Fluorouracil: Nursing Drug Guide, Myelosuppression & Hold Rules

Fluorouracil (5-FU) is supplied as an intravenous injection concentrate. Gland Pharma labeling lists 50 mg/mL vials as 500 mg/10 mL and 1 g/20 mL. Verify strength, regimen (bolus vs continuous infusion), and pump programming on the MAR—do not inject an entire vial unless the full vial dose is explicitly ordered.

Regimens often pair 5-FU with leucovorin (folinic acid) in colorectal protocols; confirm both agents, sequence, and infusion duration before IV insertion and pump setup.

Labeling indicates fluorouracil for adenocarcinoma of the colon and rectum, adenocarcinoma of the breast, gastric adenocarcinoma, and pancreatic adenocarcinoma. Nurses in oncology infusion suites administer regimen-specific IV schedules—not interchangeable single daily doses.

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Fluorouracil is an antimetabolite that interferes with DNA and RNA synthesis in rapidly dividing cells. Nursing focus is not mechanism memorization but cytotoxic handling, myelosuppression timing, and DPD deficiency: patients who cannot adequately degrade fluoropyrimidines may develop severe, life-threatening toxicity. Labeling recommends considering DPYD testing before initiation when clinically appropriate.

All doses are regimen-specific and require BSA-based calculation, pharmacy verification, and institutional chemotherapy protocols. Examples below are from Gland Pharma fluorouracil injection labeling—always verify the active order.

Renal/hepatic adjustment: Not specified in the reviewed prescribing information—follow institutional oncology protocols and prescriber orders.

Missed dose: Not specified in the reviewed prescribing information. Contact oncology pharmacy for cycle timing guidance.

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Pretreatment checks

• CBC with differential before each treatment—labeling requires CBC prior to each cycle
• Review prior-cycle nadir counts and whether Grade 4 myelosuppression has resolved
• Medication reconciliation for warfarin and other interacting drugs
• DPYD / DPD deficiency history or prior severe fluoropyrimidine toxicity—consider testing per labeling
• Pregnancy status; effective contraception required per labeling (see high-risk groups)
• Confirm correct BSA, regimen, bolus vs infusion bag, and pump duration

Contraindications

Labeling states None—clinical use still requires assessment of severe toxicity, hypersensitivity, and regimen-specific hold criteria.

Important interactions

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IV fluorouracil is a hazardous cytotoxic drug—use appropriate PPE, spill kits, and waste disposal per facility and OSHA hazardous drug guidance cited in References. Follow medication administration rights and oncology double-checks.

• Do not inject the entire vial unless the complete vial dose is ordered—verify mg vs mL (50 mg/mL)
• Administer bolus and continuous infusion per protocol; program pump for ordered duration (e.g., 46-hour CI in FOLFOX-style regimens)
• No other medications in the same IV line during fluorouracil infusion per labeling
• Document start/stop times, actual volume infused, and any extravasation signs
• Separate leucovorin and 5-FU sequence per prescriber/pharmacy plan when both are ordered

• Tumor response is assessed by the oncology team over cycles—not at the bedside during a single infusion
• Counts remain adequate to proceed with the next cycle per prescriber thresholds
• Toxicity remains manageable without Grade 4 myelosuppression or hold-level diarrhea, mucositis, or hand-foot syndrome
• Stable INR when warfarin is concurrent and monitoring is in place

• Fever ≥38°C (100.4°F) or rigors with neutropenia—febrile neutropenia pathway
• ANC at Grade 4 or prescriber-defined hold threshold—do not administer next cycle until cleared
• Grade 3–4 diarrhea, Grade 3–4 mucositis, or Grade 2–3 hand-foot syndrome per labeling hold criteria
• Chest pain, dyspnea, or arrhythmia—possible cardiotoxicity; obtain ECG per protocol
• Acute confusion or altered mental status—consider hyperammonemic encephalopathy; hold drug and escalate urgently
• Signs of anaphylaxis during infusion—stop infusion and treat per protocol
• Active bleeding or supratherapeutic INR on warfarin

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Fluorouracil overdose (including excessive infusion rates or dosing errors) requires immediate oncology and toxicology involvement.

Antidote

Labeling states: administer uridine triacetate within 96 hours following the end of the fluorouracil infusion for management of fluorouracil overdose. Contact local poison control or toxicology services per facility protocol.

Supportive care

Discontinue fluorouracil, provide supportive care for cytopenias, diarrhea, mucositis, and organ-specific toxicity per institutional protocols. Dialysis removal: Not specified in the reviewed prescribing information.

• Fluorouracil vs floxuridine—both fluoropyrimidines; verify drug name and concentration on vial and MAR
• 5-FU vs leucovorin—often given in sequence; label bags and lines clearly
• mg vs mL at 50 mg/mL—double-check pump programming for continuous infusion total dose over 46 hours
• Entire-vial injection—labeling warns not to inject the entire vial unless the full vial dose is intended
• Look-alike vial strengths—500 mg/10 mL vs 1 g/20 mL; use barcode scanning when available

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Monitor

• CBC with differential before each treatment and through days 9–14 nadir window
• Signs of infection, bleeding, or fatigue during cytopenic period
• Stool frequency, oral mucosa, palms/soles for hand-foot syndrome
• INR when warfarin is concurrent
• Cardiac and neurologic symptoms per prescriber plan

Document

• Pre-treatment CBC result and clearance to treat
• Bolus dose, CI rate, pump settings, and actual infusion times
• Patient teaching on nadir timing, fever instructions, and when to call oncology
• Any held or modified doses with prescriber/pharmacy communication

• Your blood counts are usually lowest about 9–14 days after treatment—this is when infection risk is highest
• Call oncology immediately for fever, chills, uncontrolled diarrhea, mouth sores preventing fluids, confusion, chest pain, or bleeding
• Use contraception during treatment and for 3 months after the last dose; discuss pregnancy and breastfeeding with your team
• Do not take warfarin dose changes without INR monitoring when on 5-FU
• If you have a home infusion pump, know disconnect time and emergency contact—do not add other drugs to the line

Hold parameters may vary by institutional protocol and regimen. Follow prescriber orders and oncology pharmacy guidance.

Practice NCLEX-style clinical judgment practice for fluorouracil myelosuppression safety using a tabbed outpatient oncology case (MAR, labs, vitals, nursing notes), then priority action, cue recognition (SATA), nadir trend interpretation, matrix urgency, documentation cloze, and antidote selection—recognise cues → analyse → prioritise → act → evaluate outcomes.

This medication guide is written and reviewed using NurseOnShift editorial and clinical review standards.

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Educational use only. This content does not replace clinical judgment, prescriber orders, pharmacist guidance, product labeling, or institutional protocols.