美托咪啶
Medetomidine
Medetomidine Hydrochloride
別名: Domitor · Dorbene · Dormilan · Medetor · Sedastart · Sedator · Sededorm · MPV-785 · Medetomidine hydrochloride
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
經審核的 v13 劑量證據
結構化劑量計算證據Refractory seizures (extra-label)
須由已驗證獸醫確認
NA
必須同時考慮的臨床上下文 (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.
經審核的非計算證據 (1)
只供證據參考，不會自動計算
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
必須同時考慮的臨床上下文 (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.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
概覽
美托咪啶 (Medetomidine) 是一種強效的合成 Alpha-2 腎上腺素受體激動劑，在獸醫學中廣泛用於其深度的鎮靜、鎮痛和肌肉鬆弛特性。
主要臨床特徵包括：
- 雙相心血管反應：初期的周邊血管收縮導致短暫的高血壓，隨後引發反射性心搏過緩及隨後的血壓正常或輕微低血壓。
- 可逆性：其作用可透過特定的 Alpha-2 拮抗劑（如 阿替美唑 Atipamezole）迅速且完全地逆轉。
- 立體化學：美托咪啶是兩種立體異構物的消旋混合物。其活性對映異構體為 右美托咪啶 (Dexmedetomidine)，目前在許多現代獸醫市場中已大幅取代消旋美托咪啶。
- 協同作用：與鴉片類藥物、氯胺酮 (Ketamine) 及其他麻醉劑具有高度協同作用，可顯著降低併用麻醉劑的劑量。
臨床要點：雖然它能提供極佳的體表與內臟鎮痛效果，但鎮靜作用的時間通常長於鎮痛作用。如果受到巨大噪音或粗魯操作的刺激，即使病患看起來處於深度鎮靜狀態，也可能會突然驚醒。
作用機制
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).
安全性與警告
禁忌症
- 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
不良反應
- 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.
藥物相互作用
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).
監測
- 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
藥物動力學
半衰期
吸收
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.
分佈
Highly lipophilic, allowing rapid penetration of the blood-brain barrier to exert central effects.
代謝
Undergoes extensive hepatic biotransformation.
排除
Metabolites are primarily excreted via the kidneys.
過量
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.
可用產品
劑型
- Injection: 1 mg/mL in 10 mL multidose vials
- Injectable: 1 mg/ml solution
獸醫用
- 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
各地核准狀態
Classified as POM-V.
Classified as POM-V.
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儲存與穩定性
Store commercially available injection at room temperature (15-30°C) and protect from freezing.
飼主須知
- 僅限專業使用：本藥物為強效鎮靜劑與麻醉輔助劑，應僅由獸醫專業人員給藥與監測。
- 預期外觀：在鎮靜期間，您寵物的心跳率會顯著下降，牙齦可能顯得蒼白或微藍。這是藥物的預期反應，獸醫團隊會密切監控。
- 保持安靜：即使您的寵物看起來睡得很熟，突然的巨大噪音或粗魯的動作仍可能使牠們驚醒。在牠們恢復期間，請保持環境平靜與安寧。
- 喚醒藥物：在處置結束後，獸醫可能會給予「解藥」（阿替美唑），讓您的寵物能快速且平穩地甦醒。
- 高風險寵物：請確保您的獸醫了解寵物是否有任何既有的心臟、肝臟或腎臟疾病，或者是否懷孕，因為在這些情況下使用此藥物可能不安全。
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