Benicar (Olmesartan) is an angiotensin receptor blocker (ARB). It blocks a chemical that tightens blood vessels. This makes blood vessels relax, which lowers blood pressure and allows more blood and oxygen to get to your heart and other organs. Cozaar (Losartan) is an angiotensin receptor blocker (ARB). It blocks a chemical that tightens blood vessels. This makes blood vessels relax, which lowers blood pressure and allows more blood and oxygen to get to your heart and other organs. Type of medication.