Sulfonamide (medicine)
Prontosil, as Bayer named the new drug, was the first medicine ever discovered that could effectively treat a range of bacterial infections inside the body. It had a strong protective action against infections caused by streptococci, and a lesser effect on infections caused by other cocci. However, it had no effect at all in the test tube, exerting its antibacterial action only in live animals. Later, it was discovered that the drug was split into two pieces inside the body, releasing from the inactive dye a smaller, colourless, active compound called sulfanilamide. The discovery dashed the corporation's dreams of enormous profit. The active molecule sulfanilamide (or sulfa) had first been synthesized in 1906 and was widely used in the dye-making industry; its patent had since expired and the drug was available to anyone.