ファムシクロビル

Famciclovir

Purine-derived, synthetic, acyclic purine nucleoside analog

抗ウイルス薬（ヘルペス）PO猫

別名: Famvir · AV 42810 · BRL 42810 · famciclovirum

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

90 mg/kgPO· q12h

体重— 🐈

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

猫

適応	用量	経路	頻度	期間	地域
Feline herpes virus (FHV-1)	125 mg (total dose)	PO	2-3 times a day	—	🌎 NA
Adjunctive treatment of FHV-1 rhinotracheitis	31.25 mg (1/4 of one 125 mg tablet)	PO	q12h	14 days	🌎 NA
Chronic, recurrent and/or severe herpes viral infection	Kittens: 1/8th of one 125 mg tablet; adult cats: 1/4 of one 250 mg tablet	PO	once daily (q24h)	Kittens: 2 weeks; adult cats: 3 weeks	🌎 NA
Feline herpes virus (FHV-1)	1/4 of one 125 mg tablet	PO	twice daily (q12h)	10-14 days; may continue once daily for up to 30 days	🌎 NA
Adjunctive treatment (with interferon and lysine) of herpes virus-associated ulcerative facial dermatitis & stomatitis	125 mg	PO	q12h	—	🌎 NA
Management of feline herpesvirus (FHV-1) infections	90 mg/kg	PO	q12h	—	🌍 EU

Feline herpes virus (FHV-1): Author's choice. Wide range of doses used.
Adjunctive treatment of FHV-1 rhinotracheitis: Has not been evaluated for longterm therapy.
Chronic, recurrent and/or severe herpes viral infection: Dose range is variable!
Management of feline herpesvirus (FHV-1) infections: Dose recommendations have varied because of complex and non-linear pharmacokinetics in cats.

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

ファムシクロビルは、獣医療において主に猫ヘルペスウイルス1型（FHV-1）感染症の治療に使用される経口抗ウイルス薬です。

体内で抗ウイルス活性を持つペンシクロビルに変換されるプロドラッグです。
猫はこの変換を担う肝アルデヒドオキシダーゼのレベルが非常に低いため、治療濃度に達するにはヒトや他の動物と比較してかなり高用量を必要とすることがよくあります。
猫における短期使用（2〜3週間）では一般的に忍容性が良好ですが、長期的な安全性データはまだ限られています。
臨床のポイント: 比較的高価ですが、ジェネリック医薬品の普及により、重度または難治性のFHV-1症例にとって利用しやすい選択肢となっています。

作用機序

Famciclovir is a prodrug that undergoes biotransformation to become active: Famciclovir → hepatic aldehyde oxidase → Penciclovir

Once inside a virus-infected cell: Penciclovir → viral thymidine kinase → Penciclovir monophosphate → cellular kinases → Penciclovir triphosphate

The triphosphate form competes with deoxyguanosine triphosphate to inhibit herpes virus DNA polymerase.
This selectively and effectively halts herpes viral DNA synthesis and replication.
Viral resistance can occur via mutation.

安全性・警告

禁忌

Known hypersensitivity to famciclovir or penciclovir

有害事象

Cats: Anorexia and polydipsia (noted at high doses of 90 mg/kg PO q8h)
Humans: Nausea, vomiting, diarrhea, headache, neutropenia, renal failure
Gastrointestinal signs (vomiting, diarrhea, anorexia)

注意事項

Caution in Renal Impairment: Famciclovir is primarily excreted by the kidneys. Dosage adjustments are highly recommended for patients with renal dysfunction (e.g., CrCl < 40 mL/min in humans).

Pregnancy/Nursing: FDA Category B in humans. Animal studies up to 1,000 mg/kg/day showed no embryo/fetal effects. Excreted in the milk of rats; clinical significance for nursing offspring is unclear.

医薬品相互作用

Probenecid

Can reduce the amount of penciclovir excreted by the kidneys, leading to increased penciclovir plasma levels

監視

Clinical efficacy (resolution of ocular/respiratory signs)
Adverse effects (most likely GI upset, anorexia, polydipsia)
Consider occasional CBCs and serum creatinine to monitor for neutropenia or renal dysfunction if using the drug chronically
Haematology
Biochemistry
Urinalysis (especially in cats with concurrent disease or on long-term therapy)

薬物動態

吸収

In humans, well absorbed orally but undergoes extensive first-pass metabolism. Food decreases peak levels but does not impact clinical efficacy. In cats, pharmacokinetics are complex; after 62.5 mg PO, penciclovir peak levels were less than the in vitro IC-50 for FHV-1.

分布

Penciclovir (active metabolite) is only marginally bound to plasma proteins.

代謝

Converted to penciclovir. In humans, requires oxidation by hepatic aldehyde oxidase. Cats possess little hepatic aldehyde oxidase, necessitating higher dosages.

消失

Excretion is primarily via renal mechanisms.

過剰投与

Little information is available regarding acute toxicity. Supportive treatment is recommended. Penciclovir can be removed by hemodialysis.

製品

製剤

Oral Tablets (film-coated): 125 mg, 250 mg, 500 mg
125 mg tablet
250 mg tablet
500 mg tablet
100 mg/ml oral paste

動物用医薬品

100 mg/ml oral paste (often compounded or specific to certain markets)

ヒト用医薬品

Famciclovir Oral Tablets (film-coated) 125 mg, 250 mg, & 500 mg: Famvir (Novartis); generic
Famvir 125 mg tablets
Famvir 250 mg tablets
Famvir 500 mg tablets

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

POM (Prescription Only Medicine)

United Kingdom✓ 承認済み処方箋医薬品VMD