[Nitric oxide: a different kind of gas]

Nitric oxide (NO), the first gas to obtain temporary approval for use in medicine, is regulated in private and public health care facilities by the supply, prescription and dispensing rules applied for drugs with special modalities controlling its administration. This apparently simple gas which diffuses easily from one cell to another is actually very complex in its form and reactivity, making it an unconventional messenger. The life time of a molecule is very short. NO is synthesized and released continuously. Its direct or mediated vasodilator effect has led to four temporary approval rulings validated again in 1997 by the national health authorities.