Drug Interactions between allopurinol and fluorouracil

Products containing folic acid may increase the effects of fluorouracil. You may be more likely to develop serious side effects such as anemia, bleeding problems, infections, and nerve damage when these medications are used together. Contact your doctor if you experience severe nausea and vomiting, diarrhea, paleness of skin, fatigue, dizziness, fainting, unusual bleeding or bruising, blood in the stools, fever, chills, body aches, flu-like symptoms, skin reactions, mouth ulcers or sores, and/or numbness, burning or tingling in your hands and feet. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

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ADJUST DOSING INTERVAL: The tolerability of allopurinol may be improved by giving it after a meal. Additionally, when the dose is greater than 300 mg, dividing the total daily dose into smaller doses administered more often may be appropriate to help minimize gastrointestinal irritation.

MONITOR: Concomitant use of allopurinol with central nervous system (CNS) depressants, including alcohol, may potentiate adverse effects such as somnolence and sedation.

MANAGEMENT: To improve tolerability, some manufacturers suggest administering allopurinol after a meal. Additionally, if the daily dose is greater than 300 mg, administering allopurinol in divided doses may help reduce gastrointestinal intolerance. Patients should also be counseled to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them.