Clonidine is in a class of medications called centrally acting alpha-agonist hypotensive agents. Clonidine treats high blood pressure by decreasing your heart rate and relaxing the blood vessels so that blood can flow more easily through the body. Catapres (clonidine hydrochloride) and Xanax (alprazolam) are used to treat anxiety. Catapres is mainly used to treat high blood pressure (hypertension). Xanax is also used to treat panic attacks.