アスピリン

Aspirin

Acetylsalicylic Acid

非ステロイド性抗炎症薬 (NSAID) / 血小板凝集抑制薬PO犬猫小型哺乳類フェレット鳥馬牛豚

別名: ASA · Bayer · Ecotrin · Bufferin · Ascriptin · Alka-Seltzer · Empirin · Halfprin · Aspirin BP · Acetylsalicylic acid · Acidum acetylsalicylicum · Salicylic acid acetate · Acetylsal acid · Polopiryna

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

10 mg/kg PO q12hPO· 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

犬

適応	用量	経路	頻度	期間	地域
For analgesia	10 mg/kg PO q12h	PO	q12h	—	🌎 NA
As an antiinflammatory/antirheumatic	25 mg/kg PO q8h	PO	q8h	—	🌎 NA
For antipyrexia	10 mg/kg PO twice daily	PO	twice daily	—	🌎 NA
Post-Adulticide therapy for heartworm disease	7-10 mg/kg PO once a day	PO	once a day	—	🌎 NA
For adjunctive therapy in IMHA (antithrombotic)	0.5 mg/kg PO twice daily	PO	twice daily	—	🌎 NA
For adjunctive therapy of glomerular disease (antithrombotic)	0.5 mg/kg PO q24h	PO	q24h	—	🌎 NA
For adjunctive therapy with azathioprine and glucocorticoids for immune-mediated hemolytic anemia	0.5 mg/kg PO once daily	PO	once daily	—	🌎 NA
As an analgesic/antiinflammatory prior to elective intraocular surgery	6.5 mg/kg two to three times daily	PO	two to three times daily	—	🌎 NA
Reduction of platelet aggregation (e.g. IMHA)	0.5-1 mg/kg	PO	q24h	—	🌍 EU
Analgesia, pyrexia, inflammation	10-20 mg/kg	PO	q12h	—	🌍 EU

For analgesia: Recommend using buffered varieties of aspirin in dogs.
For adjunctive therapy in IMHA (antithrombotic): At this low dose risk for gastric ulceration is low, but adding misoprostol may reduce the risk.
Reduction of platelet aggregation (e.g. IMHA): Alternatively 0.5 mg/kg p.o. q12h. Doses are anecdotal.
Analgesia, pyrexia, inflammation: Safety and efficacy of this dose has not been established.

猫

適応	用量	経路	頻度	期間	地域
For analgesia/antipyrexia/antiinflammatory	One 'baby' aspirin (81 mg) PO every 2-3 days	PO	every 2-3 days	—	🌎 NA
For analgesia/antipyrexia/antiinflammatory	10 mg/kg PO every other day	PO	every other day	—	🌎 NA
For analgesia/antipyrexia/antiinflammatory	10 mg/kg PO q48-72h in food	PO	q48-72h	—	🌎 NA
For prophylaxis of arterial thromboembolism (ATE)	5 mg (total dose) per cat PO q72hours (every 3rd day)	PO	q72h	—	🌎 NA
For prophylaxis of arterial thromboembolism	81 mg (total dose; one 'baby' aspirin) q72hours (every 3rd day)	PO	q72h	—	🌎 NA
For prevention of thromboembolism (High dose)	40 mg per cat PO q72h	PO	q72h	—	🌎 NA
For prevention of thromboembolism (Low dose)	5 mg per cat PO q72h	PO	q72h	—	🌎 NA
Reduction of platelet aggregation (low dose)	18.75 mg (1/4 of a 75 mg tablet) per average sized cat	PO	3 days a week	—	🌍 EU
Reduction of platelet aggregation (high dose)	75 mg per average sized cat	PO	3 days a week	—	🌍 EU
Reduction of platelet aggregation (very low dose)	0.5 mg/kg	PO	q24h	—	🌍 EU

For prophylaxis of arterial thromboembolism: Likely a weaker, but less expensive option than clopidogrel/LMWH. Recommended in all cats with atrial enlargement and cardiomyopathy.
Reduction of platelet aggregation (low dose): Safety and efficacy not fully evaluated.
Reduction of platelet aggregation (high dose): May be associated with a higher risk of GI side effects.
Reduction of platelet aggregation (very low dose): Suggested to inhibit platelet COX without preventing beneficial prostacyclin production.

