VetSheet

ナプロキセン

Naproxen

非ステロイド性抗炎症薬 (NSAID)POIV犬小型哺乳類馬

別名: Aleve · Anaprox · EC-Naprosyn · Midol Extended Relief · Naprelan · Equiproxen · naproxeneum · RS-3540 · RS-3650 · naproxen sodium

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

2 mg/kg PO every other day (q48h)PO· q48h
— 🐕

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
Osteoarthritis and musculoskeletal inflammatory diseases (Last resort)2 mg/kg PO every other day (q48h)POq48h—🌎 NA
  • Osteoarthritis and musculoskeletal inflammatory diseases (Last resort): Because of the difficulty in accurately dosing naproxen and its potential for adverse effects, use only when FDA-approved and safer NSAIDs have been ineffective.

小型哺乳類

適応用量経路頻度期間地域
Septic arthritis pain; inflammation (Rabbits)2.4 mg/mL in drinking water for 21 daysPOContinuous21 days🌎 NA
  • Septic arthritis pain; inflammation (Rabbits): Dose specific to rabbits.

馬

適応用量経路頻度期間地域
Myositis and soft tissue diseases of the musculoskeletal system5 mg/kg by slow IV, then 10 mg/kg, PO (top dressed in feed) twice daily for up to 14 days or 10 mg/kg, PO (top dressed in feed) twice daily for up to 14 consecutive days.IV, POq12hUp to 14 days🌎 NA
Systemic therapies for joint disease10 mg/kg PO dailyPOq24h—🌎 NA
  • Myositis and soft tissue diseases of the musculoskeletal system: ARCI UCGFS Class 4 Drug. Veterinary product no longer commercially available.

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

ナプロキセンは、プロピオン酸系に属する​非ステロイド性抗炎症薬（NSAID）​であり、構造的にイブプロフェンやケトプロフェンに似ています。

  • ​獣医療での使用​：獣医療での使用は、より新しく安全でCOX-2選択性の高いNSAIDにほぼ取って代わられています。
  • ​毒性のリスク​：犬においては半減期が非常に長く（74時間）、広範な腸肝循環を伴うため、治療域が非常に狭く、毒性が高いことで知られています。多くの臨床医は犬への使用を強く推奨していません。
  • ​馬での使用​：以前は馬の筋骨格系の痛み、筋炎、軟部組織疾患に使用されていましたが、獣医専用製品（Equiproxen®）は米国ではすでに販売されていません。

作用機序

Naproxen exerts its analgesic, anti-inflammatory, and antipyretic effects by inhibiting the ​cyclooxygenase (COX)​ enzymes.

  • Arachidonic Acid → COX-1 and COX-2 inhibition → Decreased synthesis of prostaglandins and thromboxanes.
  • The reduction in pro-inflammatory prostaglandins mitigates inflammation, pain, and fever.
  • Because naproxen is a non-selective COX inhibitor, it also blocks the constitutive, protective prostaglandins (via COX-1) in the gastric mucosa and kidneys. This mechanism explains its high propensity for causing gastrointestinal ulceration and renal toxicity, particularly in sensitive species like dogs and cats.

安全性・警告

禁忌

  • Active GI ulcers
  • History of hypersensitivity to naproxen or other NSAIDs
  • Pre-existing hematologic, renal, or hepatic disease

有害事象

  • GI distress (anorexia, vomiting, diarrhea)
  • Gastrointestinal ulcers and perforation
  • Melena and bloody vomitus
  • Renal effects (nephritis, nephrotic syndrome, fluid retention)
  • Hepatic effects (increased liver enzymes)
  • Hematologic effects (hypoproteinemia, decreased hematocrit, anemia)
  • CNS effects (neuropathies, lethargy, depression)

注意事項

WARNING: Extremely narrow therapeutic index in dogs. Use is generally discouraged unless all FDA-approved, safer NSAIDs have failed.

  • Relatively Contraindicated: Patients with a history of or pre-existing hematologic, renal, or hepatic disease.
  • Caution: Use cautiously in patients with a history of GI ulcers or heart failure (may cause fluid retention).
  • Infection: Animals suffering from inflammation secondary to concomitant infection should receive appropriate antimicrobial therapy alongside NSAID treatment.

