AR and muscle cramp: α2-AR, on which dexmedetomidine acts, is a unique AR that negatively controls neural transmission, which makes it useful target of drugs for a broad range of conditions, e.g., hypertension (methyldopa hydrate, clonidine hydrochloride), glaucoma (brimonidine tartrate), spasm, multiple sclerosis/MS, muscular atrophic lateral sclerosis/ALS (tizanidine hydrochloride) and attention defect hyperactivity disorder/ADHD (guanfacine hydrochloride, clonidine hydrochloride) treatment.