Fluorouracil
Unchecked
Fluorouracil (5-FU)
Efudex (topical), Carac (topical), Fluoroplex (topical); generic IV
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Summary
Common uses
Actinic keratosis (topical)0, Superficial basal cell carcinoma (topical)0, Colorectal and other GI malignancies (IV systemic, in regimens)0, Breast cancer (IV, in regimens)0
Pharmacy
Starting dose
Topical: 0.5-5% cream/solution to lesions BID × 2-4 weeks; systemic IV: regimen-specific in cancer chemotherapy
Preparations
0.5% (Carac), 1% (Fluoroplex), 5% (Efudex) topical creams/solutions; 50 mg/mL IV
US FDA Max
Topical: nightly; systemic: regimen-specific
Pharmacology
Routes
Topical, IV
Onset
Topical: inflammation, erythema, crusting at 2 weeks; complete response weeks to months after course
Duration
N/A
Half-life
~10-20 minutes systemically (rapid hepatic and erythrocyte dihydropyrimidine dehydrogenase clearance)[2]
Bioavailability
Topical: minimal systemic absorption (oral systemic 5-FU not used due to poor and variable absorption)[2]
Pregnancy
Topical: avoid; systemic: contraindicated in pregnancy.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Fluorouracil is a fluorinated pyrimidine analog incorporated into RNA and converted to fluorodeoxyuridine monophosphate (FdUMP), which covalently inhibits thymidylate synthase and blocks de novo dTMP synthesis; the resulting "thymineless death" is most potent against rapidly dividing cells.0 Severe systemic toxicity (myelosuppression, mucositis, diarrhea, hand-foot syndrome, neurotoxicity in 5-10%) is amplified in patients with dihydropyrimidine dehydrogenase (DPYD) deficiency; CPIC-supported pre-treatment DPYD genotyping is standard in many oncology centers[1]. Topical actions reproduce the same antimetabolite effect locally with minimal systemic absorption.
References
[edit | edit source]- ↑ CPIC Guideline for DPYD and Fluoropyrimidines, 2017 (update 2024). https://cpicpgx.org/guidelines/guideline-for-fluoropyrimidines-and-dpyd/
- ↑ 2.0 2.1 FDA Prescribing Information, Efudex (fluorouracil) topical, Valeant/Bausch, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/016831s050lbl.pdf