Table 1. Major differences in the pharmacology of clonidine and dexmedetomidine.

Clonidine	Dexmedetomidine*
Developed in the 1960s	Developed in the 1980s
Clinical practice: originally prescribed as a antihypertensive then as an analgesic in chronic pain (1983)	Clinical practice: tested in volunteers (1991) then used as a sedative in ICU (1999)
Ratio α2:α1 receptor binding is 200:1	Ratio α2:α1 receptor binding is 1600:1
Octanol/buffer partition coefficient: 0.8	Octanol/buffer partition coefficient: 2.8 More lipophilic (3.5-fold) than clonidine
Plasmatic half-life T½: 9-12 hours	Plasmatic half-life T½: 2-2.5 hours
Protein binding: 50%	Protein binding: 94%

*Detomidine, the racemic mixture, is widely used in veterinary medicine; dexmedetomidine is the active isomer of medetomidine. ICU, intensive care unit.