Merck & Co. is one of the largest pharmaceutical companies established in 1891. It manufactures and markets a broad range of healthcare products for human and animal use. Merck has annual revenue of $27.4 billion and employs over 61,500 people worldwide. Some of Merck's major products include vaccines, prescription drugs, consumer health products, and animal health medicines. One of Merck's prescription drugs is lisinopril, an ACE inhibitor used to treat hypertension, heart failure, and diabetic complications. It has annual global sales of over $1 billion.