Sedation of a healthy animal with dexmedetomidine and an opioid
One IM injection, both drugs in one syringe; reversible sedation for examination, radiography or a short, mildly painful procedure in a healthy animal, including a fractious one. Not enough for surgery.1,2
This page is an educational reference for veterinarians and veterinary students. It does not replace a thorough examination, clinical judgment, or the attending veterinarian's final decision. Doses are for adult animals, per kilogram; the amount and volume of each drug for a patient, and the doses for neonates and seniors, are calculated in the tool itself.
Step by step
per kilogram of body weight
1 Preanesthetic preparation Before the injection
Healthy animal: allow free access to water; withhold food for 4–6 hours before anesthesia.3
Animal under 8 weeks or under 2 kg: withhold food for no more than 1–2 hours, monitor blood glucose before, during and after induction, and schedule it as the first patient of the day.3
Animal with a history or risk of regurgitation: withhold food and water for 6–12 hours.3
Vomiting is common with dexmedetomidine; pretreatment with an antiemetic such as maropitant reduces it.3,4
This combination only sedates and is not enough for surgery or intubation. If sedation is not enough, do not inject dexmedetomidine again; complete the anesthesia with an IV induction agent.2,4,5
Give it with the opioid in the same syringe, as a single IM injection.1
This range is for moderate sedation, and it stays the same with an opioid.1,5
Give a nervous, aggressive or excited animal time to settle before the injection.2
Effects of this drug
Produces sedation and analgesia; their depth and duration depend on the dose.2,4
Used with an opioid: this combination is common for sedation for noninvasive procedures.1,6
Lowers heart rate and cardiac output and constricts peripheral vessels; mucous membranes may look pale or bluish even though arterial oxygenation is normal.2,4
Vomiting is common, usually 5–10 minutes after injection; more common in cats and at higher doses.2,4
Its effects, including analgesia, are reversed by atipamezole.1,7
3 Sedation With dexmedetomidine, in the same syringe
After IM injection, its effect begins within 10–20 minutes and lasts 2–4 hours.5
Does not release histamine and causes little or no vomiting.1,5
Like morphine, it may slow the heart rate and depress breathing.5
On its own it may cause restlessness in a young, healthy animal; it is given with a sedative.1
4 Onset From the injection
Watch the animal closely in a quiet place; sedation needs monitoring and support just as anesthesia does. Monitor breathing, heart rate and mucous membrane color.5
Give oxygen by mask to a deeply sedated animal; airway control may become necessary, so have intubation equipment ready.5
Methadone and morphine start to work 10–20 minutes after IM injection; buprenorphine after 20–45 minutes.5
An animal that is very aroused before the injection may not sedate well.6
5 Sedation 30–90 minutes
Sedation with this combination lasts about 30–90 minutes.1
If sedation is not enough for the procedure or the procedure is painful, do not inject dexmedetomidine again; complete the anesthesia with an IV induction agent, slowly, to effect.1,2,5
6 Recovery and reversal After the procedure
Continue monitoring and supporting the animal until full recovery.5
Keep the animal warm; give no food or water until it can swallow.2
Both drugs are reversible: dexmedetomidine is reversed by atipamezole, and methadone and morphine by naloxone; their amounts and volumes are in the reversal drugs box.1,7
Reversal also removes the analgesia; if the procedure was painful, treat the pain separately.6
The percentage on each side is not a measurement but a qualitative grade from the sources: full 100, good 75, partial 50, low 25, none zero. It refers to the peak effect after the injection, not the whole duration.
HypnosisLoss of consciousness — 0% (None)
This protocol sedates rather than anesthetizes: it gives moderate sedation, and the procedure is done without the animal losing consciousness.4,5
If anesthesia is needed, an IV induction agent is added.1
An opioid with an alpha-2 agonist deepens sedation but does not produce anesthesia.4,6
AnalgesiaPain control — 75% (Good)
Dexmedetomidine provides analgesia, but it is supportive and shorter than its sedation.6
The opioid provides the main analgesia, and dexmedetomidine enhances it.1,6
For a painful procedure, also use local anesthesia wherever possible.5
Muscle relaxationRelaxed muscle tone — 50% (Partial)
Alpha-2 agonists produce muscle relaxation; the animal is calm but not anesthetized.6
Blood pressure: First high, then normal or low
Dexmedetomidine raises blood pressure first, then brings it back to normal or below, and slows the heart rate; the opioid may also slow the heart rate.2,5
Dexmedetomidine ↑↓ Rises, then falls: Raises blood pressure first, then brings it back to normal or below; slows the heart rate.2
Before you start: contraindications
Contraindication Do not give dexmedetomidine in: cardiovascular disease, severe systemic disease, moribund animals, or hypersensitivity to the drug.2
Cautions and notes
Caution This combination only sedates: it is for examination, radiography and noninvasive procedures with mild to moderate pain, not for surgery or intubation; those need anesthesia.2,4
Caution This protocol is for healthy animals. In sick or debilitated animals, give dexmedetomidine only after weighing the risks and benefits.2
Caution Dexmedetomidine slows the heart and may make its rhythm irregular; the opioid also slows the heart rate. Monitor heart rate and rhythm.1,2,6
Caution Do not give atropine or another anticholinergic with dexmedetomidine unless bradycardia and hypotension occur together; blood pressure may rise very high.2,4,6
Caution Give dexmedetomidine with caution in diabetes, liver or kidney disease, low or high blood pressure, and after trauma.6
Caution The opioid may depress breathing and slow the heart rate; monitor breathing and heart rate and have oxygen ready.5
Caution Monitor body temperature and keep the animal warm during anesthesia and recovery.2
Caution Do not inject dexmedetomidine again; for a longer procedure, maintain anesthesia with an inhalant.1,2
Caution Dexmedetomidine is not recommended during pregnancy and lactation.2
Note This combination is also used to calm fractious or aggressive animals.1
Note Dexmedetomidine and the opioid can be drawn up in one syringe.1
If needed, give it IM at the end of the procedure, or if the effects of dexmedetomidine become life-threatening. The sedation, analgesia and cardiorespiratory effects of dexmedetomidine are reversed, and the animal usually wakes and stands within 15 minutes.2,7
If the procedure was painful, treat the pain separately, because the analgesia of dexmedetomidine is reversed too. After the injection, leave the animal in a quiet place; in dogs, transient hypotension has been seen in the first 10 minutes.6,7
The lowest amount is for partial reversal and the highest for full reversal. As the opioid is reversed, its analgesia also decreases or disappears; reassess pain.1,4