甲巰咪唑
Methimazole
1-methyl-1,3-dihydro-2H-imidazole-2-thione (Thiamazole)
別名: Tapazole · Felimazole · Northyx · Antitiroide · Danantizol · Favistan · Mercaptizol · Metibasol · Strumazol · Thacapzol · Thycapzol · Thyrozol · Tirodril · Unimazole · Thiafeline · Thyronorm · Thiamazole · Mercazolylum · Methylmercaptoimidazole · Thiamazolum · Tiamazol · Methimazole · Mercazolil
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
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| As an investigative method to reduce nephrotoxicity associated with cisplatin therapy | 40 mg/kg IV over one minute prior to cisplatin. | IV | once | Prior to cisplatin | 🌎 NA |
| Hyperthyroidism | 2.5-5 mg/dog | PO | q12h | Long-term | 🌍 EU |
- As an investigative method to reduce nephrotoxicity associated with cisplatin therapy: No commercially available parenteral product in USA at time of writing.
- Hyperthyroidism: Dose depends on size.
貓
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Hyperthyroidism | The starting dose is 2.5 mg administered every 12 hours. Following 3 weeks of treatment, the dose should be titrated to effect based on individual serum total T4 (TT4) levels and clinical response. Dose adjustments should be made in 2.5 mg increments. The maximum total dosage is 20 mg per day divided, not to exceed 10 mg as a single administration. | PO | q12h | Lifelong | 🌎 NA |
| Hyperthyroidism (cats with azotemia or for clients declining radioiodine) | 1.25-5 mg per cat twice daily (start at lower end. | PO | q12h | Lifelong | 🌎 NA |
| Hyperthyroidism (transdermal administration) | 2.5 mg to inner pinna q12h. | topical | q12h | Lifelong | 🌎 NA |
| Hyperthyroidism (gradual titration) | Initially, 2.5 mg (total dose) PO once a day for 2 weeks. If adverse reactions not noted... increase to 2.5 mg PO twice daily and the same parameters are checked in another 2 weeks. The dosage should then be increased every 2 weeks by 2.5 mg per day until serum T4 is between 13 and 26 nmol/L or adverse effects develop. | PO | q24h initially, then q12h | Lifelong | 🌎 NA |
| Hyperthyroidism (based on renal status) | If no signs of renal insufficiency/failure, begin at 5 mg (total dose) PO twice daily in cases with severely increased T4 levels. If renal insufficiency present (or not sure), start at 2.5 mg twice daily. If azotemia and overt renal failure, start at 1.25 mg twice a day. | PO | q12h | Lifelong | 🌎 NA |
| Hyperthyroidism | 2.5 mg/cat | PO | q12h | Long-term | 🌍 EU |
| Hyperthyroidism | Apply transdermal gel to pinna | Topical | q12h | Long-term | 🌍 EU |
- Hyperthyroidism (transdermal administration): Methimazole (50 mg/mL; 5 mg/0.1 mL) in PLO. Person applying should wear gloves or finger cots. Somewhat lower efficacy than PO (67% vs 82% euthyroid at 4 weeks). Lower incidence of GI effects.
- Hyperthyroidism (based on renal status): Monitor in 1-2 weeks (T4, CBC with platelet count, renal blood parameters, urinalysis).
- Hyperthyroidism: 2 to 3 weeks of treatment generally needed to establish euthyroidism. Adjust dose based on T4 monitoring.
