Sodium nitroprusside is primarily used as a vasodilator. It was first used in human medicine in 1928.[4] By 1955, data on its safety during short-term use in patients with severe hypertension had become available.[4] Despite this, due to difficulties in its chemical preparation, it was not finally approved by the US FDA until 1974 for the treatment of severe hypertension.[4] By 1993, its popularity had grown such that total sales in the US had totalled US$2 million.[4]