羅米非定
羅米非定（Romifidine）是一種強效的**α2-腎上腺素受體激動劑**，在獸醫學中主要用作鎮靜劑、肌肉鬆弛劑和鎮痛藥。 主要臨床特點包括： * **馬匹應用**：在馬匹臨床中極受歡迎，因為在常用的α2-激動劑（如賽拉嗪或右美托咪定）中，它能提供**最長的鎮靜時間**，且在鎮靜劑量下通常引起的**共濟失調較輕**，使馬匹在站立處置期間能保持更穩定的站姿。 * **小動物應用**：雖然在美國僅獲FDA批准用於馬匹，但在部分歐洲國家，它被批准並用於犬貓，作為可靠的麻醉前給藥和鎮靜劑。 * **鎮痛與鎮靜對比**：與大多數α2-激動劑一樣，其鎮痛作用的持續時間明顯短於肉眼可見的鎮靜時間。 > **臨床要點**：儘管動物（尤其是馬匹）看起來已深度鎮靜，但仍可能對聽覺或觸覺刺激做出突然且劇烈的反應。請務必保持安全的操作規範。
作用機制: Romifidine exerts its effects by binding to and stimulating **alpha-2 adrenergic receptors** located in the central and peripheral nervous systems. * **Central Nervous System (CNS)**: Presynaptic alpha-2 activation causes feedback inhibition of **norepinephrine** release → resulting in dose-dependent sedation, muscle relaxation, and analgesia. It also reduces overall sympathetic outflow. * **Cardiovascular System**: Postsynaptic alpha-2 activation in peripheral vascular smooth muscle → initial **vasoconstriction** and transient hypertension → triggers a secondary vagal reflex → **bradycardia** and subsequent hypotension. * **Metabolic & GI**: Inhibits insulin release from pancreatic beta cells → transient **hyperglycemia**. It also decreases gastrointestinal motility and alters thermoregulatory mechanisms.
各物種劑量
- For sedation · 200-400 micrograms/kg IV or IM · IV/IM · Single dose · IM gives sedation in ~10 mins, persists ~60 mins. IV onset ~5 mins. Atipamezole (400 mcg/kg IM) reverses 400 mcg/kg romifidine.
- As a preanesthetic · 200 micrograms/kg IM 10-15 minutes prior to giving ketamine at 10 mg/kg IM · IM · Single dose · Provides surgical anesthesia for up to 30 mins. 400 mcg/kg extends period. Top-up dose of 50% initial doses can prolong anesthesia.
- As an analgesic adjunct · 20-40 micrograms/kg IM, IV · IM/IV · Single dose · May combine with an anticholinergic agent in exercise-tolerant patients free from heart disease.
- For epidural anesthesia for paralumbar analgesia or laparotomy · Romifidine 50 micrograms/kg plus morphine 0.1 mg/kg · Epidural · Single dose · 12 hours maximum · Extra-label use. Contact FARAD for withdrawal times.
- For sedation and analgesia · 40-120 micrograms/kg IV slowly one time · IV · Single dose · Onset 30 sec to 5 mins, subsides over 2-4 hours. Duration of analgesia is shorter than sedation.
- As a preanesthetic · 100 micrograms/kg as slow, single IV injection · IV · Single dose · Induce anesthesia after maximal sedation is achieved (2-4 mins). Decrease anesthetic doses due to sparing effects.
- For sedation · 40-120 micrograms/kg IV, IM or SQ · IV/IM/SQ · Single dose · IV causes sedation in ~5 mins. SC/IM delayed to ~30 mins and depth is lower. Atipamezole (200 mcg/kg IM) reverses 120 mcg/kg romifidine.
給藥途徑
禁忌症
- Known hypersensitivity to romifidine
- Concurrent use with intravenous potentiated sulfonamides
- Preexisting cardiac conditions, arrhythmias, or severe cardiovascular compromise
- Severe respiratory, hepatic, or renal disease
- Pregnancy (especially last month in horses, and throughout pregnancy in dogs/cats)
- Shock or severe systemic debilitation
不良反應
- Bradycardia (can be profound)
- First- and second-degree atrioventricular (AV) heart block
- Sinus arrhythmias
- Initial hypertension followed by hypotension
- Ataxia and muscle tremors
- Sweating and piloerection (horses)
- Vomiting (especially common in cats)
- Transient hyperglycemia
- Decreased gastrointestinal motility (flatulence, mild colic in horses)
- Increased urination
- Altered thermoregulation (hypothermia or hyperthermia)
- Swelling of face, lips, and upper airways; stridor (horses)
- Paradoxical excitation (rare)
藥物相互作用
- Intravenous Potentiated Sulfonamides (e.g., trimethoprim/sulfa) · May cause fatal dysrhythmias; concurrent use is strictly contraindicated.
- Other Alpha-2 Agonists (e.g., xylazine, dexmedetomidine) & Epinephrine · Additive cardiovascular and CNS effects; epinephrine may potentiate adverse effects and arrhythmias.
- Phenothiazines (e.g., acepromazine) · Can result in severe, compounding hypotension.
- Anesthetics, Opiates, Sedatives/Hypnotics · Synergistic CNS depression; significantly reduces the required dose of induction and maintenance anesthetics. Increased risk of arrhythmias with thiopental, ketamine, or halothane.
監測
- Level of sedation and analgesia
- Respiratory rate and effort
- Heart rate and rhythm (ECG recommended during anesthesia)
- Blood pressure (especially during general anesthesia)
- Body temperature (monitor for hypothermia during prolonged procedures)
過量
In **horses**, experimental doses up to 5X (600 mcg/kg) caused sinus bradycardia, 2nd-degree heart block, occasional apnea, mild respiratory stridor, deep sedation, frequent urination, and sweating. No clinically significant alterations in blood gases or chemistries were noted. In **dogs**, doses up to 10X (1 mg/kg IV daily for 4 weeks) resulted in no serious adverse effects reported. **Treatment**: If necessary, an alpha-2 antagonist such as **atipamezole** (30-80 mcg/kg) or **yohimbine** can be administered to rapidly reverse the sedation and cardiovascular adverse effects.
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