S-アデノシルメチオニン (SAMe)
**S-アデノシルメチオニン (SAMe)** は、体内に自然に存在する内因性分子であり、主に**肝保護薬**として獣医療で広く利用されている栄養補助食品です。 主な臨床応用： * **肝疾患**：慢性肝炎、肝リピドーシス、胆管肝炎、猫の三臓器炎などの補助治療として使用されます。 * **中毒の管理**：枯渇したグルタチオンを補充することにより、**アセトアミノフェン**や**キシリトール**中毒などの急性肝毒性物質による肝障害の治療において重要な役割を果たします。 * **その他の用途**：変形性関節症、加齢に伴う認知機能障害（犬の認知機能障害症候群）、および肝毒性の可能性がある薬剤（フェノバルビタールなど）を長期投与されている患者にも有益な場合があります。 > **臨床のポイント**：純粋なSAMeは非常に反応性が高く不安定であるため、市販の製剤は安定性を向上させるために様々な塩（トシル酸塩など）を使用しています。製品間で生物学的利用能に大きな差があるため、信頼性の高い獣医療専用ブランドを選択することが強く推奨されます。
作用機序: SAMe is synthesized from the amino acid methionine and ATP via the enzyme **SAMe synthetase**. In liver compromise, this enzyme's activity is a rate-limiting step, leading to systemic SAMe deficiency. Exogenous SAMe bypasses this block and participates in three major biochemical pathways: * **Transsulfuration** → Generates sulfur-containing compounds → Precursor to **Glutathione (GSH)**. Glutathione is the liver's master antioxidant, essential for ROS scavenging and cellular detoxification. Exogenous SAMe prevents GSH depletion. * **Transmethylation** → Serves as a methyl donor → Essential for phospholipid synthesis (e.g., phosphatidylcholine) → Maintains cell membrane structure, fluidity, and function. * **Aminopropylation** → Donates aminopropyl groups → Source of polyamines → Promotes anti-inflammatory effects, protein/DNA synthesis, and **hepatocyte replication/regeneration**. Additionally, SAMe inhibits hepatocyte apoptosis secondary to alcohol or bile acid accumulation.
動物種別の用量
- General dosing / Liver support · 18 mg/kg (or based on weight: <5.5 kg: 90 mg; 5.5-11 kg: 180-225 mg) · PO · q24h · Give on an empty stomach, at least one hour before feeding.
- Liver Disease (necro-inflammatory/cholestatic, feline hepatic lipidosis) · 20 mg/kg · PO · q24h · Give on an empty stomach; use a proven bioavailable product.
- Liver disease, cognitive dysfunction, improve bile flow · 100 mg/cat or 20 mg/kg · PO · q24h · Long-term as needed · Administer on an empty stomach at least 1 hour before food. Tablets should be given whole.
- General dosing / Liver support · 18 mg/kg (or based on weight: <5.5 kg: 90 mg; 5.5-11 kg: 180-225 mg; 11-16 kg: 225 mg; 16-29.5 kg: 450 mg; 29.5-41 kg: 675 mg; >41 kg: 900 mg) · PO · q24h (may divide q12h if giving >1 tablet) · Give on an empty stomach, at least one hour before feeding.
- Liver Disease (necro-inflammatory/cholestatic, vacuolar hepatopathy) · 20 mg/kg · PO · q24h · Give on an empty stomach; use a proven bioavailable product.
- Liver disease, cognitive dysfunction, adjunctive therapy · At least 100 mg for every 10 kg or 20 mg/kg · PO · q24h · Long-term as needed · Administer on an empty stomach at least 1 hour before food. Tablets should be given whole.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- No absolute contraindications
- Use with caution in pregnant animals (safety not definitively proven)
- No absolute contraindications documented
- Use with caution during pregnancy (safety not established)
有害事象
- Immediate post-dose vomiting
- Anorexia
- Anxiety
- Nausea (reported in humans)
- Diarrhea (reported in humans)
- Flatulence (reported in humans)
- Nausea
- Vomiting
- Diarrhoea
- Paradoxical anxiety
- Dry mouth (reported in humans)
- Headache (reported in humans)
- Sweating (reported in humans)
- Dizziness (reported in humans)
薬物相互作用
- Tramadol · Theoretical risk of additive serotonergic effects (serotonin syndrome) · major
- Meperidine · Theoretical risk of additive serotonergic effects · major
- Dextromethorphan · Theoretical risk of additive serotonergic effects
- Pentazocine · Theoretical risk of additive serotonergic effects · major
- Monoamine oxidase inhibitors (MAOIs) (e.g., selegiline) · Theoretical risk of additive serotonergic effects
- Selective serotonin reuptake inhibitors (SSRIs) (e.g., fluoxetine) · Theoretical risk of additive serotonergic effects
- Tricyclic antidepressants (TCAs) (e.g., amitriptyline, clomipramine) · Theoretical risk of additive serotonergic effects
- Selegiline · Additive serotonergic effects; potential for serotonin syndrome · major
- Fluoxetine · Additive serotonergic effects; potential for serotonin syndrome · major
- Clomipramine · Additive serotonergic effects; potential for serotonin syndrome · major
- Amitriptyline · Additive serotonergic effects; potential for serotonin syndrome · major
- Paracetamol · SAMe may increase the clearance of drugs undergoing hepatic glucuronidation · moderate
モニタリング
- Clinical signs (appetite, activity, attitude)
- Liver enzymes (ALT, AST, ALP, GGT)
- Bilirubin
- Bile acids
- Liver biopsies (if indicated)
- Hepatic and erythrocyte glutathione levels (Note: may require 1-4 months before changes in lab values are noted)
- Liver enzyme panel (ALT, AST, ALP, GGT)
- Total bilirubin and bile acids
- Clinical signs of cognitive improvement or behavioral changes
- Signs of serotonin syndrome (agitation, tremors, hyperthermia) if used concurrently with serotonergic drugs
過量投与
SAMe appears to be quite safe. The LD50 in rodents exceeds 4.65 grams/kg. Toxicity studies in dogs and cats at usual prescribed dosages demonstrated no deleterious effects. In the event of a massive overdose, mild gastrointestinal effects (nausea, vomiting, diarrhea) may be observed, but it is highly unlikely to require specific medical treatment beyond supportive care.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。