Sulfamonomethoxine-d3 is the deuterium labeled Sulfamonomethoxine. Sulfamonomethoxine is an orally active sulfonamide antibiotic for veterinary use. Sulfamonomethoxine is also an inhibitor of dihydropteroate synthetase, which can block the synthesis of folic acid. Sulfamonomethoxine has antibacterial activity[1][2].