- Clonidine and dexmedetomidine are not pure alpha-2 adrenoceptor agonists, but also act at several different receptors
- Specific drug effects depend on the relative selectivity for each receptor type:
Receptor
Location
Effect
Alpha-2
Widespread throughout the brain and periphery
- Primarily sedation and anxiolysis
- Reduce sympathetic outflow resulting in hypotension and bradycardia
Alpha-1
Vascular smooth muscles
- Peripheral vasoconstriction & hypertension
Imidazoline
Autonomic regions of the brain
- Centrally mediated hypotension