VetSheet

クレマスチン

Clemastine

Clemastine fumarate

抗ヒスタミン薬（H1受容体拮抗薬）POIV犬猫

別名: Tavist Allergy · Dayhist-1 · Agasten · Aller-Eze · Antihist-1 · Clamist · Contac 12 Hour Allergy · Tavegil · Tavegyl · meclastine fumarate · mecloprodin fumarate · clemastini fumaras · HS-592 · Clemastine fumarate

VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス

0.05-0.1 mg/kg PO q12hPO· q12h
— 🐕

用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。

動物種別用量

🌎 NA — North America🌍 EU — Europe

犬

適応用量経路頻度期間地域
Allergic conditions (Historical dosing - Efficacy doubtful)0.05-0.1 mg/kg PO q12hPOq12h—🌎 NA
  • Allergic conditions (Historical dosing - Efficacy doubtful): 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.

猫

適応用量経路頻度期間地域
Antihistamine0.68 mg per cat PO twice dailyPOq12h—🌎 NA
Antihistamine0.34-0.68 mg per cat PO q12hPOq12h—🌎 NA
Atopy0.15 mg/kg PO q 12 hrsPOq12h—🌎 NA
  • Atopy: Efficacy may be increased by combining with omega 3 fatty acids.

用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。

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概要

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.

安全性・警告

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)

注意事項

Use with caution in patients with prostatic hypertrophy, bladder neck obstruction, severe cardiac failure, angle-closure glaucoma, or pyeloduodenal obstruction. Antihistamines should be discontinued 3-7 days before intradermal skin testing to prevent false-negative wheal and flare responses. Use with caution in pregnant or nursing animals, especially with newborns, as the drug enters maternal milk.

医薬品相互作用

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)Moderate

Additive CNS depression and sedation

Anticholinergic drugsModerate

Additive anticholinergic effects (dry mouth, urinary retention)

監視

  • Clinical efficacy (reduction in pruritus, allergic signs)
  • Adverse effects (sedation, hyperactivity, anticholinergic signs)

薬物動態

半減期

馬5.4 hours (terminal)犬4 hours (IV)

吸収

Dogs: Very low oral bioavailability (3%). Horses: Poor oral bioavailability (3-4%). Humans: Variable bioavailability (20-70%).

分布

Dogs: High volume of distribution (13.4 L/kg); 98% protein bound. Horses: Volume of distribution at steady-state is 3.8 L/kg. Distributes into milk.

代謝

Appears to be extensively metabolized (based on human data).

消失

Metabolites are eliminated in the urine. Clearance in dogs: 2.1 L/hr/kg. Clearance in horses: 0.79 L/hr/kg.

過剰投与

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.

製品

製剤

  • Oral tablets
  • Oral syrup

ヒト用医薬品

  • Clemastine Fumarate Oral Tablets: 1.34 mg (equivalent to 1 mg clemastine), 2.68 mg (equivalent to 2 mg clemastine)
  • Clemastine Oral Syrup: 0.67 mg/5 mL (equivalent to 0.5 mg clemastine)

規制ステータス

European Union✓ 承認済みEMA

Available as a human product used off-label in veterinary medicine.

United Kingdom✓ 承認済みVMD

Classified as GSL (General Sales List) in the UK, meaning it can be sold without a prescription.

規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

保管・安定性

Oral tablets and solution should be stored in tight, light-resistant containers at room temperature.

飼主向け情報

抗ヒスタミン薬はアレルギー症状の緩和に役立ちますが、根本的な疾患を治癒するものではありません。ペットに眠気や異常な興奮を引き起こすことがあり、口の渇きが見られることもあります。猫では下痢がよく見られます。必ず獣医師の指示に従って投与してください。

VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。