西替利嗪
**西替利嗪 (Cetirizine)** 是一種**第二代抗組織胺藥**，廣泛應用於人類醫學，並越來越多地應用於獸醫臨床，作為犬貓過敏及組織胺介導的搔癢症狀的輔助治療。 * **無嗜睡特性**：與第一代抗組織胺（如苯海拉明）不同，西替利嗪在標準劑量下難以穿透血腦屏障，因此較不易引起嗜睡。 * **活性代謝物**：它是哌嗪類衍生物，也是羥嗪 (Hydroxyzine) 的主要人類活性代謝物。 * **臨床應用**：主要用於犬貓的異位性皮膚炎、貓慢性鼻竇炎的輔助治療，偶爾用於馬的過敏症狀。雖然抗組織胺單獨使用於寵物嚴重過敏發作的效果不如人類顯著，但作為多模式、減少類固醇用量療法的一部分，仍具有臨床價值。
作用機制: Cetirizine acts as a highly selective, competitive antagonist at peripheral **H1 receptors**. * **Allergic cascade**: Allergen exposure → Mast cell/basophil degranulation → **Histamine** release → Binds to **H1 receptors** on sensory nerve endings and blood vessels → Pruritus, vasodilation, and edema. * Cetirizine competitively blocks this binding, preventing histamine-mediated effects. * It also appears to decrease histamine release from basophils in some species, though experimental studies in cats showed it does not reduce eosinophilic airway inflammation. * It lacks significant anticholinergic or anti-serotonergic activity, and tolerance to its antihistaminic effects is not thought to occur.
各物種劑量
- For adjunctive treatment of non-responsive chronic rhinosinusitis · 5 mg (total dose) PO q12h · PO · q12h
- General antihistamine use · 5 mg (total dose) per cat PO once daily · PO · q24h · No controlled studies evaluating effectiveness against other antihistamines.
- For adjunctive treatment of pruritus · 2.5-5 mg (total dose) per cat once daily · PO · q24h
- Antihistamine · 0.2-0.4 mg/kg PO q12h · PO · q12h · Based on pharmacokinetic and pharmacodynamic data, may be a useful antihistamine in horses.
- For atopic dermatitis · 1 mg/kg PO once daily with or without food · PO · q24h · Satisfactory control of pruritus in 18% of dogs evaluated in the study.
- For atopic dermatitis · 5-10 mg (total dose) PO once daily · PO · q24h
- For allergic dermatitis · 1 mg/kg PO q12h · PO · q12h
- For adjunctive treatment of pruritus · 0.5-1 mg/kg or 5-10 mg total dose once to twice daily · PO · q12-24h
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to cetirizine or hydroxyzine
- Combination products containing pseudoephedrine (e.g., Zyrtec-D) are strictly contraindicated in dogs and cats
不良反應
- Vomiting
- Hypersalivation (drooling)
- Somnolence (drowsiness/sedation, especially in small dogs at higher dosages)
- Dry mouth (reported in humans)
藥物相互作用
- CNS Depressants · Additive CNS depression if used concurrently with cetirizine · minor
監測
- Clinical efficacy (reduction in pruritus or allergic signs)
- Adverse effects (vomiting, hypersalivation, somnolence)
過量
Cetirizine generally has a wide margin of safety. * **Massive Overdose**: May cross the blood-brain barrier in overdose situations, leading to neurologic signs (hyperactivity or severe sedation). * **Cardiovascular Safety**: Unlike earlier non-sedating antihistamines (terfenadine and astemizole), cetirizine does not appreciably prolong the QT interval on ECG at high serum levels. * > **TOXICITY ALERT**: Overdoses of cetirizine products that also contain pseudoephedrine (e.g., Zyrtec-D 12 Hour) are highly dangerous and potentially fatal. Immediate veterinary intervention and consultation with an animal poison control center are required.
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。