S-腺苷甲硫氨酸 (SAMe)
**S-腺苷甲硫氨酸 (SAMe)** 是一種天然存在的內源性分子，也是獸醫學中廣泛使用的營養補充品，主要作為**肝臟保護劑**。 主要臨床應用包括： * **肝臟疾病**：作為慢性肝炎、肝脂質沉積症、膽管肝炎及貓三體炎的輔助治療。 * **毒性管理**：透過補充耗竭的穀胱甘肽，在治療急性肝毒素（如**普拿疼/對乙醯氨基酚**或**木糖醇**中毒）引起的肝損傷中扮演關鍵角色。 * **其他用途**：可能對骨關節炎、與年齡相關的認知功能障礙（犬認知功能障礙症候群），以及長期服用具肝毒性潛力藥物（如苯巴比妥、洛莫司汀）的病患有益。 > **臨床提示**：由於純 SAMe 具高反應性且不穩定，市售配方多使用各種鹽類（如甲苯磺酸鹽）以提高穩定性。不同產品間的生物利用度差異極大，強烈建議選擇信譽良好、專為獸醫設計的品牌。
作用機制: 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.
各物種劑量
- 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.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- 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)
不良反應
- 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)
藥物相互作用
- 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
監測
- 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
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 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。