Atipamezole , sold under the brand name Antisedan among others, is a synthetic α2 adrenergic receptor antagonist used for the reversal of the sedative and analgesic effects of dexmedetomidine and medetomidine in dogs.

There is a low rate of side effects, largely due to atipamezole's high specificity for the α2-adrenergic receptor.

[8] Atipamezole is a veterinary drug whose prime purpose is to reverse the effects of the sedative dexmedetomidine (as well as its racemic mixture, medetomidine).

[9][12][13] Atipamezole is licensed in the United States for intramuscular injection (IM) in dogs; it is, however, used off-label in cats, rabbits,[14] and farm animals such as horses and cows,[12] as well as in zoo medicine for reptiles (including tortoises, turtles, and alligators), armadillos, hippopotamuses, giraffes, okapi, and others.

[24] While there are no absolute contraindications to atipamezole, it is recommended against being given with anticholinergics, as both can cause dramatic increases in heart rate.

It can potentially cause CNS excitement, which can lead to tremors, tachycardia (increased heart rate), and vasodilation.

The vasodilation leads to a transient decrease in blood pressure, which (in dogs) increases to normal within 10 minutes.

[12] There is a possibility of the sedation reversing abruptly, leading to nervous, aggressive, or delirious dogs.

This is thought to be combination of sudden hypotension added onto the low heart rate caused by sedatives.

It does not directly interact with dexmedetomidine;[34] rather, their structural similarity allows atipamezole to easily compete for receptor binding sites.

[31] Atipamezole has a rapid onset: it reverses the decreased heart rate caused by sedation within three minutes.

[27] Because atipamezole increases sexual activity in monkeys, there have been claims of its potential to treat erectile dysfunction.