Sulfisoxazole, an endothelin receptor antagonist, is a sulfonamide antibacterial with an oxazole substituent. Target: Antibacterial; Endothelin Receptor The sulfanilamide antibacterial agent sulfisoxazole was found to be a good endothelin receptor antagonist (IC50's of 0.60 microM and 22 microM for the ETA and ETB receptors, respectively) [1]. Sulfisoxazole is used to treat or prevent infections in many different parts of the body. It belongs to the group of medicines known as sulfonamide antibiotics. It works by preventing the growth of bacteria [2].