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ハロタン

Halothane

2-bromo-2-chloro-1,1,1-trifluoroethane

吸入全身麻酔薬InhalationInhalational犬猫小型哺乳類鳥馬

別名: Fluothane · Ineltano · phthorothanum · Halothanum

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

3% (induction); 0.5-1.5% (maintenance)Inhalation· Continuous· As needed for procedure

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
General Anesthesia3% (induction); 0.5-1.5% (maintenance)InhalationContinuousAs needed for procedure🌎 NA
General Anesthesia0.5-3.5%, inhaledInhalationContinuousAs needed for procedure🌎 NA
Induction of anaesthesia (unpremedicated)3-4% concentrationInhalationalContinuousUntil induced🌍 EU
Maintenance of anaesthesia0.8-1.0% (MAC)InhalationalContinuousDuration of procedure🌍 EU
  • General Anesthesia: Concentrations are dependent upon fresh gas flow rate.
  • Induction of anaesthesia (unpremedicated): Delivered via calibrated vaporizer
  • Maintenance of anaesthesia: Adjust according to individual requirement and concurrent drugs

猫

適応用量経路頻度期間地域
General Anesthesia3% (induction); 0.5-1.5% (maintenance)InhalationContinuousAs needed for procedure🌎 NA
General Anesthesia0.5-3.5%, inhaledInhalationContinuousAs needed for procedure🌎 NA
Induction of anaesthesia (unpremedicated)3-4% concentrationInhalationalContinuousUntil induced🌍 EU
Maintenance of anaesthesia0.8-1.0% (MAC)InhalationalContinuousDuration of procedure🌍 EU
  • General Anesthesia: Concentrations are dependent upon fresh gas flow rate.
  • Induction of anaesthesia (unpremedicated): Delivered via calibrated vaporizer
  • Maintenance of anaesthesia: Adjust according to individual requirement and concurrent drugs

小型哺乳類

適応用量経路頻度期間地域
General Anesthesia (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas)Induction: 2%-4%, maintenance: 0.25%-2%InhalationContinuousAs needed for procedure🌎 NA
  • General Anesthesia (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas): Using a non-rebreathing system.

鳥

適応用量経路頻度期間地域
General Anesthesia2% (small birds) or 2.5%-3% (large birds) for induction; 0.5%-1.5% for maintenanceInhalationContinuousAs needed for procedure🌎 NA
  • General Anesthesia: Induction usually occurs in 2-4 minutes. Recovery takes 3-5 minutes. Bradycardia, hypotension, and hypothermia may occur but rapidly resolve upon discontinuation.

馬

適応用量経路頻度期間地域
General Anesthesia (Draft Horses)4%-5% initially, maintenance 2.5%-3%InhalationContinuousAs needed for procedure🌎 NA
  • General Anesthesia (Draft Horses): Administered in an oxygen-enriched semi-closed large animal circle system. Reduce as indicated by physical monitoring.

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。

診察中ですか？VetSheet の AI が薬剤・用量・投与期間を構造化された診察記録に直接記入します。VetSheet の仕組みを見る

概要

ハロタンは古典的な​ハロゲン化吸入全身麻酔薬​であり、その強力な作用、制御のしやすさ、および不燃性から、かつては獣医療における主要な麻酔薬でした。

現代の獣医麻酔の基礎を築きましたが、現在では多くの国で​ほぼ時代遅れとなり、市販されていません​。心血管抑制や肝毒性の観点からより安全性の高い新しい薬剤（​イソフルラン​、​セボフルラン​、​デスフルラン​など）に広く取って代わられています。

​臨床のポイント:​

  • 現代の吸入麻酔薬と比較して血液ガス分配係数が高いため、導入および覚醒に時間がかかります。
  • 心筋をカテコールアミンに対して感作させるという特有の性質があり、心室性不整脈のリスクを著しく高めます。
  • 薬物の約12%が肝臓で代謝されるため（イソフルランは1%未満）、免疫介在性肝毒性（ハロタン肝炎）を引き起こすリスクがあります。

作用機序

The exact mechanism of inhalant anesthetics remains incompletely understood, but involves multiple central nervous system targets:

  • ​Lipid Matrix Interaction:​ Historically explained by the Meyer-Overton rule, halothane interacts with the lipid bilayer of neuronal membranes, disrupting normal ion channel function.
  • ​Receptor Modulation:​ Modern evidence suggests halothane acts via positive allosteric modulation of inhibitory receptors (such as GABA_A and glycine receptors) → enhancing CNS depression.
  • ​Excitatory Inhibition:​ It simultaneously inhibits excitatory receptors (such as NMDA and nicotinic acetylcholine receptors) → dampening neuronal excitability.

​Systemic Effects:​

  • Profound CNS depression and blunting of thermoregulatory centers.
  • Increased cerebral blood flow.
  • Dose-dependent respiratory depression (especially pronounced in ruminants).
  • Significant myocardial depression, vasodilation, and hypotension.

安全性・警告

禁忌

  • History or predilection towards malignant hyperthermia
  • Significant hepatotoxicity or unexplained fever/jaundice after previous halothane exposure
  • Liver disease
  • Patients with a history of malignant hyperthermia

有害事象

  • Dose-related hypotension
  • Cardiac depression and decreased cardiac output
  • Cardiac dysrhythmias (sensitizes myocardium to catecholamines)
  • Malignant hyperthermia-stress syndrome (reported in pigs, horses, dogs, cats)
  • Hepatotoxicity (jaundice, fatal liver necrosis)
  • Respiratory depression
  • Hypothermia
  • Dose-dependent hypotension
  • Bradycardia
  • Decreased myocardial contractility
  • Reduced hepatic blood flow
  • Ventricular arrhythmias
  • Neonatal depression (crosses placental barrier)

注意事項

​Hepatotoxicity Warning:​ Halothane can cause severe, sometimes fatal, liver necrosis. Do not re-expose patients who have previously shown unexplained fever or jaundice following halothane anesthesia.

