Clonidine-d4 Hydrochloride is a deuterated compound of Clonidine Hydrochloride. Clonidine Hydrochloride has a CAS number of 4205-91-8. Clonidine is a centrally active alpha-adrenergic agonist used predominantly as an antihypertensive agent, usually in combination with other agents. Despite wide scale use for many years, clonidine has not been linked definitively to either serum aminotransferase elevations or clinically apparent liver injury.