氯苯那敏
氯苯那敏是一種第一代烷基胺類抗組織胺藥物，在獸醫學中主要用於其抗組織胺及止癢效果。 **臨床要點：** * **第一代抗組織胺：** 由於能穿透血腦屏障，常會引起中樞神經抑制（嗜睡），有時也利用此特性作為溫和的鎮靜劑。 * **貓咪搔癢症：** 是貓咪治療過敏性皮膚病和搔癢最常用的抗組織胺之一。 * **肥大細胞瘤：** 常作為肥大細胞瘤化療方案的輔助治療，以阻斷全身性組織胺釋放的影響。 * **異常興奮：** 雖然在狗身上通常會引起嗜睡，但貓咪服用後可能會出現異常興奮的反應。
作用機制: Chlorpheniramine acts as a competitive **H1-receptor antagonist**. * **Histamine Blockade:** It competitively inhibits histamine from binding to **H1 receptors** on effector cells (such as smooth muscle and endothelial cells) → prevents histamine-induced vasodilation, increased capillary permeability, and smooth muscle spasms. * **Note:** It does *not* inactivate histamine or prevent its release from mast cells; it only blocks its action at the receptor site. * **Additional Properties:** Like many first-generation antihistamines, it possesses varying degrees of **anticholinergic** (muscarinic blockade) and **CNS depressant** activity.
各物種劑量
- General antihistamine use · 2 mg (total dose) per cat PO every 12 hours · PO · q12h
- General antihistamine use · 2-4 mg per cat q12-24h PO · PO · q12-24h
- General antihistamine use · 2 mg per cat two to three times daily · PO · BID-TID · Most common dosage in cats
- Pruritus · 2-4 mg/cat twice daily; rarely may be maintained on once daily dosing. · PO · BID · Palatability may be enhanced by dipping the split tablet into tuna fish 'juice', butter or petrolatum; placing split tablets into empty gelatin capsules or sprinkling or mixing timed release beads (partial contents of an 8 mg capsule) with food.
- Pruritus · 0.5-2 mg (total dose; ¼ - ½ of a 4 mg tablet) PO 2-3 times per day · PO · BID-TID
- Mild sedative · 1-2 mg per cat q12-24h (low dose), 2-4 mg per cat PO q12-24h (high dose) · PO · q12-24h
- General antihistamine use · 1-2 mg/kg PO 2-3 times a day · PO · BID-TID
- General use / Feather damaging behavior · One 4 mg tablet in one cup (240 mL; 8 oz.) of bottled water to be used as drinking water; changed daily. · PO · q24h
- Adjunctive treatment of chemotherapy of mast cell tumors · 4-8 mg (maximum of 0.5 mg/kg) PO q8-12h PO · PO · q8-12h
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 chlorpheniramine or other alkylamine antihistamines
不良反應
- CNS depression (lethargy, somnolence, sedation)
- GI effects (diarrhea, vomiting, anorexia)
- Anticholinergic effects (dry mouth, urinary retention)
- Paradoxical excitement (especially in cats)
- Decreased performance in working dogs due to sedation
藥物相互作用
- Anticoagulants (heparin, warfarin) · Antihistamines may partially counteract the anticoagulation effects of heparin or warfarin.
- MAO Inhibitors (amitraz, selegiline) · May prolong and exacerbate the anticholinergic effects of the antihistamine.
- CNS Depressants · Increased sedation and CNS depression can occur when used concurrently.
- CNS Depressants (e.g., opioids, sedatives, barbiturates) · Additive CNS depression and sedation · moderate
- Anticholinergic drugs · Additive anticholinergic effects (dry mouth, tachycardia, urinary retention) · moderate
監測
- Clinical efficacy (reduction in pruritus, allergic signs, or adequate sedation)
- Adverse effects (excessive sedation, GI upset, anticholinergic signs)
過量
### Overdose Signs Overdosage may cause **CNS stimulation** (ranging from excitement to seizures) or **CNS depression** (lethargy to coma), anticholinergic effects, respiratory depression, and death. > *Case report:* A 9-month-old dachshund ingesting 25 mg/kg showed signs of ataxia, tremors, bradycardia, coma, and cardiac arrest, dying within 11 hours of ingestion. ### Treatment * **Decontamination:** Empty the gut using standard protocols if ingestion was oral. Induce emesis if the patient is alert and CNS status is stable. Follow with a saline cathartic and/or activated charcoal. * **Supportive Care:** Treat other clinical signs symptomatically. * **Seizure Control:** **Phenytoin (IV)** is recommended in the treatment of seizures caused by antihistamine overdoses in humans; **barbiturates and diazepam should be avoided**.
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。