Arsphenamine

Arsphenamine is a pharmaceutical based on organic molecules containing arsenic. It was developed in the 1910s and became the first effective treatment against syphilis. It later became the first pharmaceutical used in chemotherapy. In modern medicine, it is primary used against African trypansomiasis.
Arsphenamine breaks down when exposed to air, and could not be administered as a tablet. As such, it had to be dissolved in distilled water with as little exposure to air as possible during the process. A more stable version was introduced in 1912, but it was less effective. In either case, the drug had to be stored in a nitrogen environment to prevent spoilage. 
Arsphenamine at WikipediaCategory:Pharmaceuticals