小型哺乳類

適応	用量	経路	頻度	期間	地域
For low grade analgesia (Rabbits)	5-20 mg/kg PO once daily	PO	once daily	—	🌎 NA
General use (Mice, Rats, Gerbils, Hamsters)	100-150 mg/kg PO q4h	PO	q4h	—	🌎 NA
General use (Guinea pigs)	87 mg/kg PO	PO	once	—	🌎 NA

フェレット

適応	用量	経路	頻度	期間	地域
General use	10-20 mg/kg PO once daily	PO	once daily	—	🌎 NA

General use: Has short duration of activity in ferrets.

鳥

適応	用量	経路	頻度	期間	地域
General use	5 grams in 250 mL of water as sole water source	PO	continuous	—	🌎 NA

General use: Because of significant hydrolysis, solution should be freshly prepared every 12 hours if stored at room temperature or every 4 days if refrigerated at 5°C.

馬

適応	用量	経路	頻度	期間	地域
For analgesia (Mature Horses)	two to four 240 grain boluses PO	PO	once	—	🌎 NA
For analgesia (Foals)	one to two 240 grain boluses	PO	once	—	🌎 NA
For analgesia	25 mg/kg PO q12h initially, then 10 mg/kg once daily	PO	q12h initially, then once daily	—	🌎 NA
For analgesia	15-100 mg/kg PO once daily	PO	once daily	—	🌎 NA
For anti-platelet activity as an adjunctive treatment of laminitis	5-10 mg/kg PO q24-48 hours or 20 mg/kg PO every 4-5 days	PO	q24-48h or every 4-5 days	—	🌎 NA

For analgesia (Mature Horses): Allow animals to drink water after administration.
For analgesia (Foals): Allow animals to drink water after administration.

牛

適応	用量	経路	頻度	期間	地域
For analgesia/antipyrexia	100 mg/kg PO q12h	PO	q12h	—	🌎 NA
For analgesia/antipyrexia (Mature Cattle)	two to four 240 grain boluses PO	PO	once	—	🌎 NA
For analgesia/antipyrexia (Calves)	one to two 240 grain boluses	PO	once	—	🌎 NA

For analgesia/antipyrexia (Mature Cattle): Allow animals to drink water after administration.
For analgesia/antipyrexia (Calves): Allow animals to drink water after administration.

豚

適応	用量	経路	頻度	期間	地域
For analgesia	10 mg/kg q4h PO	PO	q4h	—	🌎 NA
For analgesia	10 mg/kg q6h PO	PO	q6h	—	🌎 NA

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

アスピリン（アセチルサリチル酸）は、鎮痛、解熱、抗炎症作用を持ち、多くの獣医種で使用される古典的な非ステロイド性抗炎症薬（NSAID）です。

疼痛管理に加えて、アスピリンは抗血小板作用があるため、獣医学において独自の価値を持っています。犬（免疫介在性溶血性貧血、犬糸状虫症、糸球体疾患など）や猫（肥大型心筋症に続発する動脈血栓塞栓症の予防など）において、抗血栓薬として頻繁に使用されます。

臨床上のポイント： 猫へのアスピリン投与は細心の注意を払う必要があります。猫はサリチル酸の代謝に関与する肝酵素であるグルクロニルトランスフェラーゼが相対的に欠乏しています。これにより半減期が大幅に延長し（犬の約8時間に対し、猫では最大45時間）、投与頻度が高すぎると致命的な蓄積や中毒を引き起こす可能性が非常に高くなります。

作用機序

Aspirin exerts its effects primarily through the irreversible inhibition of cyclooxygenase (COX) enzymes, with a strong affinity for COX-1.

Anti-inflammatory & Analgesic: Inhibits COX-1 (and to a lesser extent COX-2) → decreases synthesis of pro-inflammatory prostaglandins.
Antiplatelet Effect: Irreversibly acetylates COX-1 in platelets → blocks the synthesis of Thromboxane A2 (TXA2), a potent inducer of platelet aggregation and vasoconstriction. Because platelets lack a nucleus, they cannot synthesize new COX enzymes; thus, the antiplatelet effect lasts for the lifespan of the platelet (typically 7-10 days).
Gastric Protection Modulator: While aspirin does not directly inhibit COX-2, it modifies it to interact with lipoxygenase (LOX) → produces aspirin-triggered lipoxin (ATL), which provides some gastric mucosal protective actions, potentially explaining why gastric damage may decrease with chronic use.

