アルファキサロン
Alfaxalone
3-alpha-hydroxy-5-alpha-pregnane-11,20-dione
別名: Alfaxan-CD RTU · Alfaxan Multidose · alfaksaloni · alfaxalona · alfaxalonum · alphaxalone · GR-2/234
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
監査済み v13 用量エビデンス
確認済み・計算対象外のエビデンス確認済み・計算対象外のエビデンス (10)
エビデンス表示のみ（自動計算対象外）
Crocodilians/induction, but unpredictable results
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 3 mg/kg IV252. Species/Comments: Crocodilians/induction, but unpredictable results.
エビデンス表示のみ（自動計算対象外）
Lizards, chelonians/induction, 35–40 min; duration, 15–35 min; good muscle relaxation; variable results
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 15 mg/kg IM229. Species/Comments: Lizards, chelonians/induction, 35–40 min; duration, 15–35 min; good muscle relaxation; variable results.
エビデンス表示のみ（自動計算対象外）
Most species/good muscle relaxation; variable results; drug requires more evaluation; may have violent recovery;198don’t use within 10 days of DMSO treatment
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 6–9 mg/kg IV, or 9–15 mg/kg IM182. Species/Comments: Most species/good muscle relaxation; variable results; drug requires more evaluation; may have violent recovery;198don’t use within 10 days of DMSO treatment.
エビデンス表示のみ（自動計算対象外）
Horsfield’s tortoises (males only)/light to moderate sedation with no to minimal analgesia; red-eared slider turtles/light sedation of short duration; PD turtles administered 10 mg/kg at low temperature more relaxed than warm, and turtles administered 20 mg/kg at warm temperature were most relaxed
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 10–20 mg/kg IM113,164,300. Species/Comments: Horsfield’s tortoises (males only)/light to moderate sedation with no to minimal analgesia; red-eared slider turtles/light sedation of short duration; PD turtles administered 10 mg/kg at low temperature more relaxed than warm, and turtles administered 20 mg/kg at warm temperature were most relaxed.
エビデンス表示のみ（自動計算対象外）
Turtles, tortoises/induction
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 5 mg/kg IV170. Species/Comments: Turtles, tortoises/induction.
エビデンス表示のみ（自動計算対象外）
Most species
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 6–15 mg/kg IM, IV298. Species/Comments: Most species.
エビデンス表示のみ（自動計算対象外）
Snakes, lizards/induction; not effective for blotched blue-tongued skinks
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 9 mg/kg IV290. Species/Comments: Snakes, lizards/induction; not effective for blotched blue-tongued skinks.
エビデンス表示のみ（自動計算対象外）
Red-eared slider turtles, Eastern painted turtles, yellow-spotted Amazon river turtles, other undocumented turtle species/anesthetic induction
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 20 mg/kg IM141. Species/Comments: Red-eared slider turtles, Eastern painted turtles, yellow-spotted Amazon river turtles, other undocumented turtle species/anesthetic induction.
エビデンス表示のみ（自動計算対象外）
Chelonians (red-eared sliders)/surgical anesthesia with good relaxation
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 24 mg/kg ICe111. Species/Comments: Chelonians (red-eared sliders)/surgical anesthesia with good relaxation.
エビデンス表示のみ（自動計算対象外）
Bearded dragons/effective for induction of anesthesia; respiratory depression noted
TABLE 127.5. Agent: Alfaxalone(Alfaxan, Jurox). Dosage: 12 mg/kg IV262. Species/Comments: Bearded dragons/effective for induction of anesthesia; respiratory depression noted.
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。
概要
アルファキサロン (Alfaxalone) は、速効性の中枢神経系抑制薬および全身麻酔薬として機能する神経活性ステロイド分子です。主に獣医療における麻酔の導入および維持に使用されます。
臨床上のポイントと薬理学的特徴：
- 製剤の進化： 現代の製剤（Alfaxan®）は、可溶化剤として2-ヒドロキシプロピル-β-シクロデキストリン（HPCD）を使用しています。これは、ポリエトキシ化ヒマシ油（Cremophor EL）を含み、特に猫において重篤なヒスタミン放出やアナフィラキシーを引き起こした過去の製品（Saffan®）からの大きな進歩です。
- 心肺機能への影響： 一般的に安全域が広いと考えられていますが、特に急速に静脈内投与した場合、用量依存性の呼吸抑制や導入後の無呼吸を引き起こす可能性があります。代償性の頻脈が起こることはありますが、心血管系のパラメータは通常良好に維持されます。
- 鎮痛作用： アルファキサロンには鎮痛作用がほとんどありません。痛みを伴う処置には、適切な純粋な鎮痛薬（オピオイドなど）を併用する必要があります。
- 回復： 半減期が短く蓄積性がないため、回復は通常迅速かつスムーズですが、刺激を受けたり、前投薬/鎮痛が不十分な場合、精神運動性の興奮（パドリング、発声、痙攣）を経験することがあります。
作用機序
Alfaxalone exerts its anesthetic effects by interacting with GABA_A (gamma-aminobutyric acid type A) receptors in the central nervous system.
- Mechanism: It binds to specific transmembrane domains on the GABA_A receptor complex.
