Romifidine
2-(2-Bromo-7-fluoroanilino-)-2-imidazoline
Also known as: Sedivet · Romidys · Sedivan · STH-2130 · romifidiini · romifidina · romifidinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidencePostanesthesia sedation (extra-label)
Verified clinician required
- once
NA
Governing clinical context (1)
- Store romifidine HCl injection at controlled room temperature (15°C to 30°C [59°F-86°F]).
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Romifidine is a potent alpha-2 adrenergic agonist utilized primarily in veterinary medicine for its profound sedative, muscle relaxant, and analgesic properties.
Key clinical highlights include:
- Equine Practice: It is highly favored in horses because it provides the longest duration of sedation among commonly used alpha-2 agonists (like xylazine or detomidine) and typically causes less ataxia at sedative doses, allowing horses to remain more firmly planted during standing procedures.
- Small Animal Use: While FDA-approved only for horses in the US, it is approved and utilized in dogs and cats in several European countries as a reliable preanesthetic and sedative.
- Analgesia vs. Sedation: As with most alpha-2 agonists, the duration of analgesia is significantly shorter than the duration of visible sedation.
Clinical Pearl: Despite appearing deeply sedated, animals (especially horses) can still react suddenly and violently to auditory or tactile stimuli. Always maintain safe handling practices.
Mechanism of action
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.
Safety & warnings
Contraindications
- 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
Adverse effects
- 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)
Precautions
Important Warnings:
- Sudden Arousal: Animals may appear deeply sedated but can still respond aggressively (e.g., kicking) to external stimuli. Use appropriate physical restraint.
- Cardiovascular Depression: Causes significant bradycardia and AV block. Use with extreme caution in patients with preexisting heart disease.
- Vomiting Risk: Dogs and particularly cats may vomit after administration. Fasting for at least 12 hours prior to use is recommended in small animals.
- Thermoregulation: Can cause hypothermia during prolonged sedation; provide thermal support.
- Human Safety: Can be absorbed through the skin and oral mucosa. Handlers should avoid self-exposure and wash immediately if accidental contact occurs.
Drug interactions
May cause fatal dysrhythmias; concurrent use is strictly contraindicated.
Additive cardiovascular and CNS effects; epinephrine may potentiate adverse effects and arrhythmias.
Can result in severe, compounding hypotension.
Synergistic CNS depression; significantly reduces the required dose of induction and maintenance anesthetics. Increased risk of arrhythmias with thiopental, ketamine, or halothane.
Monitoring
- 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)
Pharmacokinetics
Half-life
Absorption
Dogs/Cats: Bioavailability after IM is 86% (dogs) and 95% (cats). SC bioavailability in dogs is 92%. Peak levels after IM occur in ~50 mins (dogs) and ~25 mins (cats).
Distribution
Horses: Vd ~2-3 L/kg. Dogs: Vd ~3 L/kg. Cats: Vd ~6 L/kg.
Metabolism
Biotransformed in the liver.
Elimination
Dogs: ~80% eliminated in urine, 20% in feces. Horses: Clearance ~100 mL/min/kg.
Overdose
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.
Available products
Formulations
- Injection: 10 mg/mL (1%)
- Injection: 1 mg/mL (0.1%)
Veterinary
- Romifidine HCl 1% (10 mg/mL) Injection (Sedivet)
- Romifidine HCl 0.1% (1 mg/mL) Injection (Romidys - Europe)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at controlled room temperature (15-30°C).
Client information
- Professional Use Only: This medication is strictly administered by veterinary professionals in a clinical setting.
- Caution Around Sedated Horses: If you are assisting with or handling a horse that has received romifidine, exercise extreme caution. Even if the horse appears deeply asleep or heavily sedated, it can still react suddenly and defensively (e.g., kicking or striking) if startled by loud noises or sudden touch.
- Fasting for Pets: If your dog or cat is scheduled to receive this medication, your veterinarian will likely recommend withholding food for at least 12 hours beforehand, as the drug frequently causes nausea and vomiting shortly after administration.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.