- Hyperthyroidism: Used particularly in fractious cats or those with GI side effects. Wear gloves.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
概覽
甲巰咪唑 (Methimazole) 是一種硫咪唑衍生物抗甲狀腺藥物，在北美被視為貓甲狀腺機能亢進症的黃金標準內科療法。
主要臨床重點：
- 主要用途：控制貓的甲狀腺機能亢進。它能有效降低循環中的甲狀腺激素濃度，改善體重減輕、多食和心搏過速等臨床症狀。
- 替代給藥途徑：對於難以餵食口服藥的貓，可將甲巰咪唑配製成經皮吸收凝膠 (PLO gel) 塗抹於耳廓內側，具有良好的臨床療效（雖然略低於口服），且可能減少胃腸道副作用。
- 研究性用途：在狗中，曾被用作靜脈注射以預防順鉑 (cisplatin) 引起的腎毒性。
- 臨床要點：甲巰咪唑僅能控制而無法治癒甲狀腺機能亢進。除非進行根治性治療（放射性碘或甲狀腺切除術），否則需要終身每日服藥。
作用機轉
Methimazole acts directly within the thyroid gland to block the synthesis of thyroid hormones (T3 and T4).
- Mechanism: It actively inhibits the enzyme thyroid peroxidase (TPO).
- Pathway: Inhibition of TPO → prevents the oxidation of iodide to iodine → blocks the incorporation of iodine into tyrosyl residues of thyroglobulin → inhibits the coupling of iodinated tyrosyl residues to form iodothyronine (T3 and T4).
- Important Note: Methimazole has no effect on the release or activity of thyroid hormones that are already formed and stored, or those currently in systemic circulation. This accounts for the 1 to 3 week lag time often seen before serum T4 levels significantly decrease and clinical improvement is noted.
安全性與警告
禁忌症
- Hypersensitivity to methimazole, carbimazole, or polyethylene glycol
- Autoimmune disease
- Primary liver disease
- Renal failure
- Hematologic disorders or coagulopathies
- Pregnant or lactating queens
- Pregnant queens
- Animals with known hypersensitivity to thiamazole or carbimazole
不良反應
- Vomiting
- Depression/Lethargy
- Transient eosinophilia, leukopenia, and lymphocytosis
- Self-induced facial excoriations (pruritus)
- Bleeding/Coagulopathies
- Agranulocytosis
- Positive direct antiglobulin test (DAT)
- Positive ANA (in chronic use >6 months)
- Acquired myasthenia gravis (rare)
- Inappetence / Anorexia
- Jaundice / Hepatopathy
- Cytopenias (thrombocytopenia, leukopenia, anemia)
- Immune-mediated diseases (e.g., myasthenia gravis)
- Dermatological changes (pruritus, facial excoriation, alopecia)
- Decreased GFR (unmasking of renal failure)
注意事項
Black Box / Handling Warning: Pregnant women, women who may become pregnant, and nursing mothers should wear gloves when handling tablets, litter, or bodily fluids of treated cats.
- Renal Unmasking: Restoring euthyroidism can decrease glomerular filtration rate (GFR) and unmask underlying chronic kidney disease in cats. Careful monitoring of renal values is essential.
- Hematologic & Hepatic Monitoring: Severe adverse effects like agranulocytosis and hepatotoxicity usually occur within the first 3 months. Routine bloodwork monitoring is critical during this phase.
- Nursing: Kittens should be placed on a milk replacer if the mother is receiving the drug, as it is excreted in milk and can cause fetal/neonatal hypothyroidism.
藥物交互作用
Methimazole can reduce hepatic oxidation of benzimidazoles and increase blood levels.
A reduction in dose may be needed when the patient becomes euthyroid.
Potential for increased risk for hepatotoxicity; increased monitoring (LFT's) necessary.
Methimazole may decrease digoxin efficacy, but a reduction in dose may be needed when the patient becomes euthyroid.
Concurrent use of phenobarbital may reduce the clinical effectiveness of methimazole.
A reduction in dose may be needed when the patient becomes euthyroid.
Anticoagulants may be potentiated by methimazole. Increased monitoring of anticoagulant effect is warranted.