- Pathway: Binding → Enhances the binding of the inhibitory neurotransmitter GABA to the receptor → Increases the frequency and duration of chloride (Cl⁻) ion channel opening → Influx of chloride ions into the neuron → Hyperpolarization of the postsynaptic cell membrane → Inhibition of neural action potential transmission → Dose-dependent CNS depression (ranging from sedation to general anesthesia).
安全性・警告
禁忌
- Concurrent use with other injectable general anesthetic agents (e.g., propofol, thiopental)
- Situations where endotracheal intubation, positive pressure ventilation, and oxygen support are unavailable
- Animals less than 12 weeks of age (safety not established)
有害事象
- Respiratory depression
- Post-induction apnea
- Hypotension (dose-dependent)
- Cardiac arrhythmias (primarily secondary to hypoxemia/hypercapnia)
- Psychomotor excitement during recovery (especially if unstimulated or lacking premedication)
注意事項
Critical Warning: Post-induction apnea is common (up to 44% in dogs, 19% in cats). Alfaxalone should only be used when endotracheal intubation and oxygen supplementation/ventilation are immediately available.
- Administration Rate: Give slowly IV (over 60 seconds or titrated to effect) to minimize the risk of severe apnea.
- Hepatic Dysfunction: Use with caution; lower dosages or increased dosing intervals may be required as the drug undergoes extensive hepatic metabolism.
- Recovery Environment: Keep patients in a quiet, unstimulating environment during recovery to minimize psychomotor excitement. Avoid handling unless necessary.
- Analgesia: Always provide concurrent appropriate pain control, as alfaxalone offers no analgesia.
医薬品相互作用
Potentiates the CNS and respiratory depressant effects. Significantly reduces the required induction and maintenance doses of alfaxalone.
Should not be used concurrently according to the manufacturer label.
Should not be used concurrently according to the manufacturer label.
Increased risk of severe CNS and respiratory depression
Synergistic CNS depression; significantly reduces the required induction dose of alfaxalone
Synergistic CNS depression; reduces the required induction dose of alfaxalone.
Profound synergy; significantly reduces alfaxalone dose requirements and may exacerbate cardiovascular and respiratory depression.
Enhanced sedation and increased risk of hypotension.
Synergistic CNS depression; significantly reduces the required induction dose of alfaxalone.
Synergistic CNS depression; reduces alfaxalone dose requirements.
監視
- Level of anesthesia / CNS depression (jaw tone, palpebral reflex)
- Respiratory rate, rhythm, and depth (capnography and pulse oximetry highly recommended due to apnea risk)
- Cardiovascular status (heart rate, ECG rhythm, blood pressure)
- Body temperature (monitor for hypothermia during anesthesia)
薬物動態
半減期
吸収
Rapid onset following intravenous administration. Well absorbed following deep intramuscular injection in cats.
分布
Widely distributed. Volume of distribution (Vd) in dogs is approximately 2.5 L/kg; in cats, approximately 2 L/kg.
代謝
Undergoes extensive hepatic metabolism via Phase I (cytochrome P450 dependent) and Phase II (conjugation dependent) pathways. Cats form alfaxalone sulfate and alfaxalone glucuronide; dogs form only alfaxalone glucuronide.
消失
Metabolites are eliminated via hepatic/fecal and renal routes. Clearance in dogs is ~54 mL/kg/min. Clearance in cats is dose-dependent (25.1 mL/kg/min at 5 mg/kg; 14.8 mL/kg/min at 25 mg/kg). No clinically relevant accumulation occurs with multiple doses.
過剰投与
Overdoses up to 25 mg/kg primarily result in severe cardiorespiratory depression.
Clinical Signs of Toxicity:
- Severe hypoventilation and prolonged apnea
- Hypotension
- Cardiac arrhythmias
Treatment:
- Immediate endotracheal intubation and positive pressure ventilation with 100% oxygen.
- Cardiovascular support (IV fluids, vasopressors/inotropes if hypotension is severe).
- Continuous monitoring until the drug is metabolized and cleared.
製品
製剤
- 10 mg/mL injection (10 mL and 20 mL vials)
動物用医薬品
- Alfaxan® 10 mg/mL injection (10 mL and 20 mL vials)
規制ステータス
Approved for induction and maintenance of anesthesia.
Prescription Only Medicine - Veterinarian.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store at room temperature (<30°C) and protect from light. Do not freeze. According to the New Zealand label, broached (punctured) vials should preferably be used within 24 hours, but may be stored at 4°C for up to 7 days provided contamination is avoided. Discard if the solution is not clear, colorless, or contains particulate matter.
飼主向け情報
アルファキサロンとは？ アルファキサロンは、手術前に睡眠を導入したり、小手術のために深い鎮静をもたらすために使用される、速効性で安全性の高い注射用麻酔薬です。
期待されること：
- 迅速な作用： 注射後、ペットは非常に早く、スムーズに眠りにつきます。
- モニタリング： 一時的に呼吸が遅くなる可能性があるため、獣医療チームは処置中、ペットの呼吸、心拍数、酸素レベルを注意深く監視します。
- 回復： 処置が終わると、ペットは通常すぐに目を覚まします。ただし、回復期には音、光、接触に敏感になることがあります。驚くと、痙攣したり、足をバタバタさせたり、鳴いたりすることがあります。
- 術後のケア： 獣医スタッフは、ペットが完全に目覚め、足取りがしっかりするまで、静かで暖かく、薄暗い環境で休ませます。退院後、この薬に特化した特別な自宅ケアは必要ありません。
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。