Action And Clinical Pharmacology: There is evidence that the metabolism of fluorouracil in the anabolic pathway blocks the methylation reaction of deoxyuridylic acid to thymidylic acid. In this fashion fluorouracil interferes with the synthesis of deoxyribonucleic acid (DNA) and, to a lesser extent, inhibits the formation of ribonucleic acid (RNA). Since DNA and RNA are essential for cell division and growth, the effect of fluorouracil may be to create a thymine deficiency which provokes unbalanced growth and death of the cell. The effects of DNA and RNA deprivation are most marked on those cells which grow more rapidly and which take up fluorouracil at a more rapid pace. The catabolic metabolism of fluorouracil results in degradative products (e.g., CO2, urea, alpha-fluoro-beta-alanine) which are inactive.
Studies in man with topical application of C4labelled ‘Efudex’ demonstrate insignificant absorption as measured by C4content of plasma, urine and respiratory CO2.
Indications And Clinical Uses: Recommended for the topical treatment of premalignant keratoses and superficial basal cell carcinoma.
Contra-Indications: In patients with known hypersensitivity to any of its components.
Manufacturers’ Warnings In Clinical States: If an occlusive dressing is used, there may be an increase in the incidence of inflammatory reactions in the adjacent normal skin.
Prolonged exposure to ultraviolet light should be avoided while under treatment with fluorouracil because the intensity of the reaction may be increased.
Pregnancy: Since fluorouracil is known to have teratogenic properties, the potential value of its use in women of child-bearing potential should be weighed against the risks involved.
Appropriate therapy for pre-existing concomitant inflammatory dermatoses should be instituted before using the drug.
Precautions: The cream is preferably applied with a nonmetal applicator or suitable glove; if it is applied with the fingertips, the hands should be washed immediately afterward. Fluorouracil should be applied with care near the eyes, nose and mouth. To rule out the presence of a frank neoplasm, a biopsy should be made of those lesions failing to respond to treatment or recurring after treatment.
Adverse Reactions: The most frequently encountered local reactions are pain, pruritus, hyperpigmentation and burning at the site of application. Other local reactions include dermatitis, scarring, soreness and tenderness. Insomnia, stomatitis, suppuration, scaling, swelling, irritability, medicinal taste, photosensitivity and lacrimation have also been reported.
Laboratory abnormalities reported include leukocytosis, thrombocytopenia, toxic granulation and eosinophilia.
Symptoms And Treatment Of Overdose: Symptoms: Since fluorouracil is applied topically, it is highly unlikely that an overdosage would occur. In the event that this preparation is accidentaly ingested, signs of toxicity may include diarrhea, stomatitis, thrombocytopenia.
Treatment: These symptoms may be ameliorated by leucovorin.
Dosage And Administration: The cream should be applied twice daily with a nonmetal applicator or suitable glove in an amount of the cream sufficient to cover the lesion. When applied to a lesion, a response occurs with the following sequence: erythema, usually followed by vesiculation, erosion, ulceration, necrosis and epithelization. The lower frequency and intensity of activity in adjacent normal skin indicate a selective cytotoxic property. Medication should be continued until the inflammatory reaction reaches the erosion, necrosis, and ulceration stage, at which time use of the drug should be terminated. The usual duration of therapy is from 2 to 4 weeks. Complete healing of the lesion may not be evident for 1 to 2 months following cessation of fluorouracil therapy.
While the patient is undergoing topical fluorouracil therapy, consideration can be given to curettage, wound excision and removal of pathological tissue.
Availability And Storage: Each g of cream contains: fluorouracil 5% (50 mg/g) in a vanishing cream base. Nonmedicinal ingredients: methylparaben, polysorbate 60, propylene glycol, propylparaben, stearyl alcohol and white petrolatum. Sulfite-free. Tubes of 25 g. Store at 15 to 30°C. For external use only.
EFUDEX® ICN Fluorouracil Topical Antineoplastic