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Felbatol Side Effects

Generic Name: felbamate

Note: This page contains information about the side effects of felbamate. Some of the dosage forms included on this document may not apply to the brand name Felbatol.

In Summary

Common side effects of Felbatol include: headache, nausea, vomiting, constipation, insomnia, and anorexia. Other side effects include: abdominal pain, abnormal gait, depression, diplopia, nervousness, tremor, and dysgeusia. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to felbamate: oral suspension, oral tablet

In addition to its needed effects, some unwanted effects may be caused by felbamate (the active ingredient contained in Felbatol). In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking felbamate:

More common:
  • Black, tarry stools
  • chest pain
  • chills
  • confusion
  • cough
  • delusions
  • dementia
  • depression
  • fever
  • loss of bladder control
  • painful or difficult urination
  • purple or red spots on the skin
  • shakiness in the legs, arms, hands, or feet
  • shortness of breath
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • trembling or shaking of the hands or feet
  • unusual bleeding or bruising
  • unusual tiredness or weakness
Less common:
  • Agitation, aggression, or other mood or mental changes
  • bladder pain
  • bloody or cloudy urine
  • bone pain
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • clumsiness or unsteadiness
  • frequent urge to urinate
  • loss of appetite
  • lower back or side pain
  • skin rash
  • swelling or puffiness of the face
  • trouble with breathing
  • unsteadiness, trembling, or other problems with muscle control or coordination
  • Continuing headache
  • continuing stomach pain
  • continuing vomiting
  • dark-colored urine
  • general feeling of tiredness or weakness
  • hives or itching
  • light-colored stools
  • muscle cramps
  • nasal congestion
  • nosebleeds or other unusual bruising or bleeding
  • pain
  • sensitivity of the skin to sunlight
  • swollen or painful glands
  • tightness in the chest
  • yellow eyes or skin

Minor Side Effects

Some of the side effects that can occur with felbamate may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Acid or sour stomach
  • bad, unusual, or unpleasant (after) taste
  • belching
  • body aches or pain
  • change in taste
  • change in walking and balance
  • constricted, pinpoint, or small pupils (black part of the eye)
  • crying
  • depersonalization
  • diarrhea
  • difficulty having a bowel movement (stool)
  • difficulty with sleeping
  • dizziness
  • double vision
  • dysphoria
  • ear congestion
  • euphoria
  • headache
  • heartburn
  • hiccup
  • indigestion
  • loss of appetite
  • loss of voice
  • nausea
  • paranoia
  • quick to react or overreact emotionally
  • rapidly changing moods
  • runny nose
  • seeing double
  • sleepiness or unusual drowsiness
  • sleeplessness
  • sneezing
  • stomach discomfort, upset, or pain
  • trouble sleeping
  • unable to sleep
  • weight loss
Less common:
  • Blemishes on the skin
  • blurred vision
  • decreased awareness or responsiveness
  • decreased weight
  • difficulty with moving
  • earache
  • hoarseness
  • joint pain
  • muscle aching or cramping
  • muscle pains or stiffness
  • pain or tenderness around the eyes and cheekbones
  • pimples
  • redness or swelling in the ear
  • severe sleepiness
  • swollen joints
  • tender, swollen glands in the neck
  • trouble with swallowing
  • voice changes

For Healthcare Professionals

Applies to felbamate: oral suspension, oral tablet

Nervous system

In controlled trials with felbamate (the active ingredient contained in Felbatol) 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 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 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 (the active ingredient contained in Felbatol) A case of massive acute hepatic necrosis and death within 40 days of initiation of felbamate therapy has also been reported.


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.[Ref]


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


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 (the active ingredient contained in Felbatol) to August 1, 1994.


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


Hypersensitivity side effects including a case of felbamate (the active ingredient contained in Felbatol) induced delayed anaphylaxis have been reported.


1. "Product Information. Felbamate (felbamate)." Amneal Pharmaceuticals, Glasgow, KY.

Not all side effects for Felbatol may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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