Reduce hepatic oxidation and may lead to increased circulating thiamazole concentrations
Thiamazole interferes with radioiodine uptake; must be discontinued prior to I-131 treatment
Concurrent use is not recommended as it confounds dietary management and iodine restriction
監測
- Baseline and every 2-3 weeks for the first 3 months: CBC, platelet count, Serum T4
- Liver function tests and ANA if indicated by symptomatology
- After stabilization (at least 3 months): T4 at 3-6 month intervals
- Renal parameters (BUN, Creatinine, USG) to monitor for unmasked kidney disease
- Cats receiving >10 mg/day require more frequent monitoring
- Serum total T4 (measure 4-6 hours post-pill)
- Haematology (CBC for cytopenias)
- Biochemistry (BUN, Creatinine, Liver enzymes)
- Monitor at 3, 6, 10, and 20 weeks after starting therapy, and every 3 months thereafter
藥物動力學
半衰期
吸收
In normal cats, oral bioavailability is highly variable (45-98%). There is usually a 1-3 week lag time between starting the drug and significant reductions in serum T4.
分佈
Volume of distribution in cats is 0.12-0.84 L/kg. Methimazole actively concentrates in thyroid tissue. High levels cross the placenta and are detected in breast milk.
代謝
Undergoes hepatic metabolism.
排除
Eliminated primarily via the kidneys and feces after hepatic metabolism.
過量
Acute toxicity from overdosage mirrors severe adverse effects: agranulocytosis, hepatopathy, and thrombocytopenia are the most serious concerns.
Treatment:
- Follow standard protocols for oral ingestion (empty stomach if not contraindicated, administer activated charcoal).
- Provide symptomatic and supportive care (e.g., IV fluids, hepatoprotectants, broad-spectrum antibiotics if neutropenic).
可用產品
劑型
- Oral tablets (sugar-coated, plain, scored)
- Transdermal gel (compounded)
- Intravenous injection (investigational/compounded)
- Oral: 1.25 mg tablet
- Oral: 2.5 mg tablet
- Oral: 5 mg tablet
- Oral: 5 mg/ml solution
- Transdermal gel (named patient basis/compounded)
獸醫用
- Methimazole Tablets (sugar-coated): 2.5 mg & 5 mg (Felimazole - Dechra)
- Felimazole 1.25 mg, 2.5 mg, 5 mg tablets
- Thiafeline 2.5 mg, 5 mg tablets
- Thyronorm 5 mg/ml oral solution
人用標示
- Methimazole Tablets (plain & scored): 5 mg, 10 mg, 15 mg & 20 mg (Tapazole, Northyx, generic)
各地核准狀態
POM-V classification.
POM-V classification.
暫無法規資料: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store tablets in well-closed, light-resistant containers at room temperature; protect from moisture. Compounded transdermal PLO gels typically have a guaranteed stability of 2 weeks.
飼主須知
了解您寵物的藥物
甲巰咪唑 (Methimazole) 是一種用於控制貓咪甲狀腺機能亢進（甲狀腺過度活躍）的日常藥物。
- 作用原理：它能阻斷過多甲狀腺激素的產生，幫助您的貓咪恢復正常的體重、心率和行為。
- 非治癒性：此藥物能控制疾病，但無法治癒。您的貓咪可能需要終身服用此藥。
- 需要耐心：通常需要 1 到 3 週的時間才能看到貓咪症狀有明顯改善。
餵藥技巧
- 藥丸有非常苦的味道。除非獸醫師指示，否則請勿將其壓碎，因為貓咪可能會拒絕食用混有藥粉的食物。
- 如果您在餵食藥丸時遇到困難，請向您的獸醫師詢問經皮吸收凝膠，這是一種可以塗抹在貓咪耳朵無毛處的替代劑型。
安全警告
人類安全：甲巰咪唑會影響人類的甲狀腺功能和胎兒發育。孕婦、準備懷孕的女性及哺乳期婦女在接觸藥丸、貓砂或治療貓咪的體液時，應戴上手套。
注意事項
如果您的貓咪出現以下情況，請立即聯繫您的獸醫師：
- 嘔吐或食慾不振（尤其是在最初幾週內）
- 極度嗜睡或虛弱
- 劇烈抓撓臉部或頸部
- 不明原因的瘀傷或出血
VetSheet 藥物參考供合格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商最新仿單。