クレマスチン
クレマスチンは、アレルギー症状の緩和に使用される第一世代のエタノールアミン系抗ヒスタミン薬です。抗コリン作用が強い一方で、鎮静作用は比較的弱いという特徴があります。犬や馬では経口バイオアベイラビリティが非常に低く、経口投与による有効性には疑問が残ります。
作用機序: Like other first-generation antihistamines, clemastine acts as a competitive antagonist (or inverse agonist) at **H1-receptors**. * **Mechanism:** Competes with histamine for H1-receptor sites on effector cells (smooth muscle, endothelium, CNS) → prevents histamine-induced bronchoconstriction, vasodilation, and increased capillary permeability. * **Note:** It does *not* block the release of histamine from mast cells or basophils, but rather antagonizes its downstream effects. * Exhibits significant **anticholinergic (antimuscarinic)** activity, which contributes to both its drying effects on mucous membranes and potential side effects.
動物種別の用量
- Antihistamine · 0.68 mg per cat PO twice daily · PO · q12h
- Antihistamine · 0.34-0.68 mg per cat PO q12h · PO · q12h
- Atopy · 0.15 mg/kg PO q 12 hrs · PO · q12h · Efficacy may be increased by combining with omega 3 fatty acids.
- Allergic conditions (Historical dosing - Efficacy doubtful) · 0.05-0.1 mg/kg PO q12h · PO · q12h · Oral bioavailability is <5%. An oral dose of 0.5 mg/kg only slightly inhibited wheal formation. Further dosing studies are needed before recommending therapeutic oral use.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Known hypersensitivity to clemastine
有害事象
- Sedation (dogs)
- Paradoxical hyperactivity (dogs)
- Anticholinergic effects: dry mucous membranes, tachycardia, urinary retention
- Diarrhea (cats)
- Fixed drug reaction (cats - rare)
薬物相互作用
- CNS Depressant Medications (e.g., barbiturates, tranquilizers) · Additive CNS depression may occur.
- Monoamine Oxidase Inhibitors (e.g., furazolidone, amitraz, selegiline) · May intensify the anticholinergic effects of clemastine.
- CNS Depressants (e.g., phenobarbital, gabapentin, opioids) · Additive CNS depression and sedation · moderate
- Anticholinergic drugs · Additive anticholinergic effects (dry mouth, urinary retention) · moderate
モニタリング
- Clinical efficacy (reduction in pruritus, allergic signs)
- Adverse effects (sedation, hyperactivity, anticholinergic signs)
過量投与
There are no specific antidotes for clemastine overdose. * **Management:** Handle significant overdoses using standard gut-emptying protocols (emesis/gastric lavage) when appropriate, followed by supportive therapy. * **Clinical Signs:** Overdose signs are extensions of the drug's side effects, principally **CNS depression** (though CNS stimulation/seizures may occur), severe **anticholinergic effects** (severe drying of mucous membranes, tachycardia, urinary retention, hyperthermia), and possibly hypotension. * **Specific Treatments:** **Physostigmine** may be considered to treat serious CNS anticholinergic effects. **Diazepam** can be employed to treat seizures if necessary.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。