氯雷他定
Loratadine
Ethyl 4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene)-1-piperidinecarboxylate
別名: Clarityn · Claritin · Alavert · Loratadina · Loratadinum
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
各物種劑量
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概覽
氯雷他定 (Loratadine) 是一種第二代、無鎮靜作用的 H1 受體拮抗劑，在獸醫學中主要用於控制過敏性疾病，如異位性皮膚炎、疫苗反應和昆蟲叮咬。與第一代抗組織胺（如苯海拉明）不同，氯雷他定不易穿過血腦屏障，大幅降低了中樞神經系統抑制和鎮靜的發生率。
臨床警告： 務必確保人類非處方氯雷他定產品不含解充血劑（如偽麻黃鹼，通常標示為 'Claritin-D'），因為偽麻黃鹼對犬貓具有高度毒性，可能導致致命的心血管和神經刺激。
作用機制
Loratadine acts as a selective inverse agonist/antagonist at peripheral H1 histamine receptors.
- Histamine Blockade: It competitively binds to H1 receptors on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract → prevents histamine from binding and exerting its pro-inflammatory and vasodilatory effects.
- Non-sedating: Due to its lipophobic nature and large molecular size, it has poor penetration across the blood-brain barrier, resulting in minimal to no central H1 receptor blockade.
安全性與警告
禁忌症
- Known hypersensitivity to loratadine or desloratadine
- Use with caution in patients with severe hepatic impairment
- Use with caution in patients with keratoconjunctivitis sicca (dry eye)
不良反應
- Mild lethargy or sedation (rare compared to first-generation antihistamines)
- Vomiting
- Diarrhea
- Dry mouth (xerostomia)
- Decreased tear production
注意事項
Use with caution in animals with hepatic impairment, as loratadine is extensively metabolized in the liver. Dose adjustments may be necessary.
Allergy Testing: Antihistamines should be withdrawn at least 1 to 2 weeks prior to intradermal allergy testing to prevent false-negative results.
藥物相互作用
May inhibit the metabolism of loratadine, increasing plasma concentrations
May inhibit the metabolism of loratadine, increasing plasma concentrations
May inhibit the metabolism of loratadine, increasing plasma concentrations
May increase loratadine levels via CYP inhibition
監測
- Resolution of allergic clinical signs (e.g., reduced pruritus, erythema)
- Adverse gastrointestinal effects
- Tear production (Schirmer Tear Test) if dry eye is suspected
藥物動力學
半衰期
吸收
Rapidly absorbed from the gastrointestinal tract after oral administration.
分佈
Highly bound to plasma proteins (approx 97%). Poor penetration into the central nervous system.
代謝
Extensively metabolized in the liver via cytochrome P450 enzymes to its major active metabolite, desloratadine.
排除
Excreted roughly equally in urine and feces as metabolites.
過量
Loratadine has a wide margin of safety. Massive overdosage may cause tachycardia, somnolence, and headache.
Treatment: Consists of standard gastrointestinal decontamination (emesis induction, activated charcoal) if ingestion is recent, followed by symptomatic and supportive care. Loratadine is not significantly removed by hemodialysis.
可用產品
劑型
- 10 mg tablet
- 1 mg/ml syrup
人用標示
- 10 mg tablets (GSL)
- 1 mg/ml syrup (GSL)
各地核准狀態
Available OTC for humans.
Available OTC for humans.
Available as a General Sales List (GSL) product in the UK for humans.
暫無法規資料: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store at room temperature (15-30°C) in tight, light-resistant containers. Protect syrup from excessive heat and freezing.
飼主須知
氯雷他定是一種用於治療過敏的抗組織胺藥物。
- 給藥方式： 可與食物一起或空腹給予。如果發生嘔吐，請嘗試與少量食物一起餵食。
- 毒性警告： > 絕對不要給您的寵物服用含有解充血劑的產品（如偽麻黃鹼，常見於 'D' 劑型如 Claritin-D）。這些對寵物具有極高的毒性。
- 預期效果： 對於慢性皮膚過敏，可能需要連續使用幾天才能看到完全的效果。與舊款抗組織胺（如 Benadryl）相比，它通常較少引起嗜睡。
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