The invention provides methods for treating disorders associated with selective subtype modulation of alpha 2 adrenergic receptors. In particular, the invention provides methods employing well-defined N-[1-(2 and/or 3-substituted-phenyl)-alkyl]-(4,5-dihydro-1H-imidazol-2-yl)-amines and pharmaceutical compositions thereof to treat disorders associated with selective subtype alpha 2 adrenergic receptor modulation.