ラクツロース
Lactulose
4-O-β-D-galactopyranosyl-D-fructose
別名: Cephulac · Constulose · Enulose · Kristalose · Generiac · Duphalac · Lactugal · Laevolac · Lactulosum
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
監査済み v13 用量エビデンス
構造化された用量計算エビデンスConstipation (extra-label)
選択肢 1
認証済み獣医師の確認が必要
- q6-8h
選択肢 2
認証済み獣医師の確認が必要
- q8-12h
NA
必ず考慮する臨床コンテキスト (2)
- NOTE: If using the crystals for oral solution: One gram of the crystals is equivalent to 1.5 mL of the liquid.
- Lactulose syrup should be stored protected from light in tight containers, preferably at room temperature (20°C-25°C [68°F-77°F]); avoid freezing. Darkening of the solution may occur, but this does not affect drug potency. Exposure to heat or light may cause extreme darkening or cloudiness; these solutions should be discarded. Lactulose solutions may precipitate; crystals dissolve with gentle reheating.
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。
概要
ラクツロースは、ガラクトースとフルクトースからなる合成二糖類です。獣医療においては、主に以下の2つの重要な役割を果たします：
- 肝性脳症（HE）の管理：肝機能障害（門脈体循環シャント、重度の肝硬変など）の患者において、血中アンモニア濃度を低下させるための基本治療薬です。結腸内でアンモニアを捕捉し、血流への神経毒の蓄積を防ぎます。
- 浸透圧性下剤：慢性便秘や宿便、特に巨大結腸症を患う猫の管理に広く使用されます。
臨床のポイント：猫はラクツロースの粘り気のある甘いシロップを嫌がる傾向があり（流涎や抵抗の原因となります）、結晶製剤（Kristalose）をウェットフードに混ぜて与える方が受け入れられやすく、長期的なコンプライアンスが向上することが多いです。
作用機序
Lactulose exerts its effects locally in the gastrointestinal tract through two distinct mechanisms:
- Ammonia Reduction (Ion Trapping): Lactulose is not hydrolyzed by mammalian gut enzymes. It reaches the colon intact, where it is fermented by resident bacteria into low-molecular-weight organic acids (lactic, formic, and acetic acids). This fermentation drops the colonic pH. The acidic environment causes diffusible, neurotoxic ammonia (NH3) to migrate from the bloodstream into the colon, where it is protonated into the non-diffusible ammonium ion (NH4+). The ammonium is then trapped in the lumen and excreted in the feces.
- Osmotic Laxative Effect: The unabsorbed disaccharide and its organic acid metabolites exert a strong osmotic pressure, drawing water into the bowel lumen. This increases fecal bulk and moisture, stimulating colonic peristalsis and facilitating bowel movements.
安全性・警告
禁忌
- Patients requiring a low-galactose diet
- Use with caution in diabetic patients (contains free lactose and galactose)
- Use with caution in patients with preexisting fluid and electrolyte imbalances
- Severely encephalopathic animals at risk of inhalation/aspiration
- Gastrointestinal obstruction
- Animals at risk of gastrointestinal perforation
有害事象
- Flatulence
- Gastric distention
- Abdominal cramping
- Diarrhea (dose-dependent)
- Dehydration (secondary to excessive diarrhea)
- Hypersalivation/aversion in cats (due to taste/texture)
- Diarrhoea
- Dehydration (with excessive dosing)
注意事項
Diabetic Patients: Lactulose syrup contains some free lactose and galactose, which may alter insulin requirements. Electrolyte Imbalances: Lactulose-induced diarrhea can exacerbate preexisting fluid and electrolyte imbalances. Monitor hydration and serum electrolytes during long-term therapy. Feline Administration: The syrup is notoriously difficult to administer to cats due to taste aversion; consider using lactulose crystals mixed with food.
医薬品相互作用
Non-adsorbable antacids may reduce the colonic acidification effects and overall efficacy of lactulose.
