スピロノラクトン

Spironolactone

アルドステロン拮抗薬 / カリウム保持性利尿薬PO犬猫

別名: Aldactone · Aldactazide · Cardalis · Prilactone · espironolactona · SC-9420 · spirolactone · spironolactonum

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

1-2 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
As a diuretic in CHF (when furosemide and ACE inhibitors alone do not control fluid accumulation)	1-2 mg/kg PO q12h	PO	q12h	—	🌎 NA
As a diuretic in CHF (with other diuretics when hypokalemia is an issue)	2-4 mg/kg PO once daily	PO	q24h	—	🌎 NA
As a diuretic in CHF (to allow further reduction of furosemide dose)	0.5 mg/kg PO once daily to 2 mg/kg twice daily	PO	q24h to q12h	—	🌎 NA
For treating ascites (using fixed dose combination with hydrochlorothiazide)	0.5-1 mg/kg PO twice daily	PO	q12h	—	🌎 NA
For treating ascites (caused by right-sided heart failure)	1-2 mg/kg PO q12h	PO	q12h	—	🌎 NA
For adjunctive treatment of hypertension	1-2 mg/kg PO q12h	PO	q12h	—	🌎 NA
For adjunctive treatment of hypertension (Step 4 drug)	1-2 mg/kg twice daily	PO	q12h	—	🌎 NA
Congestive heart failure, ascites, hyperaldosteronism	2-4 mg/kg	PO	q24h	Continuous	🌍 EU

As a diuretic in CHF (when furosemide and ACE inhibitors alone do not control fluid accumulation): Refractory CHF
As a diuretic in CHF (to allow further reduction of furosemide dose): 0.5 mg/kg once daily for aldosterone blockage (weak diuretic effect); 2 mg/kg twice daily for stronger diuretic effect.
For treating ascites (using fixed dose combination with hydrochlorothiazide): Empirical dosage based on the spironolactone component of Aldactazide.
For treating ascites (caused by right-sided heart failure): Added to optimized furosemide and ACE inhibitor therapy.
For adjunctive treatment of hypertension (Step 4 drug): For systolic >160 mmHg, diastolic >120 mmHg after enalapril/benazepril and amlodipine.
Congestive heart failure, ascites, hyperaldosteronism: Licensed for use in combination with standard therapy for treatment of CHF caused by valvular regurgitation in dogs.

猫

適応	用量	経路	頻度	期間	地域
As a diuretic in CHF (when furosemide and ACE inhibitors alone do not control fluid accumulation)	1-2 mg/kg PO q12h	PO	q12h	—	🌎 NA
As a diuretic in CHF (when serum potassium is low)	1 mg/kg q12h PO	PO	q12h	—	🌎 NA
For adjunctive treatment of hypertension	1-2 mg/kg PO q12h	PO	q12h	—	🌎 NA
For adjunctive treatment of hypertension (Step 3 drug)	1-2 mg/kg twice daily	PO	q12h	—	🌎 NA
For adjunctive treatment of primary hyperaldosteronism	1-2 mg/kg PO twice daily	PO	q12h	—	🌎 NA
Congestive heart failure, ascites, hyperaldosteronism	2-4 mg/kg	PO	q24h	Continuous	🌍 EU

As a diuretic in CHF (when furosemide and ACE inhibitors alone do not control fluid accumulation): Refractory CHF
For adjunctive treatment of hypertension (Step 3 drug): When systolic BP >160 mmHg, diastolic >120 mmHg after amlodipine and ACE inhibitor.
For adjunctive treatment of primary hyperaldosteronism: If potassium supplementation alone does not control clinical signs.
Congestive heart failure, ascites, hyperaldosteronism: Severe ulcerative facial dermatitis has been reported in Maine Coon 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

スピロノラクトンは合成アルドステロン拮抗薬およびカリウム保持性利尿薬です。獣医療では主に、うっ血性心不全（CHF）、腹水、全身性高血圧、および原発性アルドステロン症（特に猫）の補助治療として使用されます。

臨床のポイントと薬理学的背景:

アルドステロン・ブレイクスルー: フロセミドなどのループ利尿薬に比べて直接的な利尿効果は弱いものの、レニン・アンジオテンシン・アルドステロン系（RAAS）の阻害において重要な役割を果たします。ACE阻害薬を服用していても、最終的にアルドステロン値が再び上昇する現象（アルドステロン・ブレイクスルー）を防ぐ効果があります。
心筋保護作用: 人医療では、心筋の線維化を防ぎ、有害な心臓リモデリングを予防する効果が高く評価されています。獣医療（粘液腫様僧帽弁疾患の犬など）におけるこの効果の程度については議論がありますが、標準的なCHFの多剤併用プロトコルに組み込まれることが増えています。
バイオアベイラビリティ: 食事と一緒に投与することで吸収が大幅に向上します。

作用機序

Spironolactone acts as a competitive antagonist at the mineralocorticoid receptor.

