Nitric oxide, also known as nitrogen monoxide, is a molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry. Nitric oxide is a by-product of combustion of substances in the air, as in automobile engines, fossil fuel power plants, and is produced naturally during the electrical discharges of lightning in thunderstorms.

In mammals including humans, NO is an important cellular signaling molecule involved in many physiological and pathological processes. It is a powerful vasodilator with a short half-life of a few seconds in the blood. Long-known pharmaceuticals like nitroglycerine and amyl nitrite were discovered, more than century after their first use in medicine, to be active through the mechanism of being precursors to nitric oxide.

Low levels of nitric oxide production are important in protecting organs such as the liver from ischemic damage. Chronic expression of NO is associated with various carcinomas and inflammatory conditions including Type-1 diabetes, multiple sclerosis, arthritis and ulcerative colitis.^{[citation needed]}

Louis J. Ignarro (born May 31, 1941) is an American pharmacologist. For demonstrating the signaling properties of nitric oxide, he was co-recipient of the 1998 Nobel Prize in Physiology or Medicine with Robert F. Furchgott and Ferid Murad.

Currently, he is professor of pharmacology at the UCLA School of Medicine's department of molecular and medical pharmacology in Los Angeles, which he joined in 1985. Before relocating to California, he was a professor of pharmacology at Tulane University School of Medicine, New Orleans, for 12 years. Ignarro has also previously worked as a staff scientist, research department, for the pharmaceutical division of CIBA-GEIGY Corporation in New York.

Ignarro has published numerous research articles. He received the Basic Research Prize of the American Heart Association in 1998. This was in recognition of his outstanding contributions to the advancement of cardiovascular science. That same year, he was inducted into the National Academy of Sciences and the following year, into the American Academy of Arts and Sciences. Because nitric oxide is indirectly involved in the action of this drug, he is sometimes referred to as the "Father of Viagra".

Ferid Murad (born September 14, 1936) is an Albanian-American physician and pharmacologist, and a co-winner of the 1998 Nobel Prize in Physiology or Medicine. He is also an honorary member of the Academy of Sciences and Arts of Kosovo.

He was born in Whiting, Indiana to Jabir Murat Ejupi, an Albanian from Gostivar, Macedonia, and Henrietta Bowman, an American Christian and raised as a Christian. He received his undergraduate degree in chemistry from the pre-med program at DePauw University in 1958, and MD and pharmacology Ph.D. degrees from Case Western Reserve University in 1965. He was an early graduate of the first explicit MD/PhD program which would later lead to the development of the prestigious Medical Scientist Training Program. He then joined the University of Virginia, where he was made professor in 1970, before moving to Stanford in 1981. Murad left his tenure at Stanford in 1988 for a position at Abbott Laboratories, where he served as a vice president until starting his own biotechnology company, the Molecular Geriatrics Corporation, in 1993. The company experienced financial difficulties, and in 1997 Murad joined the University of Texas to create a new department of integrative biology, pharmacology, and physiology. Here, he was the Professor and Director Emeritus of The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Disease and held the John S. Dunn Distinguished Chair in Physiology and Medicine. In April 2011, he moved to the George Washington University as a Professor in the Department of Biochemistry and Molecular Biology.