Should not be used concurrently; loose stools may be falsely attributed to lactulose, resulting in inadequate dosing for hepatic encephalopathy.
Theoretically, oral antibiotics could eliminate the colonic bacteria required to metabolize lactulose, reducing its efficacy. However, clinical synergy is often observed when treating hepatic encephalopathy. Enhanced monitoring is recommended.
Synergy may occur when used together for hepatic encephalopathy.
Lactulose syrup contains free lactose and galactose, which may alter insulin requirements in diabetic patients.
Can be inactivated because lactulose decreases the pH of the colon.
監視
- Clinical efficacy: Aim for 2-3 soft, semi-formed stools per day when used for hepatic encephalopathy or constipation.
- Serum electrolytes (especially during long-term use or in patients with preexisting fluid/electrolyte abnormalities).
- Faecal consistency (aim for 2-3 soft, formed stools per day)
- Blood ammonia levels (in hepatic encephalopathy)
- Hydration status and electrolytes
- Blood glucose levels (in diabetic patients)
薬物動態
吸収
In humans, less than 3% of an oral dose of lactulose is absorbed in the small intestine.
分布
Acts locally within the gastrointestinal tract; systemic distribution is minimal.
代謝
The absorbed fraction is not metabolized. The unabsorbed fraction reaching the colon is metabolized by resident bacteria into low molecular weight acids (lactic, formic, acetic) and CO2.
消失
The small absorbed fraction is excreted unchanged in the urine within 24 hours. The unabsorbed, metabolized fraction is excreted in the feces.
過剰投与
Excessive doses of lactulose may cause flatulence, severe diarrhea, abdominal cramping, and dehydration.
Management:
- Reduce the dosage or temporarily discontinue the medication.
- Provide supportive care, including replacement of fluids and electrolytes if dehydration or imbalances occur.
製品
製剤
- Oral solution (syrup): 10 g/15 mL
- Crystals for oral solution: 10 g and 20 g packets
- Oral syrup: 3.1-3.7 g/5 ml
- Oral syrup: 10 g/15 ml
ヒト用医薬品
- Lactulose Solution: 10 grams lactulose per 15 mL (Cephulac, Constulose, Enulose, Generiac)
- Lactulose Crystals for Oral Solution: 10 grams and 20 grams packets (Kristalose)
- Duphalac (syrup)
- Lactugal (syrup)
- Laevolac (syrup)
規制ステータス
Widely used in veterinary medicine.
Classified as 'P' (Pharmacy medicine) in the UK for human formulations often used off-label in animals.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store lactulose syrup in tight containers, preferably at room temperature; avoid freezing. If exposed to heat or light, darkening or cloudiness of the solution may occur, but this does not affect drug potency.
飼主向け情報
期待される効果
- 治療の目標：ラクツロース治療の理想的な結果は、1日に2〜3回の柔らかく形のある便（ソフトクリームのような固さ）が出ることです。
- 用量の調整：獣医師は、ペットの便の固さに応じて用量を微調整するよう指示することがあります。
重要な警告
- 下痢に注意：ペットが水様性の下痢をした場合は、危険な脱水症状を引き起こす可能性があるため、すぐに投薬を中止し、獣医師に連絡してください。
- 肝疾患の場合：肝疾患（肝性脳症）のためにこの薬を服用しており、神経症状（ふらつき、一点を見つめる、頭を壁に押し付けるなど）が悪化した場合、または1日の軟便の回数が2回未満の場合は、すぐに獣医師に連絡してください。
猫への投薬のヒント
- 猫はシロップの粘り気のある甘い味を嫌がることが多く、よだれを大量に垂らしたり逃げたりすることがあります。
- 液体の投薬が難しい場合は、ラクツロース結晶（Kristalose）について獣医師に相談してください。缶詰のフードに簡単に混ぜることができ、猫も受け入れやすいことが多いです。
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。