Fluorouracil, Capecitabine, Tegafur (Adverse effects)

Fluoropyrimidines are a family of chemotherapeutic drugs widely used in cancer treatment. Between 10 and 40% of individuals treated with these drugs develop adverse effects and this has been associated with the presence of certain variants in the DPYD gene, directly involved in their metabolism.

The family of antineoplastic drugs known as fluoropyrimidines (fluorouracil, capecitabine, tegafur, among others) is composed of chemotherapeutic agents that are widely used in the treatment of different types of cancers. Fluoropyrimidines belong to a family of antineoplastic drugs called antimetabolites. The most serious side effects that fluoropyrimidines can cause are neurotoxicity and suppression of the bone marrow, among others.

Fluorouracil, which is often called 5FU, is used to treat different types of cancer such as breast, bowel, skin, stomach, esophagus (throat) and pancreas. The most common side effects of fluorouracil are: infections, bleeding, anemia, nausea, diarrhea, loss of appetite, pain in the mouth, taste disturbances, tiredness, tingling of hands and feet, hair loss, arrhythmia. Other less common side effects of fluorouracil are: pain in the eyes, sensitivity in the skin that causes pain, risk of clots (symptoms are pain, redness and swelling in the extremities, difficulty breathing and chest pain), neurotoxicity, bone marrow suppression.

Capecitabine is used as chemotherapy to treat metastatic cancer of the colon or rectum and metastatic breast cancer. It is a prodrug of fluororuracil, that is, in the organism it is converted to fluororuracil. The most common side effects of treatment with capecitabine, with an incidence greater than 30%, are: anemia, fatigue, diarrhea, foot and hand syndrome (palmar-plantar erythrodysesthesia or PPE, the symptoms are rash, swelling, redness, pain and/peeling of the skin on the palms of the hands and the soles of the feet. It is usually mild and begins 2 weeks after the start of treatment.It may require a reduction in the dose of the drug), nausea and vomiting, dermatitis, increase in hepatic enzymes, bilirubin increase. Other less frequent side effects (incidence between 10-29%) are: low appetite, abdominal pain, infections, hemorrhages, constipation, fever, dyspnea, chest pain, insomnia, blood clots, excessive drowsiness, confusion, seizures, loss of equilibrium, changes in the nails, darkening of the skin, neurotoxicity, bone marrow suppression.

Tegafur is used to treat colon and rectal cancer, as well as stomach, breast and pancreatic cancer. It is a prodrug of fluororuracil, that is, in the organism it is converted to fluororuracil. The most common side effects of tegafur are: risk of infection, hemorrhage, anemia, nausea, diarrhea, abdominal pain, loss of appetite, pain in the mouth, fatigue, alterations in the liver. Other less common side effects are: hair loss, skin changes, taste changes, watery eyes, risk of blood clots, chest pain, arrhythmias, neurotoxicity.


  • Fluorouracil: Efudex®, Adrucil®, CaracTM®, Fluoroplex®
  • Capecitabine: Xeloda®
  • Tegafur: Utefos®, UFT®

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