<p><strong>Potentially life-threatening effects</strong>: Severe effects from 5-fluorouracil are related to the dosage and duration of therapy.<br />
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<strong>Cardiac effects</strong>: Occasional case reports associating 5-fluorouracil therapy with &#39;ischemic cardiac events&#39; evidence against the autoimmune phenomenon is the fact that in several cases cardiotoxicity occurred within several hours of the first dose.<br />
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<strong>Hematological effects</strong>: Potentially lethal effects caused by severe hematological toxicity may develop within the first 10 days of treatment being instituted but generally resolves within 3 weeks. At the recommended dose and schedule it is rather uncommon for hematological toxicity to be severe. Any ontribute to severe effects from 5-fluorouracil on the blood-forming cells. Thus extensive prior irradiation or the concomitant use of cytotoxic drugs tend to exacerbate the severity of the hematological side effects of 5-fluorouracil.<br />
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<strong>Neurological effects</strong>: Effects on the central nervous system have been occasionally reported and cerebral ataxia is dose-dependent with an incidence of between 3.1 and 7%. Acute cerebellar syndromes and myelopathy have been described following intrathecal 5-fluorouracil. Neurological syndromes may occur rarely after carotid artery perfusion in head and neck cancer. Other effects Allergic reaction (including difficulty in breathing, closing of the throat, swelling of the lips, tongue, or face, or hives), decreased bone marrow function and blood problems (extreme fatigue, easy bruising or bleeding, black, bloody or tarry stools, or fever, chills, or signs of infection), hand-foot syndrome (tingling, pain, redness, swelling or tenderness of the hands and feet), severe vomiting, diarrhoea, frequent bowel movements or watery stools, or sores in the mouth or throat, or stomach pain or heartburn or black, bloody or tarry stools. Other less serious side effects may include mild to moderate nausea, vomiting or loss of appetite, balance problems, confusion, rash and itching, or temporary hair loss. Conjunctivitis, both acute and chronic can proceed to tear duct stenosis and ectropion following prolonged administration. Very chronic administration, extending beyond 3 months, of low dosage has been associated with low systemic toxicity but includes the possibility of painful and tender hands and feet associated with erythema of the extremities.</p>