Sulfanilamide and it derivative sulfa drugs are bacteriostatic, gaining their effectiveness by interfering with the enzymatic systems of bacteria and inhibiting their ability to grow or multiply. Due to the capacity of some bacteria to adapt in such a way that makes them resistant to this bacteriostatic action, a tremendous number of the sulfa drugs that originally appeared to be effective, no longer exhibit antibacterial action. Moreover, the toxicity of many sulfonamides, which some individuals are hypersensitive to, has also limited their use in recent years as the array of safer antibiotics available has expanded. Nevertheless, some sulfa drugs are still commonly utilized in the treatment of certain medical conditions, especially vulvovaginitis and urinary tract infections.