VetSheet

フルオロウラシル

Fluorouracil

5-fluorouracil

抗悪性腫瘍薬 - ピリミジン拮抗薬IVIntralesionalTopical犬猫馬

別名: Adrucil · Efudix · 5-FU · 5-fluorouracil · fluorouracilo · fluorouracilum · NSC-19893 · Ro-2-9757 · WR-69596

VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス

150 mg/m2 IV weekly, or 5-10 mg/kg IV weeklyIV· weekly

これは体表面積（mg/m²）に基づく用量です。投与前に体重を体表面積へ換算してください。

用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。

動物種別用量

🌎 NA — North America🌍 EU — Europe

犬

適応用量経路頻度期間地域
Canine mammary carcinoma (in combination with doxorubicin and cyclophosphamide-FAC protocol), dermal squamous cell carcinoma and GI tract tumors150 mg/m2 IV weekly, or 5-10 mg/kg IV weeklyIVweekly—🌎 NA
Systemic carcinomas150 mg/m2IVonce weekly OR once every 3 weeks when combined with carboplatin6 weeks (if used weekly)🌍 EU
Basal cell and squamous cell carcinomaApply to affected areatopicalq24hAs directed by oncologist🌍 EU
  • Systemic carcinomas: Reduce dose by half in patients with liver, renal, or bone marrow impairment.
  • Basal cell and squamous cell carcinoma: Wear gloves when applying. Prevent the dog from licking the area.

猫

適応用量経路頻度期間地域
ALLCONTRAINDICATEDALL——🌎 NA
All indicationsDO NOT USEPO/IM/IV/SC/topicalnullnull🌍 EU
  • ALL: Do NOT use in any form on cats
  • All indications: Strictly contraindicated. Causes potentially fatal neurotoxicity.

馬

適応用量経路頻度期間地域
Intratumoral injection with epinephrine into certain skin neoplasms (squamous cell carcinoma, melanoma, sarcoid)0.3 mL of 1:1000 epinephrine is added to each mL of 5-FU solution up to a maximum of 3 mL of epinephrine per total volume of 5-FU injected.Intratumoral——🌎 NA
  • Intratumoral injection with epinephrine into certain skin neoplasms (squamous cell carcinoma, melanoma, sarcoid): Epinephrine may result in white hair growth and can cause transient excitation, tachycardia, and shaking if absorbed systemically in sufficient quantities.

用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。

診察中ですか？VetSheet の AI が薬剤・用量・投与期間を構造化された診察記録に直接記入します。VetSheet の仕組みを見る

概要

フルオロウラシル (5-FU) は、獣医学において特定の種類の癌の治療に使用されるピリミジンアナログの抗悪性腫瘍薬です。

  • ​犬​: 乳癌（通常、ドキソルビシンおよびシクロホスファミドと併用するFACプロトコルの一部として）、皮膚扁平上皮癌、および消化管腫瘍に対して全身的に使用されます。
  • ​馬​: 扁平上皮癌、悪性黒色腫、馬サルコイドなどの皮膚腫瘍を治療するために、局所または病変内注射（多くの場合エピネフリンと併用）として使用されます。

​重大な動物種間の違い​: 5-FUは​猫には絶対禁忌​です。猫にはこの薬物を安全に処理するために必要な代謝経路が欠如しており、ごく微量（人間用の外用クリームの誤飲など）であっても、重度で急速に進行し、多くの場合致命的な神経毒性を引き起こします。

作用機序

Fluorouracil is a prodrug that acts as a cell-cycle phase-specific (S-phase) antimetabolite. It enters the cell and is converted into two primary active metabolites:

  • ​FUMP (fluorouridine monophosphate)​ → Inhibits the enzyme thymidylate synthase, which blocks the synthesis of deoxythymidine triphosphate (dTTP). This severely disrupts DNA synthesis and repair.
  • ​FUTP (fluorouridine triphosphate)​ → Falsely incorporates into RNA, disrupting RNA processing, function, and subsequent protein synthesis.

By halting both DNA and RNA functions, the drug induces apoptosis in rapidly dividing cancer cells.

安全性・警告

禁忌

  • CATS (Do NOT use in any form, including topical)
  • Patients with known hypersensitivity to the drug
  • Patients in poor nutritional states
  • Patients with depressed or reduced bone marrow function
  • Patients with concurrent serious infections
  • Pregnancy (Known teratogen - FDA Category D)
  • Cats (strictly contraindicated due to fatal neurotoxicity)
  • Patients with severe bone marrow suppression
  • Patients with severe hepatic or renal impairment (unless dose is adjusted)
  • Pregnancy and lactation

有害事象

  • Dose-dependent myelosuppression (leukopenia, thrombocytopenia)
  • Gastrointestinal toxicity (nausea, vomiting, hemorrhagic diarrhea, GI ulceration/sloughing, stomatitis)
  • Neurotoxicity (ataxia, disorientation, seizures)
  • Fatal neurotoxicity in cats (even with topical exposure)
  • Anorexia
  • Diarrhoea
  • Leucopenia (nadir between 7 and 14 days)
  • Anaemia
  • Alopecia
  • Hyperpigmentation
  • Dermatitis
  • Cerebellar ataxia

注意事項

Fluorouracil has a very narrow therapeutic index and should only be administered by clinicians experienced with cancer chemotherapeutic agents.

