右美托咪啶
右美托咪啶是一種強效且高度特異性的**Alpha-2 腎上腺素受體激動劑**，在獸醫學中主要用作鎮靜劑、鎮痛劑和麻醉前導藥。它是美托咪啶的右旋對映異構體，效力約為消旋混合物的兩倍。
作用機制: Dexmedetomidine acts as a highly selective agonist at **pre-synaptic alpha-2 adrenergic receptors** in the central and peripheral nervous systems. * **CNS Effects:** Activation of alpha-2 receptors in the locus coeruleus → decreased norepinephrine release → profound sedation, anxiolysis, and analgesia. * **Cardiovascular Effects:** Activation of peripheral post-synaptic alpha-2B receptors in vascular smooth muscle → intense vasoconstriction → increased systemic vascular resistance (SVR) → reflex bradycardia mediated by baroreceptors. Central alpha-2A activation subsequently decreases sympathetic outflow. * **Other Effects:** Decreases GI secretions, alters intestinal motility, induces diuresis (via inhibition of ADH), and causes mild muscle relaxation.
各物種劑量
- Sedation and analgesia · 40 micrograms/kg IM · IM · Single dose · Fasted for 12 hours prior. Apply eye lubricant. Peak effects at 30 minutes.
- Sedation and analgesia · 375 micrograms/m2 body surface area (BSA) IV; 500 micrograms/m2 BSA IM · IV/IM · Single dose · Microgram/kg dosage decreases as body weight increases. Fast for 12 hours prior. Peak effects at 30 minutes.
- Preanesthetic · 125-375 micrograms/m2 IM · IM · Single dose · Accurate dosing not possible < 2 kg.
- Premed prior to propofol or face mask induction (geriatric/renal/liver dysfunction) · 62.5 micrograms/m2 · IM/IV · Single dose · Combine with equal volumes of opioid and ketamine.
- Slightly heavier sedation for radiographic procedures (ASA II or III) · 125 micrograms/m2 · IM/IV · Single dose · Combine with equal volumes of opioid and ketamine.
- Minor surgery, Penn hip or OFA-types of radiographic procedures · 250 micrograms/m2 · IM/IV · Single dose · Combine with equal volumes of opioid and ketamine.
- Surgical plane of anesthesia for OHE, castration, or abdominal surgery · 375 micrograms/m2 · IM/IV · Single dose · Combine with equal volumes of opioid and ketamine. Lateral recumbency in 5-8 minutes.
- Immobilizing extremely fractious dogs and wolf-hybrid dogs · 500 micrograms/m2 · IM · Single dose · Combine with equal volumes of opioid and ketamine. Rarely required.
- Post-operative pain management in critically ill dogs · Loading dose of 25 micrograms/m2 IV, followed by a constant rate infusion for 24 hours at 25 micrograms/m2/hr · IV · CRI · 24 hours · Morphine rescue analgesia may be required.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Cardiovascular disease
- Respiratory disorders
- Liver or kidney diseases
- Shock or severe debilitation
- Stress due to extreme heat, cold, or fatigue
- Puppies < 16 weeks (US label) or < 6 months (UK label)
- Kittens < 12 weeks (US label) or < 5 months (UK label)
- Hypersensitivity to the active substance
不良反應
- Bradycardia (profound)
- Occasional AV blocks
- Decreased respiration / Apnea
- Hypothermia
- Urination
- Vomiting
- Hyperglycemia
- Pain on injection (IM)
- Prolonged sedation
- Paradoxical excitation
- Hypersensitivity
- Pulmonary edema
- Death from circulatory failure (rare)
- Muscle tremors
- Transient hypertension
- Reduced tear production
藥物相互作用
- Anesthetics, Opiates, Sedative/Hypnotics · Effects may be additive; dosage reduction of one or both agents may be required. General anesthetic requirements may be reduced between 30-60%.
- Atropine, Glycopyrrolate · Can significantly increase arterial blood pressure and heart rate; use together is not recommended in dogs due to increased cardiac workload.
- Epinephrine · Possesses alpha agonist effects; do not use to treat cardiac effects caused by dexmedetomidine.
- Yohimbine · May reverse the effects, but atipamezole is preferred for clinical use.
監測
- Level of sedation and analgesia
- Heart rate and rhythm
- Blood pressure
- Respiration rate and pulse oximetry
- Body temperature (monitor for hypothermia)
過量
Single doses of up to 5X (IV) and 10X (IM) were tolerated in dogs, but adverse effects (heart block, PVCs, tachycardia, profound sedation) can occur. > **Important:** Treatment of dexmedetomidine-induced bradycardia with anticholinergic agents (atropine or glycopyrrolate) is usually **not recommended** due to the risk of severe hypertension and arrhythmias. **Atipamezole** is the safest and most effective choice to reverse any dexmedetomidine-induced effects or overdose.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。