メデトミジン
Medetomidine
Medetomidine Hydrochloride
別名: Domitor · Dorbene · Dormilan · Medetor · Sedastart · Sedator · Sededorm · MPV-785 · Medetomidine 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
構造化された用量計算エビデンスRefractory seizures (extra-label)
認証済み獣医師の確認が必要
NA
必ず考慮する臨床コンテキスト (7)
- 1. Medetomidine dosages depend on the combination of drugs used and the dosage(s) of the other drug(s). Dosage adjustments will also need to be made to account for the degree of desired sedation; type, duration, and pain level of the procedure, and patient temperament and body weight/size.
- 3. Premedication with medetomidine will significantly reduce the dose of the induction agent required and will reduce volatile anesthetic requirements for maintenance anesthesia. All anesthetic agents used for induction or maintenance of anesthesia should be administered to effect.
- 4. For all dosages, the low end of the dose range is generally appropriate for IV administration, whereas the mid-upper range is most appropriate for IM or SC administration. Higher dosages will provide more profound sedation and analgesia.
- 5. When SC administration is used, the speed of sedation is slower, and the level of sedation is lighter and inconsistent. For more predictable sedation, IM or IV administration is recommended.
- 6. The effects of medetomidine can be reversed with atipamezole.
- It is most often dosed by volume at ½ or same volume of medetomidine that was administered and given IM. See Atipamezole.
- The commercially available injection should be stored at room temperature (15°C-30°C [59°F-86°F]) and protected from freezing. Use within 28 days of first vial puncture.
確認済み・計算対象外のエビデンス (1)
エビデンス表示のみ（自動計算対象外）
Light sedation (often also used for pre-anesthesia)
a) Light sedation (often also used for pre-anesthesia): 5 – 20 µg/kg IM, IV, SC 18
必ず考慮する臨床コンテキスト (7)
- 1. Medetomidine dosages depend on the combination of drugs used and the dosage(s) of the other drug(s). Dosage adjustments will also need to be made to account for the degree of desired sedation; type, duration, and pain level of the procedure, and patient temperament and body weight/size.
- 3. Premedication with medetomidine will significantly reduce the dose of the induction agent required and will reduce volatile anesthetic requirements for maintenance anesthesia. All anesthetic agents used for induction or maintenance of anesthesia should be administered to effect.
- 4. For all dosages, the low end of the dose range is generally appropriate for IV administration, whereas the mid-upper range is most appropriate for IM or SC administration. Higher dosages will provide more profound sedation and analgesia.
- 5. When SC administration is used, the speed of sedation is slower, and the level of sedation is lighter and inconsistent. For more predictable sedation, IM or IV administration is recommended.
- 6. The effects of medetomidine can be reversed with atipamezole.
- It is most often dosed by volume at ½ or same volume of medetomidine that was administered and given IM. See Atipamezole.
- The commercially available injection should be stored at room temperature (15°C-30°C [59°F-86°F]) and protected from freezing. Use within 28 days of first vial puncture.
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
メデトミジンは、強力な合成α2アドレナリン受容体作動薬であり、その深い鎮静、鎮痛、および筋弛緩作用のため獣医療で広く使用されています。
主な臨床的特徴は以下の通りです：
- 二相性の心血管反応：初期の末梢血管収縮により一過性の高血圧が生じ、その後反射性徐脈および正常血圧または軽度の低血圧に移行します。
- 可逆性：その効果は、アチパメゾールなどの特異的α2拮抗薬を使用して迅速かつ完全に拮抗（リバース）させることができます。
- 立体化学：メデトミジンは2つの立体異性体のラセミ混合物です。活性エナンチオマーはデクスメデトミジンであり、現代の多くの獣医療市場においてラセミ体のメデトミジンに取って代わられつつあります。
- 相乗効果：オピオイド、ケタミン、その他の麻酔薬と高い相乗効果を示し、併用する麻酔薬の用量を大幅に減らすことができます。
臨床のポイント：優れた体性および内臓鎮痛を提供しますが、鎮静効果は通常、鎮痛効果よりも長く持続します。深く鎮静しているように見えても、大きな音や乱暴な扱いによって突然覚醒することがあります。
作用機序
Medetomidine produces its effects by binding to and activating pre- and postsynaptic alpha-2 adrenergic receptors in the central and peripheral nervous systems.
- Central Nervous System: Activation of alpha-2 receptors in the locus coeruleus → inhibition of adenylyl cyclase → decreased cAMP → efflux of potassium (hyperpolarization) → decreased release of norepinephrine. This suppression of sympathetic outflow results in profound sedation, anxiolysis, and analgesia.
- Cardiovascular System: Activation of peripheral alpha-1 and alpha-2b receptors in vascular smooth muscle → profound vasoconstriction → increased systemic vascular resistance (hypertension) → baroreceptor-mediated increased vagal tone → reflex bradycardia.
- Endocrine/Metabolic: Inhibits insulin release from pancreatic beta cells → transient hyperglycemia. Decreases antidiuretic hormone (ADH) release → increased diuresis.
Medetomidine is highly selective, with an alpha-2:alpha-1 selectivity ratio of 1620:1 (approximately 10 times more specific than xylazine).
