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左旋甲狀腺素

Levothyroxine

L-3,5,3',5'-tetraiodothyronine

甲狀腺荷爾蒙補充劑PO狗貓

別名: Leventa · Soloxine · Thyforon · l-Thyroxine · T4 · Levothyroxine sodium

由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本

0.02-0.04 mg/kg/day OR 0.5 mg/m2 body surface area dailyPO· sid or divided bid· Lifelong

這是按體表面積（mg/m²）計算的劑量；給藥前須先把體重換算為體表面積。

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。

各物種劑量

🌎 NA — North America🌍 EU — Europe

狗

適應症劑量途徑頻次療程地區
Hypothyroidism0.02-0.04 mg/kg/day OR 0.5 mg/m2 body surface area dailyPOsid or divided bidLifelong🌍 EU
  • Hypothyroidism: Dose given with food. Monitor serum T4 levels pre-dosing and 4-8 hours after dosing.

貓

適應症劑量途徑頻次療程地區
Hypothyroidism0.02-0.04 mg/kg/day OR 0.5 mg/m2 body surface area dailyPOsid or divided bidLifelong🌍 EU
  • Hypothyroidism: Dose given with food. Monitor serum T4 levels pre-dosing and 4-8 hours after dosing.

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。

正在為病患診症？VetSheet 的 AI 會把藥物、劑量與療程直接寫入結構化診症筆記。了解 VetSheet 如何運作

概覽

左旋甲狀腺素（l-Thyroxine 或 T4）是一種合成的天然甲狀腺荷爾蒙。它是獸醫學中治療​甲狀腺機能低下症​的首選藥物。

​臨床警告：​ 患有潛在心臟疾病的病患在初期需要較低的劑量，以防止過度的心臟刺激。在患有自體免疫多發性內分泌腺綜合症的病患中，它也可能誘發愛迪生氏症（腎上腺皮質機能低下症）。

作用機制

Levothyroxine acts as a replacement for endogenous thyroxine. It enters cells and is converted to the more active T3 (triiodothyronine). T3 then binds to specific intracellular thyroid hormone receptors in the nucleus → alters gene expression → regulates metabolism, growth, and development.

安全性與警告

禁忌症

  • Uncorrected adrenal insufficiency (Addison's disease)
  • Acute myocardial infarction (general precaution)

不良反應

  • Tachycardia
  • Excitability
  • Nervousness
  • Excessive panting
  • Unmasking of Addison's disease

注意事項

Use with caution in patients with pre-existing cardiac disorders; lower initial doses are required. Monitor diabetic patients carefully during the initiation of therapy as insulin requirements may change. Many drugs may affect thyroid function tests, which can complicate therapeutic monitoring.

藥物相互作用

CatecholaminesModerate

Actions of catecholamines are enhanced by thyroxine

SympathomimeticsModerate

Actions of sympathomimetics are enhanced by thyroxine

InsulinModerate

Altered insulin requirements; monitor carefully during initiation of therapy

OestrogensModerate

May increase thyroid requirements by increasing thyroxine-binding globulin

CiclosporinModerate

Therapeutic effect may be reduced by thyroid hormones

DigoxinModerate

Therapeutic effect may be reduced by thyroid hormones

DigitoxinModerate

Therapeutic effect may be reduced by thyroid hormones

KetamineMajor

Tachycardia and hypertension may develop when given to patients receiving thyroid hormones

監測

  • Serum total T4 levels (pre-pill trough and 4-8 hours post-pill peak)
  • Clinical response (resolution of lethargy, weight gain, dermatological signs)
  • Signs of thyrotoxicosis (panting, tachycardia, hyperactivity)
  • Blood glucose in diabetic patients

藥物動力學

半衰期

貓10-16 hours狗10-16 hours

吸收

Variable oral absorption in dogs (typically 10-50%). Bioavailability is significantly influenced by food; therefore, consistent administration with or without food is recommended.

分佈

Highly protein bound (>99%) to thyroxine-binding globulin, transthyretin, and albumin.

代謝

Deiodinated in the liver and peripheral tissues to the active form T3 and inactive reverse T3. Also undergoes hepatic conjugation.

排除

Excreted primarily in feces via biliary excretion, with a smaller amount excreted in urine.

過量

Clinical signs of overdosage (thyrotoxicosis) include tachycardia, excitability, nervousness, and excessive panting. Treatment involves withholding the medication until signs resolve, then restarting at a lower dose. Acute massive overdose may require gastrointestinal decontamination and supportive care (e.g., beta-blockers for severe tachycardia).

可用產品

劑型

  • 0.1 mg tablet
  • 0.2 mg tablet
  • 0.3 mg tablet
  • 0.5 mg tablet
  • 0.8 mg tablet
  • 1 mg/ml oral solution

獸醫用

  • Leventa 1 mg/ml oral solution
  • Soloxine tablets (various strengths)
  • Thyforon tablets (various strengths)

人用標示

  • Levothyroxine sodium tablets (various strengths, e.g., 25 mcg, 50 mcg, 100 mcg)

各地核准狀態

United States✓ 已核准處方藥FDA/CVM
🐕 Dogs

Approved as Thyro-Tabs Canine and others.

European Union✓ 已核准處方藥EMA
🐕 Dogs🐈 Cats

POM-V classification.

United Kingdom✓ 已核准處方藥VMD
🐕 Dogs🐈 Cats

POM-V classification.

暫無法規資料: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

儲存與穩定性

Store at room temperature in tightly closed containers. Protect from light and moisture.

飼主須知

請固定時間餵食此藥物，並保持一致的給藥方式（固定與食物一起或空腹）。未經獸醫師同意，​請勿隨意更換廠牌​，因為不同廠牌的吸收率可能不同。觀察是否有藥物過量的症狀，如過度喘氣、焦躁不安、多飲或多尿。此藥物通常需要終身服用，並需要定期進行血液檢查以確保劑量正確。

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。