Detomidine
> **Detomidine** is a potent alpha-2 adrenergic agonist used primarily in equine medicine for its profound sedative and analgesic properties. * **Potency:** It is approximately 50 to 100 times more potent than xylazine. * **Clinical Use:** Widely used for standing sedation, minor surgical procedures, and analgesia (especially for colic) in horses. It has also been used off-label in cattle, small ruminants, camelids, and birds. * **Important Caveat:** Even when horses appear deeply sedated, they may still respond suddenly to external stimuli (e.g., kicking). The addition of an opioid (like butorphanol) can help temper this startle response and improve the quality of sedation.
Mechanism: Detomidine acts as a potent and highly specific agonist at **alpha-2 adrenergic receptors** in the central and peripheral nervous systems. * **Sedation & Analgesia:** Activation of presynaptic alpha-2 receptors in the locus coeruleus and dorsal horn of the spinal cord โ inhibition of norepinephrine release โ decreased sympathetic outflow, resulting in profound sedation, muscle relaxation, and analgesia. * **Cardiovascular Effects:** Initial activation of peripheral postsynaptic alpha-2 receptors โ transient vasoconstriction and **hypertension** โ compensatory vagal reflex โ profound **bradycardia** and potential AV block. Central sympatholytic effects then lead to a prolonged decrease in blood pressure.
Dosing by species
- Anesthesia ยท 0.01 mg/kg IM ยท IM ยท once ยท Followed by propofol at 3-5 mg/kg IV.
- Analgesia ยท 0.005-0.05 mg/kg IV or IM q3-6 hours (once) ยท IV/IM ยท q3-6h ยท once
- Anesthesia ยท 0.01 mg/kg IM ยท IM ยท once ยท Followed by propofol at 3-5 mg/kg IV.
- Analgesia ยท 0.005-0.05 mg/kg IV or IM q3-6 hours (once) ยท IV/IM ยท q3-6h ยท once
- Sedation/analgesia ยท 30-60 micrograms/kg (0.03-0.06 mg/kg) IV or IM ยท IV/IM ยท once ยท Not FDA-approved.
- Analgesia ยท 0.01 mg/kg IV ยท IV ยท once ยท 1/2 hour ยท Withdrawal times: Milk = 72 hours; Slaughter = 7 days.
- Sedation/analgesia ยท 20-40 micrograms/kg (0.02-0.04 mg/kg) IV or IM ยท IV/IM ยท once ยท IV only for analgesia. Lower dose provides 30-90 min sedation/30-45 min analgesia. Higher dose provides 90-120 min sedation/45-75 min analgesia.
- Sedation/analgesia (Sublingual Gel) ยท 0.04 mg/kg (0.018 mg/lb) (0.040 mg/kg) placed beneath the tongue ยท Sublingual ยท once ยท Not meant to be swallowed.
- Marked abdominal pain (not surgical candidates or long transport) ยท 0.01-0.02 mg/kg (10-20 micrograms/kg) IV or IM ยท IV/IM ยท once
Routes of administration
Contraindications
- Preexisting AV or SA heart block
- Severe coronary insufficiency
- Cerebrovascular disease
- Severe respiratory disease
- Chronic renal failure
Adverse effects
- Initial blood pressure increase (hypertension)
- Profound bradycardia and heart block (AV block)
- Piloerection
- Sweating
- Ataxia
- Salivation
- Slight muscle tremors
- Penile prolapse
- Decreased gastrointestinal motility
Drug interactions
- Other Alpha-2 Agonists (e.g., xylazine, medetomidine, clonidine) ยท Not recommended to be used together as effects may be additive.
- Anesthetics, Opiates, Sedative/Hypnotics ยท Effects may be additive; dosage reduction required. Increased risk for arrhythmias with thiopental, ketamine, or halothane.
- Epinephrine ยท Do not use to treat cardiac effects caused by detomidine, as epinephrine possesses alpha agonist effects.
- Phenothiazines (e.g., acepromazine) ยท Severe hypotension can result.
- Potentiated Sulfonamides (e.g., trimethoprim/sulfa) ยท Fatal dysrhythmias may occur if used with intravenous potentiated sulfonamides.
Monitoring
- Level of sedation and analgesia
- Cardiac rate and rhythm
- Blood pressure (if indicated)
Overdose
> **Toxicity Profile:** * Tolerated by horses at 5X the high dose level (0.2 mg/kg). * Doses of 10-40X recommended can cause severe respiratory and cardiovascular changes that can become irreversible and cause death. * **Reversal:** Alpha-2 antagonists such as **atipamezole** (50-100 micrograms/kg) or **yohimbine** can be successfully used to reverse some or all effects of inadvertent overdoses.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.