左卡尼汀 / 左旋肉鹼
左卡尼汀（L-肉鹼）是一種天然存在的氨基酸衍生物，由蛋氨酸和賴氨酸在體內合成，對正常的脂肪利用和能量代謝至關重要。 在獸醫學中，它主要作為營養補充劑，用於輔助治療： * **犬擴張性心肌病 (DCM)**（特別是可卡犬和拳師犬，高達90%可能缺乏肉鹼）。 * **貓脂肪肝 (Feline Hepatic Lipidosis)**，促進肝臟脂質代謝和清除。 * 預防**阿黴素 (Doxorubicin) 引起的心臟毒性**。 * 輔助治療**丙戊酸 (Valproic acid) 中毒**。 **臨床要點：** 只有L-異構體（左卡尼汀）具有生物活性和益處。必須避免使用含有D-肉鹼的外消旋混合物，因為它們會競爭性抑制L-肉鹼的吸收並可能導致缺乏症。
作用機制: Levocarnitine acts as an essential cofactor for the **carnitine palmitoyltransferase (CPT)** system. It binds to long-chain free fatty acids in the cytosol, forming acylcarnitine, which is then transported across the inner mitochondrial membrane. Inside the mitochondria → the fatty acids undergo **beta-oxidation** → generating **ATP** (cellular energy). This mechanism is particularly crucial for the myocardium, which relies heavily on fatty acid oxidation for energy, and for the liver during states of lipid mobilization (e.g., feline hepatic lipidosis).
各物種劑量
- Adjunctive dietary therapy in cats with severe hepatic lipidosis · 250 mg PO once daily · PO · q24h · Use Carnitor; also supplement with taurine (250 mg once to twice daily), Vitamin E (10 Units/kg/day), water soluble vitamins and determine B12 status (treat while awaiting data at 1 mg/cat SC).
- Supplementation in cats with liver disease · 250-500 mg/day · PO · q24h
- Trial for treating canine dilated cardiomyopathy (large or giant breed dog) · 2 grams PO q8-12h · PO · q8-12h · Approximately 1 teaspoonful of pure powder
- Adjunctive therapy of dilated cardiomyopathy in American Cocker spaniels · 1 gram PO q8-12h · PO · q8-12h · Give with taurine. Approximately 1/2 teaspoonful.
- Severe myocardial failure in Boxers · 2-3 grams PO q12h · PO · q12h · 2-4 months · To determine if they respond
- Adjunctive treatment of American cocker spaniels with dilated cardiomyopathy · 1 g PO q12h · PO · q12h · Give with taurine 500 mg q12h PO
- Dilated cardiomyopathy in American Cocker spaniels · 1 g PO q8h · PO · q8h
- Dilated cardiomyopathy in Boxer dogs · 2 g PO q8h · PO · q8h
- Documented systemic carnitine deficiency · 50-100 mg/kg PO q8h · PO · q8h
- Myocardial carnitine deficiency only · 200 mg/kg PO q8h · PO · q8h
給藥途徑
禁忌症
- Use of D-carnitine or racemic (D,L) mixtures (competitively inhibits L-carnitine uptake)
不良反應
- Gastrointestinal upset (loose stools, diarrhea, nausea, vomiting) - usually mild and dose-dependent
- Increased body odor (reported in human patients)
藥物相互作用
- Valproic acid · Patients receiving valproic acid may require higher dosages of levocarnitine due to drug-induced carnitine depletion.
監測
- Clinical efficacy (improvement in cardiac or hepatic signs)
- Periodic blood chemistries (recommended in humans, value in veterinary medicine is undetermined)
過量
Levocarnitine is a relatively safe drug. * **Minor overdoses**: Need only to be monitored. * **Massive overdoses**: Consider gut emptying (emesis or gastric lavage). Refer to a veterinary poison control center for more information.
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。