Which of the following is an example of an alpha-2 agonist?

• A. Medetomadine
• B. Atropine
• C. Ketamine
• D. Epinephrine

Answer: (A)

An alpha-2 adrenergic agonist acts by activating alpha-2 receptors in the brain and spinal cord, which reduces norepinephrine release and dampens sympathetic outflow. This produces sedation, analgesia, and muscle relaxation, with a characteristic cardiovascular profile that often includes bradycardia and mild peripheral vasoconstriction. Medetomidine fits this profile as a veterinary alpha-2 agonist used as a premed to provide calm sedation and analgesia. Its effects can be reversed with an alpha-2 antagonist such as atipamezole, which helps restore normal activity quickly. The other drugs do not share this mechanism: atropine is an antimuscarinic; ketamine is an NMDA receptor antagonist; epinephrine acts on multiple adrenergic receptors (alpha and beta) rather than selectively alpha-2.