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メチオニン

Methionine

DL-Methionine, Racemethionine

尿酸性化薬 / 栄養補助食品POIVtopical犬猫馬牛

別名: Ammonil · Acimethin · Acimol · M-Caps · Methigel · Methio-Form · Methiotrans · Methnine · Neutrodor · Pedameth · Uracid · Uromethin · Uroeze · dl-methionine · racemethionine · s-methionine · methioninum

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

100 mg/kg PO q12hPO· q12h
— 🐕

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
Urine acidification (struvite dissolution)100 mg/kg PO q12hPOq12h—🌎 NA
Struvite dissolution therapy (if diet and antimicrobials do not result in acid urine)0.2-1 gram PO q8hPOq8h—🌎 NA
  • Urine acidification (struvite dissolution): Safe and effective in dissolving presumed infection-induced struvite uroliths in combination with an appropriate anti-microbial agent without using a struvite dissolution diet.

猫

適応用量経路頻度期間地域
Urine acidification1000-1500 mg per day given in the food once dailyPOq24h—🌎 NA
Urine acidification0.2-1 gram PO once dailyPOq24h—🌎 NA
  • Urine acidification: Use if diet and antimicrobials do not reduce pH.

馬

適応用量経路頻度期間地域
Laminitis (purported)22 mg/kg PO once daily for one week; then 11 mg/kg PO once daily for 1 week; then 5.5 mg/kg PO once daily for one weekPOq24h3 weeks🌎 NA
Senecio-induced liver damage12.5 grams IV in one liter saline/dextrose solutionIVOnce—🌎 NA

牛

適応用量経路頻度期間地域
General / Ketosis20-30 grams POPO——🌎 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。

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概要

​メチオニン (Methionine)​ は硫黄を含む必須アミノ酸であり、獣医学においては主に​尿酸性化薬​および栄養補助食品として使用されます。

  • ​尿酸性化：​ 尿のpHを低下させることで、​ストルバイト（リン酸アンモニウムマグネシウム）尿石​の溶解および予防に歴史的に使用されてきました。
  • ​臨床のポイント：​ 小動物においては、追加のサプリメントなしで尿pHを効果的に管理できる専用の処方食（s/d、c/dなど）にその役割がほぼ取って代わられています。
  • ​抗脂肪肝作用：​ コリン欠乏状態における脂肪肝を予防または改善する抗脂肪肝薬として機能します。
  • ​大動物での使用：​ 豚や家禽の栄養補助食品、牛のケトーシス治療、また馬や牛の蹄葉炎（蹄と蹄骨の結合を維持するためのジスルフィド結合基質を提供するとされる）の治療に推奨されることがありますが、蹄葉炎に対する明確な有効性の証拠は不足しています。

作用機序

Methionine exerts its effects through several metabolic pathways:

  • ​Urine Acidification:​ Methionine is metabolized in the liver, where its sulfur component is oxidized to sulfate. This sulfate is excreted by the kidneys as sulfuric acid → effectively lowering urine pH.
  • ​Lipotropic Action:​ Methionine supplies methyl groups to ethanolamine → forms choline, which is essential for lipid transport and metabolism in the liver, preventing hepatic lipidosis.
  • ​Antioxidant & Structural Precursor:​ Two molecules of methionine convert to one molecule of cysteine, a critical precursor for glutathione (a major endogenous antioxidant) and essential for disulfide bond formation in structural proteins (like keratin in hooves).

安全性・警告

禁忌

  • Renal failure
  • Pancreatic disease
  • Hepatic insufficiency
  • Preexisting acidosis
  • Oxalate or urate calculi
  • Kittens
  • Pre-existing metabolic acidosis
  • Severe liver disease or hepatic encephalopathy
  • Urate, cystine, or calcium oxalate urolithiasis
  • Young growing animals
  • Pregnant or nursing animals

有害事象

  • Gastrointestinal distress (nausea, vomiting)
  • Heinz-body hemolytic anemia (especially in cats)
  • Methemoglobinemia
  • Ataxia
  • Cyanosis
  • Metabolic acidosis
  • Gastrointestinal upset (nausea, vomiting, diarrhea)
  • Heinz body anemia (especially in cats at high doses)
  • Worsening of hepatic encephalopathy in patients with liver disease

注意事項

​Hepatic Warning:​ If used in patients with frank hepatic insufficiency, methionine can cause increased production of mercaptan-like compounds and intensify the signs of hepatic encephalopathy (dementia or coma).