Feline Toxicity: Cats develop severe, potentially fatal neurotoxicity. It is contraindicated in cats in any form.

Reproductive Safety: 5-FU is a known teratogen. Pregnant women and pregnant veterinary staff should avoid handling this medication or the bodily fluids/waste of treated animals. If a nursing dam requires treatment, milk replacer should be used as the drug inhibits DNA/RNA synthesis.

医薬品相互作用

Leucovorin

May increase the gastrointestinal toxic effects of 5-FU

CimetidineMajor

Inhibits the metabolism of 5-FU, potentially increasing toxicity

CarboplatinMajor

Synergism in human oncology, but combination may be more toxic in small animals

MethotrexateMajor

Synergistic if administered before 5-FU; antagonistic if administered afterwards

VincristineMajor

Increases the cytotoxicity of 5-FU

監視

  • CBCs (nadirs usually occur between days 9-14 with recovery by day 30)
  • Gastrointestinal adverse effects (vomiting, diarrhea, anorexia)
  • Central nervous system adverse effects (ataxia, seizures)
  • Liver enzymes (alkaline phosphatase, serum transaminase), serum bilirubin, and lactic dehydrogenase (may increase)
  • Tumor response/Efficacy
  • Complete Blood Count (CBC) to monitor for leucopenia and thrombocytopenia (nadir 7-14 days)
  • Renal function parameters
  • Hepatic function parameters
  • Gastrointestinal signs (vomiting, diarrhea, stomatitis)
  • Neurological signs

薬物動態

半減期

猫Prolonged (contributes to severe toxicity)犬Short (minutes to hours depending on administration rate)

吸収

Administered systemically via the IV route.

分布

Primarily distributed into tumor cells, intestinal mucosa, liver, and bone marrow.

代謝

Converted via intracellular mechanisms to active metabolites (FUMP and FUTP); the majority of the drug is metabolized by the liver.

消失

A small amount (about 15% of dose) is excreted unchanged into the urine.

過剰投与

Overdoses are extremely serious and potentially fatal.

  • Dogs: The lowest reported toxic dose is 8.6 mg/kg (mild GI irritation/vomiting). Seizures and death have been reported at doses as low as 10.3 mg/kg, with survival rates potentially as low as 25%.
  • Cats: Very small ingestions (such as licking human topical creams) can cause death.

Clinical Signs: Onset is rapid (30 minutes to 6 hours). Signs include acute nausea, vomiting, hemorrhagic diarrhea, abdominal pain, GI sloughing, ataxia, severe nonresponsive seizures, severe dose-dependent myelosuppression affecting all cell lines, metabolic acidosis, and multi-organ failure.

Treatment:

  • Aggressive GI decontamination and protection if ingestion was very recent (though rapid onset may render this ineffective).
  • Intensive supportive care: antiemetics, fluid support, pain control, and temperature regulation.
  • Seizure control: Diazepam is often unrewarding; barbiturates or general anesthesia are frequently required.
  • Broad-spectrum antibiotics to prevent secondary infections.
  • Filgrastim (Neupogen®) can be considered to stimulate bone marrow stem cell proliferation in dogs.
  • Intensive hematologic monitoring (CBCs every 3-4 days) for at least 3-4 weeks.

製品

製剤

  • Injection solution
  • Topical solution
  • Injectable solution: 250 mg/vial, 500 mg/vial, 2500 mg/vial
  • Topical cream: 5%

ヒト用医薬品

  • Fluorouracil Injection: 50 mg/mL in 10 mL, 20 mL, 50 mL, & 100 mL vials and 10 mL amps (Adrucil®; generic)
  • Topical creams and solutions: 0.5% to 5% (used for actinic keratoses and superficial basal cell carcinomas)
  • Efudix 5% cream
  • Fluorouracil injectable solutions (various generics)

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

Human-approved drug used under the cascade.

United Kingdom✓ 承認済み処方箋医薬品VMD

POM. Used under the prescribing cascade.

規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

保管・安定性

Store injection between 15-30°C; avoid freezing and exposure to light. Slight color changes in the solution can be ignored. If a precipitate forms, the solution can be heated to 60°C and shaken vigorously to redissolve the drug. Cool to body temperature before administering. If unsuccessful in redissolving the drug, it should not be used.

飼主向け情報

​猫の飼い主への重大な警告​: 5-FUを含む人間用の外用クリーム（皮膚病変に使用）は、猫にとって​非常に毒性が高く、多くの場合致命的​です。ほんの少し舐めたり、薬を塗った場所を歩いて毛づくろいをしただけでも死に至る可能性があります。このような薬は絶対に猫の手の届かない場所に保管してください。

  • ​重篤な副作用​: これが強力な抗がん剤であることを理解してください。重度の胃腸障害、骨髄抑制（感染リスクの増加）、および神経症状を引き起こす可能性があります。
  • ​モニタリング​: ペットの白血球数が安全な範囲にあることを確認するため、血液検査（CBC）のための再診予約を厳守する必要があります。
  • ​家庭での安全性​: この薬は催奇形性物質（先天性欠損症を引き起こす可能性がある）として知られており、体液中に排泄されるため、妊婦、授乳中の母親、および子供は、治療後数日間は薬やペットの排泄物（尿/便）に触れないようにしてください。粗相を片付ける際は手袋を着用してください。

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