Mechanism: It competitively inhibits aldosterone binding in the distal renal tubules and collecting ducts.
Pathway: Blockade of the receptor → prevents the synthesis of aldosterone-induced proteins (such as Na+/K+ ATPase and epithelial sodium channels) → decreases sodium and chloride reabsorption while decreasing potassium, ammonium, and phosphate excretion.
Result: Mild diuresis with potassium retention. It does not affect carbonic anhydrase or proximal renal transport mechanisms.

安全性・警告

禁忌

Hyperkalemia
Addison's disease (hypoadrenocorticism)
Anuria
Acute renal failure
Significant renal impairment
Hyperkalaemia
Hyponatraemia
Concurrent use with NSAIDs in animals with renal insufficiency
Pregnancy
Lactation
Animals intended for breeding

有害事象

Facial dermatitis (notably reported in Maine Coon cats)
Hyperkalemia
Hyponatremia
Dehydration
Increased BUN and mild acidosis (in patients with renal impairment)
Gastrointestinal distress (vomiting, anorexia)
CNS effects (lethargy, ataxia)
Endocrine changes (anti-androgenic effects, e.g., gynecomastia in humans, feminization of male fetuses)
Hyponatraemia
Hyperkalaemia
Reversible prostatic atrophy (in entire male dogs)
Severe ulcerative facial dermatitis (in Maine Coon cats)
Hepatotoxicity (reported in humans)

注意事項

Hepatic & Renal Caution: Use cautiously in patients with hepatic disease (though often used to treat ascites). Use in patients with renal impairment may lead to hyperkalemia.

Reproductive Safety: FDA Category D for pregnancy. Spironolactone and its active metabolites cross the placenta and can cause feminization of male fetuses. Canrenone (active metabolite) is excreted in breast milk; use with caution in nursing animals.

医薬品相互作用

DigoxinModerate

Spironolactone may increase the half-life of digoxin; enhanced monitoring of digoxin serum levels is warranted. May also cause falsely elevated digoxin values if using a radioimmune assay (RIA).

Mitotane

Spironolactone may mute the effects of mitotane if given concurrently; monitor carefully.

Neuromuscular blockers, non-depolarizing

Possible increase in neuromuscular blockade effects.

Potassium-sparing diuretics (e.g., triamterene)

Increased risk of hyperkalemia.

Potassium supplementsMajor

Increased risk of hyperkalemia.

Salicylates (e.g., Aspirin)

Spironolactone's diuretic effects may be decreased if administered concomitantly.

Thiazide diureticsModerate

Potentiates diuretic effects

Loop diureticsModerate

Potentiates diuretic effects

ACE inhibitorsModerate

Increased risk of hyperkalaemia (though generally safe to use concurrently in practice; monitor potassium)

NSAIDsMajor

Increased risk of hyperkalaemia and nephrotoxicity

CiclosporinModerate

Increased risk of hyperkalaemia

監視

Serum electrolytes (especially potassium and sodium)
BUN and creatinine
Hydration status
Blood pressure (if indicated)
Clinical signs of edema/ascites
Patient weight
Serum potassium
Serum sodium
Renal function (BUN, Creatinine)
Digoxin levels (if used concurrently)

薬物動態

半減期

犬Spironolactone: 1-2 hours; Canrenone (active metabolite): ~20 hours

吸収

In fasted dogs, oral bioavailability is approximately 50%, but increases up to 90% when given with food. In humans, it is >90% bioavailable with peak levels reached within 1-2 hours.

分布

Spironolactone and its active metabolite, canrenone, are both about 98% bound to plasma proteins. Both cross the placenta, and canrenone is detected in breast milk.

代謝

Rapidly metabolized to several metabolites, including the active metabolite canrenone, which possesses diuretic activity.

消失

About 70% of a dose is found in the feces and 18% in the urine.

過剰投与

Information on acute overdosage of spironolactone in veterinary patients is limited.

Management: Should an acute overdose occur, follow general guidelines for diuretic overdose (e.g., furosemide or chlorothiazide).
Treatment: Empty the stomach if ingestion was recent. Provide supportive care, monitor hydration status, and closely evaluate serum electrolytes (especially potassium and sodium).
Contact an animal poison control center for further guidance.

製品

製剤

Oral tablets
Oral suspension (compounded)
10 mg tablet
40 mg tablet
50 mg tablet
80 mg tablet
100 mg tablet
Compound preparations with benazepril (e.g., 2.5mg/20mg, 5mg/40mg, 10mg/80mg)

動物用医薬品

Cardalis (compound with benazepril)
Prilactone

ヒト用医薬品

Spironolactone Oral Tablets: 25 mg, 50 mg & 100 mg; Aldactone® (Searle); generic
Spironolactone/Hydrochlorothiazide Oral Tablets: 25 mg/25 mg & 50 mg/50 mg; Aldactazide® (Searle); generic
Spironolactone generics

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA

🐕 Dogs

POM-V / POM

United Kingdom✓ 承認済み処方箋医薬品VMD