  • ​Urolithiasis Risk:​ Do not give to animals with oxalate or urate calculi, as these stones thrive in acidic environments.
  • ​Dietary Overlap:​ Unmonitored use concurrently with an acidifying diet (e.g., s/d, c/d) may easily lead to severe metabolic acidosis and signs of overdose.
  • ​Age Restrictions:​ Strictly not recommended for use in kittens due to high susceptibility to toxicity.

医薬品相互作用

Aminoglycosides (gentamicin, amikacin)

Urine acidification may diminish the effectiveness of aminoglycosides in treating bacterial urinary tract infections, as they are more effective in an alkaline medium.

Erythromycin

Urine acidification may diminish the effectiveness of erythromycin in treating bacterial urinary tract infections.

Quinidine

Urine acidification may increase the renal excretion of quinidine, potentially lowering its systemic levels.

Other urinary acidifiers (e.g., ammonium chloride)Major

Additive acidification leading to severe metabolic acidosis

Urinary acidifying dietsMajor

Excessive lowering of urine pH and increased risk of metabolic acidosis

監視

  • Urine pH (goal of therapy is typically ≤6.5)
  • Blood pH (if signs of toxicity or metabolic acidosis are present)
  • CBC in cats (if exhibiting signs of toxicity, to check for Heinz-body anemia)
  • Complete Blood Count (CBC) to monitor for Heinz bodies, especially in cats
  • Acid-base status (blood gases) if overdosage is suspected
  • Liver function

薬物動態

半減期

猫Not well documented犬Not well documented

吸収

Well absorbed from the gastrointestinal tract.

分布

Widely distributed throughout the body tissues as it is an essential amino acid.

代謝

Metabolized in the liver to sulfate and urea.

消失

Excreted primarily by the kidneys into the urine.

過剰投与

​Feline Toxicity:​ Cats are particularly sensitive to methionine overdose.

  • When administered at a dose of 2 grams orally per day to mature cats, it caused anorexia, methemoglobinemia, Heinz body formation (with resultant hemolytic anemia), ataxia, and cyanosis.
  • ​Kittens:​ Methionine may be highly toxic to kittens who consume other cats' food to which methionine has been added.

​General Toxicity:​ Metabolic acidosis can occur with overdoses in any species, particularly when used in combination with an acidifying diet. No specific information was located on the treatment of methionine overdosage; treatment should be symptomatic and supportive (e.g., correcting acid-base imbalances).

製品

製剤

  • Chewable tablets
  • Oral powder
  • Oral gel
  • Capsules
  • Topical ointment, cream, lotion, pads
  • Oral: 500 mg tablets

動物用医薬品

  • Methionine Tablets: 200 mg and 500 mg (Ammonil®, DL-Methionine Tablets®)
  • Methionine Chewable Tablets: 500 mg (Methio-Form®)
  • Methionine Powder (d-l-methionine Powder)
  • Methionine Gel: 400 mg (8%) per 120.5 gram tube (Methigel®)
  • 500 mg tablets (General Sale)

ヒト用医薬品

  • Methionine Capsules: 500 mg
  • Topical Ointments, cream, lotion, pads and powder
  • Various OTC dietary supplements (typically 500 mg capsules/tablets)

規制ステータス

European Union✓ 承認済みEMA
🐕 Dogs🐈 Cats

Available as a general sale item.

United Kingdom✓ 承認済みVMD
🐕 Dogs🐈 Cats

Classified as general sale.

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

保管・安定性

Methionine should be stored at room temperature.

飼主向け情報

  • ​投与方法：​ 胃腸の不快感を軽減し効果を高めるため、この薬は食事と一緒に与えるか、ペットの食事に直接混ぜて与えてください。

  • ​重要な警告：​ 子猫には与えないでください。また、この薬が添加された成猫用のキャットフードに子猫が近づけないようにしてください。

  • ​食事に関する注意：​ 獣医師の特別な指示がない限り、この薬を処方された泌尿器系用療法食（s/dやc/dなど）と併用しないでください。血液の酸性度に危険な変化を引き起こす可能性があります。
  • ​獣医師への連絡のタイミング：​ 猫に脱力感、食欲不振、歩行のふらつき、または歯茎が青白い/青紫色になるなどの症状が見られた場合は、直ちに獣医師に連絡してください。

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。