OLMESARTAN MEDOXOMIL), A PRODRUG, IS HYDROLYZED TO OLMESARTAN DURING ABSORPTION FROM THE GASTROINTESTINAL TRACT. OLMESARTAN IS A SELECTIVE AT 1 SUBTYPE ANGIOTENSIN II RECEPTOR ANTAGONIST. OLMESARTAN BLOCKS THE VASOCONSTRICTOR EFFECTS OF ANGIOTENSIN II BY SELECTIVELY BLOCKING THE BINDING OF ANGIOTENSIN II TO THE AT 1 RECEPTOR IN VASCULAR SMOOTH MUSCLE. OLMESARTAN HAS MORE THAN A 12,500-FOLD GREATER AFFINITY FOR THE AT 1 RECEPTOR THAN FOR THE AT 2 RECEPTOR.