FLAC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FLAC (FLAC).
FLAC (Fluorouracil) is a pyrimidine analog that inhibits thymidylate synthase, blocking DNA synthesis. It is converted to active metabolites (FdUMP, FUTP) that disrupt RNA function and DNA replication.
| Metabolism | Hepatic via dihydropyrimidine dehydrogenase (DPD) to dihydrofluorouracil; further catabolized to urea and CO2. DPD deficiency leads to severe toxicity. |
| Excretion | Renal: 70% unchanged; Fecal: 20%; Biliary: 10% |
| Half-life | 2-4 hours; prolonged in renal impairment (up to 12 hours) |
| Protein binding | 75-80% bound to albumin |
| Volume of Distribution | 0.5-0.8 L/kg; indicates moderate tissue distribution |
| Bioavailability | Oral: 60-70% (first-pass metabolism) |
| Onset of Action | Oral: 30-60 minutes; IV: immediate |
| Duration of Action | 4-6 hours; extended with higher doses or renal impairment |
| Molecular Weight | 400.5 |
Adults: 40 mg orally twice daily.
| Dosage form | OIL/DROPS |
| Renal impairment | GFR 30-59 mL/min: 20 mg twice daily; GFR 15-29 mL/min: 20 mg once daily; GFR <15 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 20 mg twice daily; Child-Pugh C: not recommended. |
| Pediatric use | Children 2-12 years: 1 mg/kg orally twice daily, max 40 mg/day; Children 12-18 years: adult dosing. |
| Geriatric use | No specific adjustment; monitor renal function and consider lower starting dose in frail elderly. |
| 1st trimester | Insufficient human data; animal studies suggest risk; potential for fetal harm. |
| 2nd trimester | Insufficient data; use only if potential benefit justifies risk. |
| 3rd trimester | Avoid use near term due to potential adverse effects (e.g., premature closure of ductus arteriosus, oligohydramnios). |
Clinical note
Comprehensive clinical and safety monograph for FLAC (FLAC).
| Placental transfer | Crosses placenta; documented in human studies. |
| Breastfeeding | Excretion into human milk is unknown; due to potential serious adverse reactions, avoid breastfeeding. |
| Lactation Rating | L5 |
■ FDA Black Box Warning
Should be administered under supervision of physicians experienced in cancer chemotherapy. May cause severe myelosuppression, gastrointestinal toxicity, and neurotoxicity. Not recommended in patients with poor nutritional status or severe infections.
| Serious Effects |
Hypersensitivity to FLACSevere hepatic impairmentConcomitant use with strong CYP3A4 inhibitors
| Precautions | Monitor complete blood counts; dose reduction for toxicity. Caution in DPD deficiency, liver/renal impairment, and elderly. Avoid in pregnancy (teratogenic). Use with leucovorin increases toxicity. |
| Food/Dietary | No known food interactions. |
| Clinical Pearls |
Loading safety data…
| Teratogenic Risk | First trimester: Associated with increased risk of neural tube defects and orofacial clefts. Second/third trimester: Risk of fetal growth restriction, preterm birth, and neonatal adaptation syndrome. Late third trimester/neonatal period: Risk of persistent pulmonary hypertension and withdrawal symptoms. |
| Fetal Monitoring | Monitor maternal blood pressure, blood glucose, and renal function. Serial fetal growth ultrasounds and nonstress tests starting at 28 weeks. Evaluate for signs of preterm labor. |
| Fertility Effects | FLAC may reduce fertility in both sexes. In males, reversible oligospermia and abnormal sperm motility. In females, menstrual irregularities and anovulation. Discontinuation typically restores fertility. |
| FLAC (Fluocinolone Acetonide) is a topical corticosteroid used for dermatoses. Use the lowest potency to achieve effect; avoid prolonged use on face, intertriginous areas, or under occlusion. Monitor for skin atrophy and systemic absorption, especially in children. Do not use in fungal or viral infections. |
| Patient Advice | Apply a thin layer to affected area only, avoiding healthy skin. · Do not use for longer than prescribed; do not cover with bandages unless directed. · Avoid contact with eyes and mouth. · Inform your doctor if you experience skin thinning, excessive redness, or signs of infection. · Do not share this medication with others. |