corpuscular volume with and without anemia, coagulation disorder, embolism-limb, disseminated intravascular coagulation, eosinophilia, hemolytic anemia, leukemia, including myelogenous leukemia, and lymphoma, including T-cell and B-cell lymphoproliferative disorders^[Ref]

Genitourinary

• Common (1% to 10%): Intramenstrual bleeding, urinary tract infection, urinary incontinence
• Frequency not reported: Menstrual disorder, hematuria, urinary retention, vaginal hemorrhage, dysuria^[Ref]

Hypersensitivity

• Rare (less than 0.1%): Anaphylactoid reaction^[Ref]

Cardiovascular

• Common (1% to 10%): Palpitation, tachycardia
• Uncommon (0.1% to 1%): Lymphadenopathy
• Rare (less than 0.1%): Supraventricular tachycardia
• Postmarketing reports: Atrial fibrillation, atrial arrhythmia, cardiac arrest, torsade de pointes, cardiac failure, hypotension, hypertension, flushing, thrombophlebitis, ischemic necrosis, gangrene, peripheral ischemia, bradycardia, Henoch-Schonlein purpura (vasculitis), cerebrovascular disorder, cerebral edema^[Ref]

Immunologic

• Common (1% to 10%): Influenza-like symptoms
• Postmarketing reports: Lupus syndrome^[Ref]

Musculoskeletal

• Common (1% to 10%): Myalgia
• Uncommon (0.1% to 1%): Dystonia
• Postmarketing reports: Rigors, arthralgia, muscle weakness, involuntary muscle contraction, rhabdomyolysis^[Ref]

Ocular

• Common (1% to 10%): Diplopia, abnormal vision, miosis
• Postmarketing reports: Nystagmus, hemianopsia, conjunctivitis^[Ref]

Oncologic

• Postmarketing reports: Neoplasm^[Ref]

Other

• Very common (10% or more): Fever (22.6%), fatigue (16.8%)
• Common (1% to 10%): Otitis media, face edema, depression, taste perversion, pain, asthenia, malaise
• Postmarketing reports: Edema, sudden death, hypothermia, fetal death, microcephaly, genital malformation, anencephaly, encephalocele, decreased hearing, placental disorder^[Ref]

Psychiatric

• Very common (10% or more): Insomnia (17.5%)
• Common (1% to 10%): Anxiety, nervousness, stupor, abnormal thinking, emotional lability, agitation, psychological disturbance, aggressive reaction
• Uncommon (0.1% to 1%): Hallucination, euphoria, suicide attempt
• Postmarketing reports: Delusion, manic reaction, paranoid reaction, confusion, psychosis, apathy, impaired concentration^[Ref]

Renal

• Postmarketing reports: Acute renal failure, nephrosis, abnormal renal function^[Ref]

Respiratory

• Common (1% to 10%): Upper respiratory tract infection, rhinitis, chest pain, sinusitis, pharyngitis, coughing
• Postmarketing reports: Respiratory depression^[Ref]

See also:

Further information

Felbamate side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

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