安全性・警告

禁忌

Known hypersensitivity to salicylates
Active gastrointestinal bleeding or ulcers
Bleeding disorders (relative contraindication)
Asthma (relative contraindication)
Renal insufficiency (relative contraindication)
Pregnancy (especially later stages; low-grade teratogen and may delay labor)

有害事象

Gastric irritation (nausea, anorexia, vomiting)
Gastrointestinal ulceration and occult blood loss
Secondary anemia or hypoproteinemia (due to chronic GI blood loss)
Metabolic acidosis (especially in cats)
Hypersensitivity reactions (rare in dogs)

注意事項

Hepatic and Renal Function: Use with extreme caution and enhanced monitoring in patients with severe hepatic failure or diminished renal function.

Hypoalbuminemia: Because aspirin is highly protein-bound, patients with low albumin may require lower dosages to prevent toxicity from increased free drug levels.

Surgical Procedures: Due to irreversible platelet inhibition, aspirin therapy should ideally be halted one week prior to elective surgical procedures to prevent excessive bleeding.

Species Specifics: Must be used with extreme caution in cats due to their inability to rapidly metabolize salicylates. Use cautiously in neonatal animals, as adult doses may lead to toxicity.

医薬品相互作用

Alkalinizing drugs (e.g., sodium bicarbonate, acetazolamide)

Significantly increases the renal excretion of salicylates; carbonic anhydrase inhibitors may cause systemic acidosis and increase CNS salicylate levels, leading to toxicity.

AminoglycosidesMajor

May increase the likelihood of nephrotoxicity.

Corticosteroids

May increase salicylate clearance (decreasing serum levels) and significantly increase the risk of gastrointestinal ulceration and bleeding.

Digoxin

Aspirin may increase plasma levels of digoxin by decreasing its clearance.

Furosemide

May compete with renal excretion of aspirin, delaying its elimination and potentially causing toxicity at high doses.

Heparin or Oral Anticoagulants

Increased risk of bleeding due to synergistic antiplatelet/anticoagulant effects.

Methotrexate

Aspirin may displace methotrexate from plasma proteins, increasing the risk of methotrexate toxicity.

Other NSAIDsMajor

Increased risk of severe GI ulceration. A washout period of 3-10 days is recommended when switching from aspirin to a COX-2 selective NSAID.

Phenobarbital

May increase the rate of aspirin metabolism by inducing hepatic enzymes.

Probenecid, Sulfinpyrazone

Aspirin may antagonize the uricosuric effects of these drugs.

Spironolactone

Aspirin may inhibit the diuretic activity of spironolactone.

Tetracycline

Antacids in buffered aspirin may chelate tetracyclines; separate doses by at least one hour.

Urinary Acidifying Drugs (methionine, ammonium chloride, ascorbic acid)

Can decrease the urinary excretion of salicylates, potentially leading to accumulation.

GlucocorticoidsMajor

Increased risk of GI ulceration. Do not administer concurrently (Exception: specific protocols for IMHA treatment).

監視

Analgesic and/or antipyretic efficacy
Bleeding times (if indicated)
Packed Cell Volume (PCV)
Stool guaiac tests (for occult GI bleeding)
Acid-base status (in cases of overdose)

薬物動態

半減期

猫27-45 hours犬~8 hours

吸収

Rapidly absorbed from the stomach and proximal small intestine in monogastric animals. Absorption is slow from the GI tract in cattle, but approximately 70% of an oral dose is absorbed.

分布

Widely distributed throughout the body. Highest levels in liver, heart, lungs, renal cortex, and plasma. Highly protein bound (90% at lower concentrations, 70% at higher concentrations). Crosses the placenta and is excreted in milk.

代謝

Metabolized in the liver primarily by conjugation with glycine and glucuronic acid via glucuronyl transferase. Cats are deficient in this pathway, leading to prolonged half-lives and susceptibility to accumulation.

