Atipamezole is a selective alpha2-adrenergic antagonist used to reverse the effects of alpha2-agonist sedatives. Its main veterinary application is reversal of medetomidine or dexmedetomidine in dogs, with additional species-specific and extra-label uses. It also has a role in selected intoxications that produce clinically important alpha2-mediated effects.
Atipamezole competitively blocks alpha2-adrenoceptors and removes agonist-induced inhibition of norepinephrine release. Restoration of noradrenergic signaling promotes arousal and reverses alpha2-mediated sedation, analgesia and autonomic changes. The degree of reversal depends on receptor occupancy, the agonist involved and concurrent drugs. In amitraz intoxication, antagonism addresses the alpha2 activity of amitraz and its metabolites.
Reassess for recurrence because amitraz may outlast the antagonist.
Medetomidine reversal
Reference only
IM
For 5 mg/mL atipamezole and 1 mg/mL medetomidine, the source describes equal IM volumes. Prior agonist dose determines antagonist amount; retain the concentration-specific ratio.
Cats
Use / stage
Dose
Route
Schedule
Instructions
Dexmedetomidine reversal
0.2 mg/kg
IM, IV
Once
Medetomidine reversal
Reference only
IM
For 5 mg/mL atipamezole and 1 mg/mL medetomidine, the source describes equal IM volumes. Prior agonist dose determines antagonist amount; retain the concentration-specific ratio.
Rabbits
Use / stage
Dose
Route
Schedule
Instructions
Medetomidine reversal
0.5 mg/kg
IM, SC
Once
Medetomidine reversal
0.25 mg/kg
IV
Once
Mice
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.1–1 mg/kg
IM, IP, IV, SC
Once
Rats
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.1–1 mg/kg
IM, IP, IV, SC
Once
Gerbils
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.1–1 mg/kg
IM, IP, IV, SC
Once
Hamsters
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.1–1 mg/kg
IM, IP, IV, SC
Once
Guinea pigs
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.1–1 mg/kg
IM, IP, IV, SC
Once
Cattle
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.02–0.1 mg/kg
IV
Once
Titrate to effect.
Sheep
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.02–0.1 mg/kg
IV
Once
Titrate to effect.
Alpha-2 agonist reversal – alternative
0.1–0.2 mg/kg
IV, IM
Once
If IV, give slowly; observe the delay after dissociative combinations.
Goats
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.02–0.1 mg/kg
IV
Once
Titrate to effect.
Alpha-2 agonist reversal – alternative
0.1–0.2 mg/kg
IV, IM
Once
If IV, give slowly; observe the delay after dissociative combinations.
Llamas
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.02–0.1 mg/kg
IV
Once
Titrate to effect.
Alpha-2 agonist reversal – alternative
0.1–0.2 mg/kg
IV, IM
Once
If IV, give slowly; observe the delay after dissociative combinations.
Alpacas
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.02–0.1 mg/kg
IV
Once
Titrate to effect.
Alpha-2 agonist reversal – alternative
0.1–0.2 mg/kg
IV, IM
Once
If IV, give slowly; observe the delay after dissociative combinations.
Birds
Use / stage
Dose
Route
Schedule
Instructions
Alpha-2 agonist reversal
0.5 mg/kg
IM
Once
Reptiles
Use / stage
Dose
Route
Schedule
Instructions
Medetomidine reversal
Reference only
IM
Atipamezole amount 4-5 times the medetomidine dose in the ketamine/medetomidine protocol; reversal may take up to one hour. Do not give IV.
Provide alternative analgesia before reversing a painful patient. Protect recovering animals from falls and observe for resedation.
After ketamine/tiletamine combinations in small ruminants or camelids, do not reverse too early: allow at least 30, preferably 60, minutes for the dissociative component to diminish.
The equal-volume rule applies only to the specified agonist and antagonist concentrations; it is not a universal volume rule.
