Cozaar ® (losartan potassium) is a prescription medication that has been licensed to treat high blood pressure (hypertension) and diabetic nephropathy. It is part of a class of drugs called angiotensin II receptor blockers (ARBs for short). As the name of the drug class implies, Cozaar blocks angiotensin II receptors.n AB rating means that the FDA has determined that a generic medication is equivalent to a brand-name medication. All of the generic losartan versions currently available have an AB rating, meaning they should be equivalent to Cozaar.