  • ​Cardiovascular/Neurologic:​ Use with extreme caution in patients with cardiac arrhythmias, hepatic impairment, increased intracranial pressure (CSF) or head injury, myasthenia gravis, or pheochromocytoma.
  • ​Pregnancy:​ Categorized as Class C. May be teratogenic; use only when benefits clearly outweigh potential risks.
  • ​Equipment:​ Halothane vapor can react with aluminum, brass, and lead in the presence of moisture. It also causes rapid deterioration of rubber and some plastics.

医薬品相互作用

Acetaminophen

Not recommended for post-operative analgesia in patients that have received halothane anesthesia due to increased risk of hepatotoxicity.

Acepromazine

Can decrease requirements of halothane by up to 40%.

Aminoglycosides

Use with caution; additive neuromuscular blockade may occur.

Lincosamides

Use with caution; additive neuromuscular blockade may occur.

Non-depolarizing neuromuscular blocking agents

Additive neuromuscular blockade may occur.

Succinylcholine

May induce increased incidences of cardiac effects (bradycardia, arrhythmias, sinus arrest, apnea) and malignant hyperthermia in susceptible patients.

Sympathomimetics (dopamine, epinephrine, norepinephrine, ephedrine, metaraminol)

Halothane sensitizes the myocardium to catecholamines; severe ventricular arrhythmias may result. Use with extreme caution at reduced doses.

d-Tubocurarine

May cause significant hypotension if used with halothane.

SedativesModerate

Reduces the concentration of halothane required to achieve surgical anaesthesia

Opioid agonistsModerate

Reduces the concentration of halothane required to achieve surgical anaesthesia

Nitrous oxide (N2O)Moderate

Reduces the concentration of halothane required to achieve surgical anaesthesia

CatecholaminesMajor

Facilitates the generation of ventricular arrhythmias

監視

  • Respiratory and ventilatory status
  • Cardiac rate and rhythm (ECG is highly recommended due to arrhythmogenic potential)
  • Blood pressure (especially in 'at risk' patients)
  • Level of anesthetic depth
  • Body temperature (monitor for hypothermia or malignant hyperthermia)
  • Heart rate and rhythm (ECG)
  • Respiratory rate and depth
  • Capnography (ETCO2)
  • Anaesthetic depth (jaw tone, palpebral reflex)

薬物動態

吸収

Rapidly absorbed through the lungs into the systemic circulation.

分布

Highly lipid soluble; distributes widely into tissues including the CNS. Distributed into milk.

代謝

Approximately 12% of the absorbed drug is metabolized by the liver to trifluoroacetic acid, chlorine, and bromine radicals.

消失

The bulk of the absorbed drug is re-excreted by the lungs and eliminated with expired air. Hepatic metabolites are excreted in the urine.

過剰投与

Overdosage of halothane results in profound cardiopulmonary depression, characterized by severe hypotension, bradycardia, arrhythmias, and apnea.

​Treatment:​

  1. Immediately turn off the anesthetic vaporizer.
  2. Flush the breathing circuit with 100% oxygen.
  3. Institute positive pressure ventilation.
  4. Provide cardiovascular support (e.g., IV fluid volume expansion, positive inotropes like dobutamine, and anticholinergics for bradycardia).
  5. Lidocaine may be required to treat halothane-induced ventricular dysrhythmias.

製品

製剤

  • Inhalation liquid (vaporized for administration)
  • Inhalational liquid: 250 ml bottle

動物用医薬品

  • Fluothane 250 ml bottle
  • Halothane POM-V 250 ml bottle

規制ステータス

European Union✓ 承認済み処方箋医薬品EMA
🐕 Dogs🐈 Cats

POM-V classification.

United Kingdom✓ 承認済み処方箋医薬品VMD
🐕 Dogs🐈 Cats

POM-V classification.

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

保管・安定性

Store below 40°C in a tight, light-resistant container. Halothane stability is maintained by the addition of thymol and ammonia. Thymol does not vaporize and may accumulate in the vaporizer, causing a yellow discoloration (do not use discolored solutions). In the presence of moisture, halothane vapor reacts with aluminum, brass, and lead. It also causes rapid deterioration of rubber and some plastics.

飼主向け情報

ハロタンは、手術中に動物を無意識かつ無痛の状態に保つために使用される​吸入麻酔ガス​です。

  • ​現代での使用:​ 過去には非常に一般的でしたが、現在の動物病院では主に新しく安全な麻酔ガスが使用されています。もしハロタンが使用される場合、獣医師がペットの特定の状況に適切であると判断したためです。
  • ​リスク:​ 他の全身麻酔と同様に、血圧低下、心拍リズムの変化、体温低下などのリスクが伴います。獣医療チームは手術中、ペットのバイタルサインを注意深く監視します。
  • ​麻酔後:​ 帰宅後1〜2日は、ペットがぼんやりしたり眠たそうにしたりすることがあります。回復するまでは、暖かく静かで安全な環境に置いてあげてください。
  • ​注意事項:​ 過去に麻酔で副作用（特に原因不明の発熱や肝臓の問題）を起こしたことがある場合は、必ず獣医師にお知らせください。

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