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Fanatrex Side Effects

Generic Name: gabapentin

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

For the Consumer

Applies to gabapentin: oral capsule, oral solution, oral suspension, oral tablet

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

Severity: Major

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

More common:
  • Clumsiness or unsteadiness
  • continuous, uncontrolled, back-and-forth, or rolling eye movements
More common in children
  • Aggressive behavior or other behavior problems
  • anxiety
  • concentration problems and change in school performance
  • crying
  • depression
  • false sense of well-being
  • hyperactivity or increase in body movements
  • rapidly changing moods
  • reacting too quickly, too emotional, or overreacting
  • restlessness
  • suspiciousness or distrust
Less common:
  • Black, tarry stools
  • chest pain
  • chills
  • cough
  • depression, irritability, or other mood or mental changes
  • fever
  • loss of memory
  • pain or swelling in the arms or legs
  • painful or difficult urination
  • shortness of breath
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • unusual bleeding or bruising
  • unusual tiredness or weakness
Incidence not known:
  • Abdominal or stomach pain
  • blistering, peeling, or loosening of the skin
  • clay-colored stools
  • coma
  • confusion
  • convulsions
  • dark urine
  • decreased urine output
  • diarrhea
  • dizziness
  • fast or irregular heartbeat
  • headache
  • increased thirst
  • itching or skin rash
  • joint pain
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • loss of appetite
  • muscle ache or pain
  • nausea
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • unpleasant breath odor
  • vomiting of blood
  • yellow eyes or skin

Severity: Minor

Some of the side effects that can occur with gabapentin 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:
  • Blurred vision
  • cold or flu-like symptoms
  • delusions
  • dementia
  • hoarseness
  • lack or loss of strength
  • lower back or side pain
  • swelling of the hands, feet, or lower legs
  • trembling or shaking
Less common or rare:
  • Accidental injury
  • appetite increased
  • back pain
  • bloated or full feeling
  • body aches or pain
  • burning, dry, or itching eyes
  • change in vision
  • change in walking and balance
  • clumsiness or unsteadiness
  • congestion
  • constipation
  • cough producing mucus
  • decrease in sexual desire or ability
  • difficulty with breathing
  • dryness of the mouth or throat
  • earache
  • excess air or gas in the stomach or intestines
  • excessive tearing
  • eye discharge
  • feeling faint, dizzy, or lightheadedness
  • feeling of warmth or heat
  • flushed, dry skin
  • flushing or redness of the skin, especially on the face and neck
  • frequent urination
  • fruit-like breath odor
  • impaired vision
  • incoordination
  • increased hunger
  • increased sensitivity to pain
  • increased sensitivity to touch
  • increased thirst
  • indigestion
  • noise in the ears
  • pain, redness, rash, swelling, or bleeding where the skin is rubbed off
  • passing gas
  • redness or swelling in the ear
  • redness, pain, swelling of the eye, eyelid, or inner lining of the eyelid
  • runny nose
  • sneezing
  • sweating
  • tender, swollen glands in the neck
  • tightness in the chest
  • tingling in the hands and feet
  • trouble sleeping
  • trouble swallowing
  • trouble thinking
  • twitching
  • unexplained weight loss
  • voice changes
  • vomiting
  • weakness or loss of strength
  • weight gain

For Healthcare Professionals

Applies to gabapentin: compounding powder, oral capsule, oral solution, oral tablet, oral tablet extended release

Nervous system

Nervous system side effects have been common. Somnolence, dizziness, ataxia, headache, and fatigue have been reported to occur in more than 10% of treated patients. Vertigo, hyperkinesia, paresthesia, decreased or absent reflexes, increased reflexes, anxiety, and hostility have been reported frequently. CNS tumors, syncope, dreaming abnormal, aphasia, hypesthesia, intracranial hemorrhage, hypotonia, dysesthesia, paresis, dystonia, hemiplegia, facial paralysis, stupor, cerebellar dysfunction, positive Babinski sign, decreased position sense, subdural hematoma, apathy, hallucination, decrease or loss of libido, agitation, paranoia, depersonalization, euphoria, feeling high, doped-up sensation, suicide attempt, and psychosis have been reported infrequently. Choreoathetosis, orofacial dyskinesia, encephalopathy, nerve palsy, personality disorder, increased libido, subdued temperament, apraxia, fine motor control disorder, meningismus, local myoclonus, hyperesthesia, hypokinesia, mania, neurosis, hysteria, antisocial reaction, and suicide have been reported rarely. Nystagmus, tremor, nervousness, amnesia, dysarthria and depression have also been reported. A small number of cases of absence status and status epilepticus have occurred in patients taking gabapentin (the active ingredient contained in Fanatrex) Cases of delirium tremens have been reported upon gabapentin withdrawal.[Ref]


Gastrointestinal side effects have been reported in one to three percent of treated patients. Anorexia, flatulence, and gingivitis have been reported frequently. Glossitis, gum hemorrhage, thirst, stomatitis, increased salivation, gastroenteritis, hemorrhoids, bloody stools, and fecal incontinence have been reported infrequently. Dysphagia, eructation, pancreatitis, peptic ulcer, colitis, blisters in mouth, tooth discoloration, salivary gland enlarged, lip hemorrhage, esophagitis, hiatal hernia, hematemesis, proctitis, irritable bowel syndrome, rectal hemorrhage, and esophageal spasm have been reported rarely. Dyspepsia, dry mouth, constipation, dental abnormalities, flatulence, increased appetite, breast enlargement, and weight gain have also been reported.[Ref]


Other side effects have been reported to include withdrawal effects. Withdrawal of gabapentin (the active ingredient contained in Fanatrex) therapy has been reported to cause the following effects in less than 2% of treated patients: somnolence, ataxia, fatigue, nausea, vomiting, and dizziness.

