prontosil

noun

pron·​to·​sil ˈprän-tə-ˌsil 

: any of three sulfonamide drugs:

a

: a red azo dye C₁₂H₁₃N₅O₂S that was the first sulfa drug tested clinically

called also prontosil rubrum

b

: sulfanilamide

c

: azosulfamide