医薬品相互作用

Aminoglycosides (gentamicin, amikacin)

Increased risk for nephrotoxicity

Anticoagulants (heparin, LMWH, warfarin)

Increased risk for bleeding

Aspirin

Decreased plasma levels of naproxen and increased likelihood of GI adverse effects (blood loss). Concomitant use is not recommended.

Bisphosphonates (alendronate)

May increase risk for GI ulceration

Corticosteroids

Concomitant administration significantly increases the risks for GI adverse effects and ulceration

Furosemide

Naproxen may reduce the saluretic and diuretic effects of furosemide

Highly protein bound drugs (phenytoin, valproic acid, sulfonamides)

Potential displacement leading to increased serum levels and duration of action of the displaced drug

Methotrexate

Serious toxicity has occurred; use together with extreme caution

Probenecid

May cause a significant increase in serum levels and half-life of naproxen

監視

  • Analgesic/anti-inflammatory efficacy
  • GI signs: appetite, feces (occult blood, diarrhea)
  • PCV (packed cell volume) and hematocrit if indicated or on chronic therapy
  • WBCs if indicated or on chronic therapy
  • Renal and hepatic function panels (especially in dogs)

薬物動態

半減期

馬~4 hours犬74 hours

吸収

Horses: 50% bioavailability after oral dosing; absorption is not altered by food. Dogs: Rapid oral absorption with 68-100% bioavailability.

分布

Highly bound to plasma proteins (99% in humans). Crosses the placenta and enters milk at about 1% of serum levels.

代謝

Metabolized in the liver.

消失

Detectable in the urine for at least 48 hours in the horse after an oral dose.

過剰投与

Toxicity is a major concern, particularly in dogs and cats.

  • Dogs: The reported oral LD50 is >1000 mg/kg, but clinical toxicity occurs at much lower doses.
    • ​>5 mg/kg​: Gastrointestinal signs and GI ulceration.
    • ​>25 mg/kg​ (some dogs as low as 10 mg/kg): Significant renal damage.
    • ​>50 mg/kg​: Neurologic signs.
  • Clinical Signs: Vomiting (often bloody), lethargy, anorexia, diarrhea, melena, anemia, and elevated renal/hepatic values.
  • Treatment:
    • Decontamination: Emesis and/or activated charcoal if recent ingestion.
    • GI Protection: Misoprostol and sucralfate are recommended for 10-14 days post-exposure.
    • Renal Protection: Fluid diuresis should be considered if renal effects are expected.
    • Supportive Care: Monitor electrolyte and fluid balance carefully; manage renal failure using established guidelines.

製品

製剤

  • Oral tablets
  • Gelcaps
  • Capsules
  • Delayed/controlled-release tablets
  • Oral suspension
  • Injection (historically available for horses)

動物用医薬品

  • None currently marketed in the USA (Equiproxen® is discontinued)

ヒト用医薬品

  • Naproxen Oral Tablets/Gelcaps/Capsules: 200 mg, 250 mg, 375 mg, 500 mg
  • Naproxen Delayed/Controlled-release Tablets: 375 mg, 500 mg, 750 mg
  • Naproxen Oral Suspension: 125 mg/5 mL

規制ステータス

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

保管・安定性

Store in well-closed, light-resistant containers at room temperature. Avoid temperatures above 40°C (104°F).

飼主向け情報

​危険​：獣医師の明確な指示なしに、Aleve®などの人間用市販鎮痛薬をペットに絶対に与えないでください。ナプロキセンは犬や猫に対して非常に強い毒性を持っています。

  • ペットにナプロキセンが処方された場合は、投薬スケジュール（犬の場合は1日おきなど）を厳密に守ってください。
  • 以下の症状に気づいた場合は、​直ちに投薬を中止し、獣医師に連絡してください​：
    • 食欲不振や無気力・うつ状態
    • 嘔吐（特に血が混じっている場合やコーヒーの粉のように見える場合）
    • 下痢や黒色タール便
    • 飲水や排尿の習慣の変化

VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。