How safe is nitric oxide?

Nitric oxide: Nitric oxide supplemets are orovided by l-arginine , which in pharnaceutical grade should be taken on a emty stomach and in large doses.Some peo;ple cannot tolerate that dosage, but by far it is not known to be harmful.

Nitrous oxide?: I think you meant nitrous oxide. Long term exposure can cause vitamin B12 deficiency, neurologic consequences and reproductive side effects (in pregnant females). Fyi Nitric Oxide is a potent vasodilator.