<unk>  is a central alpha-2 adrenergic agonist that is FDA approved for the treatment of hypertension. There is a Black Box Warning for this drug as shown here.  Common adverse reactions include contact dermatitis, erythema, pruritus, xerostomia, dizziness, headache, sedation, somnolence, and fatigue.
Clonidine
Brimonidine 
Phenylephrine 
Metergoline
Clopamide
Methazolamide
Prazosin
Methylergonovine 