5-Fluorouracil Ebewe Drug Interactions

All therapeutic measures aggravating the patient's physical status or impairing myeloid functions (e.g. other cytostatics) may increase the toxicity of fluorouracil.
Fluorouracil can potentiate the cutaneous toxicity of radiotherapies.
Calcium folinate enhances the effect of fluorouracil. Severe, partially lethal diarrhoea may occur as clinical sequel of this interaction. Accumulation of such deaths has been reported especially in association with an administration scheme of an i.v. bolus of 600 mg/m² body surface area fluorouracil once weekly in combination with calcium folinate.
The enzyme dihydropyrimidine dehydrogenase (DPD) plays an important role for the degradation of 5-FU. Nucleoside analogues, such as brivudine and sorivudine, may lead to a drastic increase in the plasma concentrations of 5-FU or other fluoropyrimidines and thus to an accompanying increase in toxicity.
For this reason, an interval of at least 4 weeks should be kept between intake of 5-FU and brivudine, sorivudine and analogues. If necessary, determination of the DPD enzyme activity is indicated prior to therapy with 5-fluoropyrimidines.
In case of concomitant administration of phenytoin and fluorouracil, an increase in the plasma level of phenytoin has been reported, which led to symptoms of phenytoin intoxication.
Cimetidine, metronidazole and interferons may increase the plasma level of fluorouracil. This can potentiate the toxic effects of fluorouracil.
In female patients receiving a diuretic of the thiazide type additionally to cyclophosphamide, methotrexate and fluorouracil, the granulocyte count was more reduced than after equal cytostatic cycles without thiazide.
Isolated cases of a decline in the Quick's value were observed in patients treated with warfarin and additionally receiving fluorouracil alone or in combination with levamisole.
During treatment with fluorouracil and levamisole, hepatotoxic effects (increase in alkaline phosphatase, transaminases or bilirubin) are frequently observed.
Patients with mammary carcinoma receiving combination treatment with cyclophosphamide, methotrexate, fluorouracil and tamoxifen showed an aggravated risk of the occurrence of thromboembolic events.
In case of coincident administration of vinorelbine and fluorouracil/folinic acid, severe mucositis resulting in death may occur.
The assay techniques for bilirubin and 5-hydroxyindole acetic acid in urine may yield elevated or false positive values.
General notes: Cytostatics can reduce the antibody formation after influenza vaccination. Cytostatics may elevate the risk of an infection after live vaccine.