硫胺素 (維生素B1)
硫胺素（維生素B1）是一種水溶性維生素，對碳水化合物代謝和正常神經功能至關重要。 **主要臨床重點：** * **缺乏原因：** 在小動物中，缺乏通常是由於飲食攝入不足（例如未補充營養的全肉飲食、高溫破壞的商業飲食）或攝入含有硫胺素酶的食物（如生魚）所致。在反芻動物中，通常繼發於產生硫胺素酶的瘤胃細菌或攝入含有硫胺素酶的植物（如蕨類），導致**腦軟化症 (PEM)**。 * **臨床症狀：** 表現為胃腸道問題（厭食、流涎）、嚴重的神經肌肉/中樞神經系統症狀（共濟失調、癲癇發作、貓頸部腹側屈曲、反射喪失）或心律不整。 * **輔助用途：** 常用於**乙二醇中毒**（將代謝途徑轉移以避免產生毒性草酸鹽）和**鉛中毒**的輔助治療。 * **臨床提示：** 由於大腦高度依賴碳水化合物代謝，中樞神經系統對硫胺素缺乏極為敏感，因此在出現神經症狀時迅速補充至關重要。
作用機制: Thiamine is actively transported into cells where it combines with adenosine triphosphate (ATP) to form **thiamine diphosphate (thiamine pyrophosphate or TPP)**. * **Enzymatic Co-factor:** TPP is an essential coenzyme for several key metabolic enzymes, including **pyruvate dehydrogenase**, **alpha-ketoglutarate dehydrogenase** (both critical for the Krebs cycle/aerobic energy production), and **transketolase** (pentose phosphate pathway). * **Metabolic Pathway:** Glucose → Pyruvate. Without TPP, pyruvate cannot be converted into acetyl-CoA. * **Pathophysiology of Deficiency:** Diminished NADH production forces the cell into anaerobic glycolysis, converting accumulated pyruvic acid into lactic acid → **Lactic acidosis** and cellular energy failure (especially in high-demand tissues like the brain and heart).
各物種劑量
- Polioencephalomalacia · Initially, 10 mg/kg IV; then, 10 mg/kg IM twice daily · IV, IM · twice daily · 2-3 days · If no improvement within 4 days, may be advisable to recommend slaughter.
- Thiamine deficiency · 20-200 mg · IM, SC, or IV · Not specified · Depending on formulation
- Polioencephalomalacia · Initially, 10 mg/kg IV; then, 10 mg/kg IM twice daily · IV, IM · twice daily · 2-3 days · If no improvement within 4 days, may be advisable to recommend slaughter.
- Thiamine deficiency · 100-250 mg · parenterally · twice a day · Experimentally, as little as 1 mg is effective
- Thiamine deficiency · 10-20 mg/kg · IM · Not specified · for several days
- Adjunctive treatment of hepatic lipidosis · 100 mg of thiamine in one liter of crystalloid fluids · IV · Not specified · With additional soluble B vitamins. Indicated if neck ventroflexion is present.
- Thiamine deficiency · 100-250 mg · SC · twice daily · for several days until regression of symptoms with complete recovery
- Thiamine deficiency · 10-20 mg/kg IM or SC two to three times daily until signs abate, then 10 mg/kg PO once daily · IM, SC, PO · two to three times daily, then once daily · 21 days for PO phase
給藥途徑
禁忌症
- Known hypersensitivity to thiamine or any of its components
- Known hypersensitivity to thiamine
不良反應
- Hypersensitivity or anaphylactic reactions (rare)
- Vasovagal anaphylactic response in cats (cardiac arrest, severe bradycardia, apnea, hypotension, collapse) when given SC (rare)
- Injection site tenderness or muscle soreness (IM)
- Pain at the injection site (IM/SC)
- Anaphylaxis or hypersensitivity reactions (primarily with rapid IV administration)
藥物相互作用
- Neuromuscular blocking agents · Thiamine may enhance the activity of neuromuscular blocking agents; clinical significance is unknown. · minor
監測
- Clinical efficacy (resolution of neurologic, gastrointestinal, or cardiac signs)
- Electrolyte levels (potassium, phosphate, magnesium) if treating conditions like feline hepatic lipidosis
- Resolution of clinical signs of thiamine deficiency (e.g., neurological improvement)
- Dietary intake and nutritional balance
過量
Very large doses of thiamine in laboratory animals have been associated with **neuromuscular or ganglionic blockade**, though the clinical significance in veterinary patients is unknown. * **Massive Doses:** May cause hypotension and respiratory depression. * **Lethal Dose:** A lethal dose of 350 mg/kg has been reported. * **Treatment:** Generally, no specific treatment is required for most overdoses due to its water-soluble nature and rapid renal excretion.
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