Amrinone is a 3,4'-bipyridine substituted at positions 5 and 6 by an amino group and a keto function respectively. A pyridine phosphodiesterase 3 inhibitor, it is a drug that may improve the prognosis in patients with congestive heart failure. It has a role as an EC 3.1.4.* (phosphoric diester hydrolase) inhibitor and a cardiovascular drug.