消失

Rapidly excreted by the kidneys via both filtration and renal tubular secretion. Excretion is highly pH dependent and can be significantly increased by raising urine pH to 5-8.

過剰投与

Clinical Signs of Acute Toxicity:

Early signs: Depression, vomiting (may be blood-tinged), anorexia, hyperthermia, panting/increased respiratory rate.
Acid-Base Disturbances: Initially, a respiratory alkalosis occurs due to hyperventilation, followed by a profound metabolic acidosis.
Severe signs: Muscular weakness, pulmonary and cerebral edema, hypernatremia, hypokalemia, ataxia, seizures, coma, and death.

Treatment Protocol:

Decontamination: Emesis (if within 12 hours of ingestion), activated charcoal, and an oral cathartic. Gastric lavage with 3-5% sodium bicarbonate may delay absorption.
Fluid Therapy: IV fluids (e.g., Dextrose 5% in water) to correct dehydration.
Alkaline Diuresis: Forced alkaline diuresis with sodium bicarbonate enhances renal excretion, but should only be attempted if acid-base status can be monitored. Mannitol (1-2 g/kg/hr) may enhance diuresis.
Supportive Care: GI protectants. Control seizures with IV diazepam.
Coagulopathy Management: Phytonadione (Vitamin K1) at 2.5 mg/kg divided q8-12h and ascorbic acid (though ascorbic acid may negate urinary alkalinization).
Heroic Measures: Peritoneal dialysis or exchange transfusions in severe cases.

製品

製剤

Tablets (plain, enteric-coated, chewable, buffered)
Extended-release tablets
Boluses (240 grain, 480 grain)
Oral gel
Powder
Granules
Liquid concentrate

動物用医薬品

Aspirin Tablets (Enteric-Coated): 81 mg
Aspirin Tablets (Buffered, Microencapsulated, Chewable for dogs): 150 mg & 450 mg
Aspirin Tablets 60 grain (3.9 g)
Aspirin Boluses 240 grain (15.6 g)
Aspirin Boluses 480 grain (31.2 g)
Oral Aspirin Gel: 250 mg/mL and 500 mg/mL
Aspirin Powder: 50% acetylsalicylic acid in base
Aspirin Granules: 2.5 gram per 39 mL scoop
Aspirin Liquid Concentrate (equiv to 12% aspirin)

ヒト用医薬品

Aspirin Chewable Tablets: 81 mg
Aspirin Tablets (plain uncoated): 325 mg & 500 mg
Aspirin Tablets (enteric coated): 81 mg, 165 mg, 325 mg, 500 mg, 650 mg, & 800 mg
Aspirin Extended-controlled Release Tablets: 81 mg, 650 mg, 800 mg & 975 mg
Aspirin Tablets (buffered uncoated): 325 mg & 500 mg
Aspirin Tablets (buffered coated): 325 mg & 500 mg

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

🐕 Dogs🐈 Cats

Available as human generic (Aspirin BP) and component of many others.

United Kingdom✓ 承認済み処方箋医薬品VMD

🐕 Dogs🐈 Cats

Available as human generic (Aspirin BP) and component of many others.

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

保管・安定性

Store tablets in tight, moisture-resistant containers. Aspirin is stable in dry air but readily hydrolyzes to acetate and salicylate when exposed to water or moist air. Do not use if a strong vinegar-like odor is noted, as this indicates degradation.

飼主向け情報

出血に注意： 黒色タール便、コーヒーかすのような嘔吐物、食欲不振、重度の無気力など、胃潰瘍や出血の兆候が見られた場合は、直ちに獣医師に連絡してください。
厳格な用量遵守： 処方された以上のアスピリンを与えたり、投与頻度を増やしたりしないでください。これは猫にとって特に重要です。猫はアスピリンの代謝が非常に遅く、標準的な人間用の用量でも容易に致命的な中毒を引き起こす可能性があります。
食肉・搾乳動物の休薬期間： FDAによる公式な休薬期間の規定はありませんが、サリチル酸に敏感な人々を保護するため、乳や肉の摂取には最低1日間の休薬期間を設けることが推奨されます。

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。