羥嗪 (Hydroxyzine)
羥嗪是一種第一代抗組織胺藥物，廣泛應用於獸醫學中。主要用於其止癢和抗組織胺特性，是治療犬貓異位性皮膚炎、跳蚤過敏性皮膚炎等過敏性疾病的常用藥物。 由於它能穿透血腦屏障，因此也具有鎮靜和安神的作用，這對於焦慮或極度搔癢且有自殘傾向的動物非常有益。在貓中，由於其解痙和輕度抗焦慮特性，有時也用於管理頻繁復發的自發性下泌尿道疾病 (FLUTD)。
作用機制: Hydroxyzine acts as a competitive antagonist at **H1-receptors** on effector cells. * **Histamine Blockade**: Competes with histamine for H1-receptor sites → prevents histamine-induced bronchoconstriction, vasodilation, and capillary permeability. *Note: It does not inhibit the release of histamine from mast cells, but antagonizes its effects.* * **CNS Effects**: Readily crosses the blood-brain barrier → binds to central H1 receptors → causes sedation and tranquilization. * **Additional Properties**: Exhibits anticholinergic, antispasmodic, local anesthetic, mild bronchodilative, and antiemetic activities. * **Metabolism Pearl**: In vivo, hydroxyzine is metabolized in the liver to its active metabolite, **cetirizine**, which contributes significantly to its prolonged antihistaminic effects.
各物種劑量
- For pruritus · 1-2 mg/kg or 5-10 mg/cat PO q8-12h · PO · q8-12h
- For pruritus · 5-10 mg (total dose) or 2.2 mg/kg PO q8-12h · PO · q8-12h
- For frequently recurrent idiopathic lower urinary tract disease · 5-10 mg (total dose) per cat PO q12h · PO · q12h
- General · 2 mg/kg PO 3 times daily · PO · q8h
- General · 0.5-1 mg/kg IM or PO twice daily · IM/PO · q12h · ARCI UCGFS Class 2 Drug
- General · 0.67 mg/kg PO twice daily · PO · q12h · Using the pamoate salt
- For pruritus associated with allergies, feather picking, or self-mutilation · 2 mg/kg q8h PO or 1.5-2 mg per 4 oz of drinking water daily · PO · q8h or daily · Adjust dose to minimize drowsiness and maximize effect
- For pruritus associated with allergies, feather picking, or self-mutilation · 2 mg/kg PO q12h · PO · q12h
- As an antipruritic/antihistamine · 2.2 mg/kg PO three times daily (q8h) · PO · q8h
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。
給藥途徑
禁忌症
- Hypersensitivity to hydroxyzine or its metabolites (e.g., cetirizine)
- Known hypersensitivity to hydroxyzine or cetirizine
- Early pregnancy (teratogenic in some animal models)
不良反應
- Sedation (most common, usually mild and transient in dogs)
- Hyperexcitability (occasional paradoxical reaction)
- Fine rapid tremors (dogs)
- Whole body tremors (dogs)
- Seizures (rare in dogs)
- Polydipsia (cats)
- Depression (cats)
- Behavioral changes (cats)
- Sedation / Lethargy
- Dry mouth
- Urinary retention
- Gastrointestinal upset
- Paradoxical excitation (rare)
藥物相互作用
- Anticholinergic agents · Additive anticholinergic effects may occur when used concomitantly. · moderate
- CNS Depressant Drugs (e.g., barbiturates, tranquilizers) · Additive CNS depression may be seen.
- Epinephrine · Hydroxyzine may inhibit or reverse the vasopressor effects of epinephrine; use norepinephrine or metaraminol instead.
- CNS Depressants (e.g., opioids, barbiturates, gabapentin) · Additive CNS depression and sedation · major
監測
- Efficacy (reduction in pruritus or clinical signs)
- Adverse effects (degree of sedation, excitability, or behavioral changes)
- Resolution of pruritus or allergic signs
- Degree of sedation
- Adverse anticholinergic effects (e.g., monitoring urination)
過量
Overdoses would be expected to cause **increased sedation** and perhaps **hypotension**. At high doses, fine rapid tremors and rarely seizures have been reported. Common clinical signs of toxicity in dogs include: * Hyperthermia * Lethargy * Tachycardia * Trembling / Tremors * Ataxia * Somnolence **Treatment**: There are no specific antidotes available. Gut emptying protocols should be considered with large or unknown quantity overdoses. Supportive and symptomatic treatment is recommended if necessary.
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。