ナロキソン
Naloxone
Naloxone hydrochloride, N-allylnoroxymorphone
別名: Narcan · N-allylnoroxymorphone · naloxona · EN-15304 · naloxoni · Naloxonum · Naloxone hydrochloride
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 (2)
エビデンス表示のみ（自動計算対象外）
Green tree monitors/reversal of butorphanol
TABLE 127.5. Agent: Naloxone. Dosage: 4 mg/kg IM95. Species/Comments: Green tree monitors/reversal of butorphanol.
エビデンス表示のみ（自動計算対象外）
Corn snakes, bearded dragons, red-eared sliders/µ-opioid agonist reversal
TABLE 127.5. Agent: Naloxone. Dosage: 0.04–2 mg/kg SC304,305,307,309. Species/Comments: Corn snakes, bearded dragons, red-eared sliders/µ-opioid agonist reversal.
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
ナロキソンは純粋なオピオイド拮抗薬であり、獣医療では主にオピオイド作動薬の作用（呼吸抑制、鎮静、不快気分など）を逆転させるために使用されます。オピオイド過剰摂取時の救命解毒剤です。
主な用途以外にも、各種ショック（敗血症性、循環血液量減少性、心原性）の治療や、内因性エンドルフィンを阻害することによる尾追いなどの自傷行為の抑制についても研究されています。
臨床のポイント: ナロキソン自体には鎮痛作用はありません。オピオイドによる呼吸抑制を逆転させるために使用すると、同時にオピオイドの鎮痛効果も逆転させるため、突然痛みが戻り、カテコールアミンの放出を引き起こす可能性があります。
作用機序
Naloxone acts as a competitive antagonist at opioid receptors. It binds primarily to the mu (μ) receptor, but also has affinity for kappa (κ) and sigma (σ) receptors.
By occupying these receptors without activating them, it displaces opioid agonists → rapid reversal of opioid-induced respiratory and CNS depression.
At very high doses, naloxone may exhibit additional pharmacologic activity, including GABA antagonism and the ability to increase dopamine levels.
安全性・警告
禁忌
- Hypersensitivity to naloxone
- Indiscriminate use in animals that have undergone major surgery or trauma (due to severe pain from analgesia reversal)
有害事象
- Reversal of analgesia (return of pain)
- Acute withdrawal syndrome in opioid-dependent patients
- CNS excitement (especially if used in meperidine overdose)
- Seizures (at very high doses, likely secondary to GABA antagonism)
- Acute severe discomfort or pain (due to sudden loss of analgesia)
- Antanalgesic effects in opioid-naïve subjects
- Transient elevation of unconsciousness (at low doses)
注意事項
Important Warning: The duration of action of naloxone (45-90 minutes) is often shorter than the opioid it is reversing. Patients may slip back into respiratory depression and require re-dosing or continuous ventilatory support.
- Use with caution in animals with preexisting cardiac abnormalities.
- Use cautiously in opioid-dependent animals or those that have received exceedingly large doses of narcotics, as it may precipitate an acute withdrawal syndrome.
- Meperidine Toxicity: Naloxone is reportedly not effective for reversing meperidine-induced seizures and may elicit CNS excitement if normeperidine excitotoxicity is present. Avoid unless severe respiratory depression is present without ventilatory support.
- Buprenorphine: Naloxone is not a good reversal agent for buprenorphine due to buprenorphine's high receptor affinity; massive doses (100X usual) may be required.
医薬品相互作用
Naloxone may antagonize the effects of these agents (respiratory depression, analgesia). It should not be relied upon to treat respiratory depression caused by buprenorphine.
Naloxone may reduce the hypotensive and bradycardic effects of clonidine; potentially useful for clonidine overdoses.
Naloxone may increase the CNS effects of yohimbine (anxiety, tremors, nausea, palpitations) and increase plasma cortisol levels.
Naloxone reverses the analgesic, sedative, and respiratory depressant effects of opioid agonists.
Buprenorphine binds tightly to opioid receptors; naloxone may not fully reverse its effects or may require much higher doses.
監視
- Respiratory rate and depth
- CNS function (level of sedation/arousal)
- Pain associated with opiate reversal
- Respiratory rate and effort
- Level of consciousness / sedation score
- Pain score (monitor for acute pain upon reversal)
- Heart rate and blood pressure
薬物動態
半減期
吸収
Minimally absorbed orally (rapidly destroyed in the GI tract). Very rapid onset of action when given IV (1-2 minutes). IM onset is generally within 5 minutes. Duration of action usually persists from 45-90 minutes, but may act for up to 3 hours.
分布
Distributed rapidly throughout the body with high levels found in the brain, kidneys, spleen, skeletal muscle, lung, and heart. Readily crosses the placenta.
代謝
Metabolized in the liver, principally via glucuronidative conjugation.
消失
Metabolites are excreted into the urine.
過剰投与
Naloxone is considered a very safe agent with a very wide margin of safety. However, massive overdoses have initiated seizures in a few patients, which is theorized to be secondary to GABA antagonism.
製品
製剤
- Injection: 0.4 mg/mL
- Neonatal Injection: 0.02 mg/mL
- Injectable: 0.02 mg/ml solution
- Injectable: 0.4 mg/ml solution
動物用医薬品
- Naloxone 0.02 mg/ml injectable solution
- Naloxone 0.4 mg/ml injectable solution
ヒト用医薬品
- Naloxone HCl Injection: 0.4 mg/mL (400 micrograms/mL) in 1 mL amps, syringes and 1 mL, 2 mL, & 10 mL vials (Narcan)
- Naloxone HCl Neonatal Injection: 0.02 mg/mL in 2 mL vials
- Narcan 0.4 mg/ml injectable solution
- Narcan nasal spray
規制ステータス
POM (Prescription Only Medicine)
POM-V
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store at room temperature (15-30°C) and protect from light. Sterile water for injection is the recommended diluent. When given as an IV infusion, either D5W or normal saline should be used. Do not mix with solutions containing sulfites, bisulfites, long-chain or high molecular weight anions, or any solutions at alkaline pH.
飼主向け情報
- 目的: ナロキソンは、オピオイド系鎮痛薬の作用を逆転させたり、過剰摂取を治療したりするための緊急用薬剤です。
- 期待されること: ペットは鎮静状態からすぐに目覚めることがあります。鎮痛薬の効果を打ち消すため、突然痛みが戻る可能性があります。
- モニタリング: ナロキソンの効果はオピオイドよりも早く切れることがあります。極度の眠気や呼吸の遅れ、反応の鈍さが再び現れないか、ペットを注意深く観察してください。
- 投与: 通常は獣医療従事者が投与しますが、場合によっては（生まれたばかりの子犬/子猫など）、舌の下に1滴垂らすよう指示されることがあります。
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。