Nitric oxide: an environmental pollutant as a therapeutic agent.

There is no effective treatment for patients with pulmonary hypertension because of the lack of a selective pulmonary vasodilator. Recently, nitric oxide (NO) has been found to be the endothelium-derived factor that produces relaxation of the vascular smooth muscle. This discovery has led to the experimental use of inhaled NO as the first selective pulmonary vasodilator. This review summarizes the development of NO inhalation for pulmonary hypertension, including the essential aspects of basic research, which identified NO as a potent endogenous vasodilator. The use of inhaled NO in animal studies of experimental pulmonary hypertension, as well as in the clinical experience so far reported in newborns, children, and adults are summarized. It is concluded that inhaled NO remains experimental and that controlled clinical trials and further studies on potential toxicity are needed before this new therapy can be accepted for routine clinical use.