Prontosil was the first successful synthetic antibacterial drug used widely against bacterial infections.
Gerhard Domagk and his research team discovered Prontosil’s antibacterial effect in the 1930s. The red dye protected laboratory animals against certain bacterial infections, and its active sulfonamide component was later identified as sulfanilamide. Prontosil became a landmark in the development of systemic antibacterial chemotherapy.
Prontosil was not an antibiotic in the strict historical sense of a substance produced by a microorganism. It was a synthetic sulfonamide drug, so “synthetic antibacterial” is the more precise description. In everyday language, however, it is often grouped with early antibiotics.
Penicillin was discovered earlier but was developed for broad medical use later. Streptomycin also came afterward and became especially important against tuberculosis. Prontosil therefore represents a separate breakthrough: the first major synthetic antibacterial treatment before the antibiotic era fully expanded.