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Fluorouracil Side Effects

For the Consumer

Applies to fluorouracil: injectable, solution

In addition to its needed effects, some unwanted effects may be caused by fluorouracil. In the event that any of these side effects do occur, they may require medical attention.

Also, because of the way these medicines act on the body, there is a chance that they might cause other unwanted effects that may not occur until months or years after the medicine is used. These delayed effects may include certain types of cancer, such as leukemia. Discuss these possible effects with your doctor.

Major Side Effects

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

More common:
  • Diarrhea
  • heartburn
  • sores in mouth and on lips
Less common:
  • Black, tarry stools
  • cough or hoarseness, accompanied by fever or chills
  • fever or chills
  • lower back or side pain, accompanied by fever or chills
  • nausea and vomiting (severe)
  • painful or difficult urination, accompanied by fever or chills
  • stomach cramps
  • Blood in urine or stools
  • pinpoint red spots on skin
  • unusual bleeding or bruising

Severity: Moderate

If any of the following side effects occur while taking fluorouracil, check with your doctor or nurse as soon as possible:

  • Chest pain
  • cough
  • shortness of breath
  • tingling of hands and feet, followed by pain, redness, and swelling
  • trouble with balance

Minor Side Effects

Some of the side effects that can occur with fluorouracil 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:
  • Loss of appetite
  • nausea and vomiting
  • skin rash and itching
  • weakness
Less common:
  • Dry or cracked skin

This medicine often causes a temporary loss of hair. After treatment with fluorouracil has ended, normal hair growth should return.

Side Effects: Post Treatment

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

  • Black, tarry stools
  • blood in urine or stools
  • cough or hoarseness, accompanied by fever or chills
  • fever or chills
  • lower back or side pain, accompanied by fever or chills
  • painful or difficult urination, accompanied by fever or chills
  • pinpoint red spots on skin
  • unusual bleeding or bruising

For Healthcare Professionals

Applies to fluorouracil: compounding powder, intravenous solution


Very common (10% or more): Ischemic ECG abnormalities
Common (1% to 10%): Angina pectoris-like chest pain
Uncommon (0.1% to 1%): Arrhythmia, myocardial infarction, myocardial ischemia myocarditis, heart insufficiency, dilative cardiomyopathy, cardiac shock, hypotension
Rare (0.01% to 0.1%): Cerebral, intestinal and peripheral ischemia, Raynaud's syndrome, thromboembolism
Very rare (less than 0.01%): Cardiac arrest, sudden cardiac death
Frequency not reported: Tachycardia[Ref]


Very common (10% or more): Palmar-plantar erythrodysesthesia syndrome (hand-foot syndrome), alopecia
Uncommon (0.1% to 1%): Dermatitis, skin alterations (e.g., dry skin, fissure erosion, erythema, pruritic maculopapular rash), exanthema, urticaria, photosensitivity, hyperpigmentation, streaky hyperpigmentation or depigmentation near the veins, changes in nails (e.g., diffuse superficial blue pigmentation, hyperpigmentation, nail dystrophy, pain and thickening of the nail bed, paronychia), onycholysis[Ref]


Rare (less than 0.1%): Total thyroxin (T4) increased, total triiodothyronine (T3) increased[Ref]


Very common (10% or more): Mucositis (stomatitis, esophagitis, pharyngitis, proctitis), anorexia, watery diarrhea, nausea, vomiting
Uncommon (0.1% to 1%): Dehydration, GI ulceration, GI bleeding, GI sloughing
Frequency not reported: Dysphagia[Ref]


Uncommon (0.1% to 1%): Spermatogenesis, ovulation disorder
Frequency not reported: Urinary tract infection[Ref]


Very common (10% or more): Myelosuppression, neutropenia, thrombocytopenia, leucopenia, agranulocytosis, anemia, pancytopenia
Rare (less than 0.1%): Thrombophlebitis/vein tracking[Ref]


Uncommon (0.1% to 1%): Liver cell damage
Very rare (less than 0.01%): Liver necrosis, biliary sclerosis, cholecystitis[Ref]


Rare (less than 0.1%): Generalized allergic reactions, anaphylaxis, anaphylactic shock[Ref]


Very common (10% or more): Immunosuppression with an increased risk of infection
Frequency not reported: Sepsis, septic shock, neutropenic sepsis, super infection, cellulitis[Ref]

Nervous system

Uncommon (0.1% to 1%): Headache, dizziness, Parkinson's disease like symptoms, pyramidal signs
Very rare (less than 0.01%): Symptoms of leukoencephalopathy (including ataxia, acute cerebellar syndrome, dysarthria, confusion, disorientation, myasthenia, aphasia, convulsion, or coma in patients receiving high doses and in patients with dihydropyrimidine dehydrogenase deficiency)
Frequency not reported: Peripheral neuropathy, acute cerebellar syndrome[Ref]


Uncommon (0.1% to 1%): Nystagmus, excessive lacrimation, blurred vision, eye movement disturbance, optic neuritis, diplopia, decrease in visual acuity, photophobia, conjunctivitis, blepharitis, ectropion, dacryostenosis[Ref]


Very rare (less than 0.01%): Kidney failure[Ref]


Uncommon (0.1% to 1%): Euphoria, somnolence
Rare (0.01% to 0.1%): Confusion
Very rare (less than 0.01%): Disorientation[Ref]


Very common (10% or more): Bronchospasm, epistaxis
Frequency not reported: Breathlessness, pneumonia, pharyngitis[Ref]


1. "Product Information. Fluorouracil (fluorouracil)." BluePoint Laboratories, Norwich, NY.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. Cerner Multum, Inc. "Australian Product Information." O 0

Not all side effects for fluorouracil 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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