安全性・警告
禁忌
- Cardiac disease
- Respiratory disorders
- Liver or kidney diseases
- Shock or severe debilitation
- Animals stressed due to heat, cold, or fatigue
- Pregnancy (insufficient safety data; use only if benefits clearly outweigh risks)
- Cardiovascular disease
- Systemic disease
- Geriatric patients
- Pregnant animals
- Conditions where vomiting is contraindicated (e.g., gastrointestinal foreign body, raised intraocular pressure)
- Diabetes mellitus
有害事象
- Bradycardia (often profound)
- Atrioventricular (AV) blocks
- Decreased respiratory rate and potential apnea
- Hypothermia
- Increased urination (diuresis)
- Vomiting (especially in cats)
- Pain on intramuscular injection
- Blanched or cyanotic mucous membranes (due to peripheral vasoconstriction)
- Rarely: prolonged sedation, paradoxical excitation, hypersensitivity, death from circulatory failure
- Decreased cardiac output
- Initial hypertension followed by normotension/hypotension
- Vomiting (especially common after IM administration)
- Diuresis (due to ADH suppression)
- Transient hyperglycemia (due to decreased insulin)
- Mydriasis
- Decreased intraocular pressure
- Spontaneous arousal from deep sedation
注意事項
- Agitated Patients: Dogs that are extremely agitated or excited may have a decreased response due to high circulating catecholamines overriding the receptor. Allow dogs to rest quietly before administration. Do not re-dose if they fail to respond.
- Age Extremes: Use with extreme caution in very young or geriatric animals due to reduced cardiovascular reserve.
- Hematologic: Medetomidine can inhibit ADP-induced platelet aggregation.
- Reversal: Treat medetomidine-induced bradycardia or excessive sedation with atipamezole rather than anticholinergics.
医薬品相互作用
Controversial. Using anticholinergics to treat medetomidine-induced bradycardia can lead to severe hypertension, increased myocardial work, and arrhythmias. Concomitant use is generally discouraged, especially at higher medetomidine doses (>20 mcg/kg).
Synergistic enhancement of sedation and analgesia. Adverse cardiovascular and respiratory effects may also be pronounced. Reduced dosages and careful monitoring are advised.
When used after medetomidine, severe hypoxemia may occur. Significant dosage reductions of propofol are required along with adequate respiratory monitoring.
May reverse the effects of medetomidine, but atipamezole is the preferred and more specific reversal agent.
Significantly reduces the dose required for induction and maintenance of anesthesia.
Reduces the dose required to maintain anesthesia by up to 70%.
Contraindicated; may cause severe cardiovascular complications.
Synergistic sedation and analgesia (beneficial interaction).
監視
- Level of sedation and analgesia
- Heart rate and rhythm (ECG recommended in high-risk patients)
- Body temperature (monitor for hypothermia)
- Respiratory rate and depth
- Pulse oximetry (SpO2)
- Heart rate and rhythm (bradycardia is expected, but monitor for severe arrhythmias)
- Blood pressure (initial hypertension followed by normotension/hypotension)
- Oxygen saturation (SpO2)
- Body temperature (risk of hypothermia due to reduced metabolic rate and peripheral vasoconstriction)
- Depth of sedation
薬物動態
半減期
吸収
Rapid onset after IV (5 minutes) or IM (10-15 minutes) injection. SC absorption is unreliable. Can be absorbed via oral mucosa (sublingually) but efficacy may be lower than IM.
分布
Highly lipophilic, allowing rapid penetration of the blood-brain barrier to exert central effects.
代謝
Undergoes extensive hepatic biotransformation.
消失
Metabolites are primarily excreted via the kidneys.
過剰投与
Single doses of up to 5X (IV) and 10X (IM) have been tolerated in dogs, though severe adverse effects (profound bradycardia, AV blocks, respiratory depression) can occur. Death has occurred rarely in dogs (1 in 40,000) receiving 2X doses.
Important: Treatment of medetomidine-induced bradycardia with anticholinergic agents (atropine or glycopyrrolate) is not recommended due to the risk of severe hypertension, increased myocardial oxygen demand, and arrhythmias.
Atipamezole (an alpha-2 antagonist) is the safest and most effective choice to reverse medetomidine-induced cardiovascular and sedative effects.
製品
製剤
- Injection: 1 mg/mL in 10 mL multidose vials
- Injectable: 1 mg/ml solution
動物用医薬品
- Medetomidine HCl for Injection: 1 mg/mL in 10 mL multidose vials (Domitor®)
- Domitor 1 mg/ml solution for injection
- Dorbene 1 mg/ml solution for injection
- Dormilan 1 mg/ml solution for injection
- Medetor 1 mg/ml solution for injection
- Sedastart 1 mg/ml solution for injection
- Sedator 1 mg/ml solution for injection
- Sededorm 1 mg/ml solution for injection
規制ステータス
Classified as POM-V.
Classified as POM-V.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store commercially available injection at room temperature (15-30°C) and protect from freezing.
飼主向け情報
- 専門家による使用のみ：この薬は強力な鎮静剤および麻酔補助薬であり、獣医療従事者によってのみ投与および監視されるべきです。
- 予想される外見：鎮静中、ペットの心拍数は著しく低下し、歯茎が青白くまたは少し青みがかって見えることがあります。これは薬の予想される効果であり、獣医療チームが注意深く監視しています。
- 安静を保つ：ペットが深く眠っているように見えても、突然の大きな音や乱暴な扱いで驚いて目を覚ますことがあります。回復中は環境を静かで穏やかに保ってください。
- 拮抗薬（リバーサル）：処置後、獣医師はペットを迅速かつスムーズに目覚めさせるために「拮抗薬」（アチパメゾール）を投与することがあります。
- リスクのあるペット：ペットに心臓、肝臓、腎臓の持病がある場合、または妊娠している場合は、この薬の使用が安全でない可能性があるため、必ず獣医師に伝えてください。
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。