Glyceryl Trinitrate , which was originally synthesized by Ascanio Sobrero, was used by Alfred Nobel to manufacture dynamite. Its antianginal effect was first discovered in late 1860s with two interesting observation made from workers in Nobel's dynamite factories. First, factory workers on Monday mornings often complained of headaches that disappeared over the weekends. Second, factory workers suffering from angina pectoris or heart failure often experienced relief from chest pain during the work week, but which reoccurred on weekends. Both effects were attributed to the vasodilator action of Glyceryl Trinitrate and the use of Glyceryl Trinitrate in medical treatment was started to be investigated.