An anticoagulant drug to prevent formation of blood clots in blood vessels. Tirofiban (Aggrastat) works by interfering with the process by which blood clots, chiefly by inhibiting the clumping of platelets. In combination with heparin, tirofiban is given as an injection both before and after open heart surgery to prevent the formation of clots in blood vessels. It is also used to treat acute coronary syndrome, which is acute blood flow blockage in the heart.