prontosil
noun
pron·to·sil
| \ ˈprän-tə-ˌsil
\
\
Medical Definition of prontosil
: 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