水酸化マグネシウム

Magnesium Hydroxide

Magnesium hydroxide

別名: Milk of Magnesia · Magnalax · Carmilax · Polymag · Rumen Bolus · Instamag · Polyox · Laxade · Maalox · Phillips' Chewable · Magnesium/Aluminum Antacids

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

5-15 mL/per dog per 24 hoursPO· q24h

5–15 ml — 個体ごとの固定用量（体重換算なし）

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
Adjunctive treatment of hypomagnesemia with GI disease and severe hypocalcemia	5-15 mL/per dog per 24 hours	PO	q24h	—	🌎 NA
Adjunctive therapy for gastric ulcers	2-10 mL PO q2-4h	PO	q2-4h	—	🌎 NA
Antacid	5-30 mL PO once to twice daily	PO	q12-24h	—	🌎 NA

Adjunctive treatment of hypomagnesemia with GI disease and severe hypocalcemia: Using Milk of Magnesia
Adjunctive therapy for gastric ulcers: Using Aluminum hydroxide suspension or aluminum hydroxide/magnesium hydroxide suspension
Antacid: Using Milk of Magnesia

猫

適応	用量	経路	頻度	期間	地域
Antacid	5-15 mL PO once to twice daily	PO	q12-24h	—	🌎 NA

Antacid: Using Milk of Magnesia

馬

適応	用量	経路	頻度	期間	地域
Adjunctive gastroduodenal ulcer therapy in foals	15 mL 4 times a day	PO	q6h	—	🌎 NA

Adjunctive gastroduodenal ulcer therapy in foals: Using Aluminum/magnesium hydroxide suspension

牛

適応	用量	経路	頻度	期間	地域
Rumen overload syndrome (Adults)	Up to 1 gram/kg (MgOH) mixed in 2-3 gallons of warm water and given PO per tube. May repeat (use smaller doses) at 612 hour intervals. If the rumen has been evacuated, do not exceed 225 grams initially.	PO	q6-12h	—	🌎 NA
Rumen overload syndrome (Calves)	As above but use ⅛th-¼th the amount	PO	q6-12h	—	🌎 NA

Rumen overload syndrome (Adults): Dehydration and systemic acidosis must be concomitantly corrected.

羊

適応	用量	経路	頻度	期間	地域
Rumen overload syndrome	As above for cattle, but use ⅛th-¼th the amount	PO	q6-12h	—	🌎 NA

ヤギ

適応	用量	経路	頻度	期間	地域
Rumen overload syndrome	As above for cattle, but use ⅛th-¼th the amount	PO	q6-12h	—	🌎 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

水酸化マグネシウムは獣医学において経口制酸剤および下剤として使用されます。小動物では胃酸過多や潰瘍の治療に使用されてきましたが、現在ではより効果的な薬剤に取って代わられています。反芻動物では、第一胃過負荷症候群（第一胃アシドーシス）の治療において、粉末製剤が非常に効果的です。

作用機序

Acts locally in the gastrointestinal tract:

Antacid: Neutralizes gastric hydrochloric acid (HCl) → raises gastric pH. Raising pH >4 minimizes pepsin proteolytic activity, reducing gastric mucosal damage.
Laxative: Poorly absorbed magnesium ions create an osmotic gradient → draws water into the intestinal lumen → distends the bowel → stimulates peristalsis.
Rumen Alkalinizer: Directly neutralizes excess lactic acid produced during grain overload → increases rumen pH and alters rumen microflora activity.

安全性・警告

禁忌

Renal disease (due to risk of hypermagnesemia)
Gastric outlet obstruction (for aluminum-containing products)
Use cautiously in patients on sodium- or potassium-restricted diets (some products contain significant amounts)

有害事象

Diarrhea or frequent loose stools
Hypermagnesemia (especially in patients with severe renal insufficiency)
Constipation (if using combination products with aluminum)
Hypophosphatemia (with chronic use of aluminum-containing products)

注意事項

Magnesium-containing antacids are contraindicated in patients with renal disease. Oral magnesium hydroxide should only be used clinically in ruminants with documented rumen acidosis and should not be used for treatment of other suspected rumen disorders or hypomagnesemia. Chronic use may lead to electrolyte abnormalities.

医薬品相互作用

Quinidine

Increased absorption or pharmacologic effect may occur

Sodium Polystyrene Sulfonate

May decrease the potassium-lowering effectiveness; may cause metabolic alkalosis in renal failure patients

Sustained-release medications

May alter absorption by changing GI transit times when used at laxative dosages

Sympathomimetic agents

Increased absorption or pharmacologic effect may occur

Fluoroquinolones

Decreased absorption (chelation); separate doses by at least 2 hours

Tetracyclines

Decreased absorption (chelation); separate doses by at least 2 hours

Azole Antifungals (Ketoconazole, Itraconazole)

Decreased absorption due to increased gastric pH; separate doses by at least 2 hours

Digoxin