Amyl nitrite was discovered in 1844 and was found to relax the tiny blood vessels known as capillaries that connect arteries and veins. In 1867, Thomas Lauder Brunton, a medical student in Scotland, found the drug helped relieve angina by increasing blood flow to the heart. A few years later, nitroglycerine was found to have a similar dilating effect. Although both can still be prescribed for angina, nitroglycerine is much more commonly prescribed because it is more easily administered and has fewer side effects. A prescription was required for amyl nitrite until the early 1960s when the FDA approved it for over-the-counter sale. That approval was withdrawn in 1969 when the FDA found the chemical was being used as a recreational drug.