Hearing loss, earache, tinnitus, inner ear infection, otitis, taste loss, unusual taste, ear fullness, perforated ear drum, sensitivity to noise, eustachian tube dysfunction, otitis externa, odd smell, and labyrinthitis have also been reported.

Other side effects reported postmarketing have included angioedema, blood glucose fluctuation, breast enlargement, elevated creatine kinase, elevated liver function tests, erythema multiforme, fever, hyponatremia, jaundice, movement disorder, and Stevens-Johnson syndrome.[Ref]


Hematologic side effects have frequently been reported to include purpura. Anemia, thrombocytopenia, and lymphadenopathy have been reported infrequently. Increased WBC count, lymphocytosis, non-Hodgkin's lymphoma, and increased bleeding time have been reported rarely. Isolated cases of decreased white blood cell counts have also been reported.[Ref]

The patients reported to have decreased white blood cell counts were also taking carbamazepine.[Ref]


Cardiovascular side effects including hypertension have been reported to occur in more than one percent of patients taking gabapentin (the active ingredient contained in Fanatrex) Hypotension, angina pectoris, peripheral vascular disorder, palpitation, tachycardia, and murmur have been reported infrequently. Atrial fibrillation, heart failure, thrombophlebitis, deep thrombophlebitis, myocardial infarction, cerebrovascular accident, pulmonary thrombosis, ventricular extrasystoles, bradycardia, premature atrial contraction, pericardial rub, heart block, pulmonary embolus, hyperlipidemia, hypercholesterolemia, pericardial effusion, and pericarditis have been reported rarely. A case of gabapentin induced edema has also been reported.[Ref]


Ocular side effects including abnormal vision have been reported frequently. Cataract, conjunctivitis, dry eyes, eye pain, visual field defect, photophobia, bilateral or unilateral ptosis, eye hemorrhage, hordeolum, eye twitching, diplopia and blurred vision have been reported infrequently. Eye itching, abnormal accommodation, eye focusing problem, watery eyes, retinopathy, glaucoma, iritis, corneal disorders, lacrimal dysfunction, degenerative eye changes, blindness, retinal degeneration, miosis, chorioretinitis, and strabismus have been reported rarely. A case of oculogyric crisis has also been reported.[Ref]


Psychiatric side effects including two cases of intolerable aggressive behavior have been reported. One case of hypomania has also been reported.[Ref]


Dermatologic side effects including alopecia, eczema, dry skin, increased sweating, urticaria, hirsutism, seborrhea, cyst, and herpes simplex have been reported infrequently. Herpes zoster, skin discolor, skin papules, photosensitive reaction, leg ulcer, scalp seborrhea, psoriasis, desquamation, maceration, skin nodules, subcutaneous nodule, melanosis, skin necrosis, and local swelling have been reported rarely. One case of alopecia and one case of leukocytoclastic vasculitis have been reported.[Ref]


Hypersensitivity side effects including a case of hypersensitivity syndrome have been reported.[Ref]


Genitourinary side effects including hematuria, dysuria, urination frequency, cystitis, urinary retention, urinary incontinence, vaginal hemorrhage, amenorrhea, dysmenorrhea, menorrhagia, breast cancer, inability to climax, and abnormal ejaculation have been reported infrequently. Kidney pain, leukorrhea, pruritus genital, renal stone, acute renal failure, anuria, glycosuria, nephrosis, nocturia, pyuria, urination urgency, vaginal pain, breast pain, and testicle pain have been reported rarely.[Ref]


Musculoskeletal side effects including arthralgia have been reported frequently. Tendinitis, arthritis, joint stiffness, joint swelling, and positive Romberg test have been reported infrequently. Costochondritis, osteoporosis, bursitis, and contracture have been reported rarely. Myoclonus has also been reported. Postmarketing reports have included rhabdomyolysis and elevated creatine kinase.[Ref]


General side effects have included asthenia, malaise, and facial edema which have been reported frequently. Generalized edema, weight decrease, and chill have been reported infrequently. Lassitude, "strange feelings", alcohol intolerance, and hangover effect have been reported rarely.[Ref]


Endocrine side effects including hyperthyroid, hypothyroid, swollen testicle, goiter, hypoestrogenism, ovarian failure, epididymitis, and cushingoid appearance have been reported rarely. Endocrine side effects reported postmarketing have included breast enlargement.


Respiratory side effects including pneumonia have been reported frequently. Epistaxis, dyspnea, and apnea have been reported infrequently. Mucositis, aspiration pneumonia, hyperventilation, hiccup, laryngitis, nasal obstruction, snoring, bronchospasm, hypoventilation, and lung edema have been reported rarely.


Hepatic side effects including hepatomegaly have been reported infrequently. Several cases of hepatotoxicity have also been reported.[Ref]


Male rats receiving doses of gabapentin (the active ingredient contained in Fanatrex) of up to 2000 mg/kg for 2 years have developed acinar cell carcinoma of the pancreas.[Ref]

Oncologic side effects have been reported in animal studies.[Ref]


Renal side effects including two cases of marked increase in serum creatinine measurements following the introduction of gabapentin (the active ingredient contained in Fanatrex) have been reported.[Ref]


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

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.