Phenazopyridine hydrochloride, an azo dye marketed in the US in 1914, became widely prescribed for the treatment of urinary tract infections (UTIs). With the assumption that the drug possessed antiseptic properties, phenazopyridine was recommended for UTIs caused by Staphylococcus, Streptococcus, and Escherichia coli. Although in the early 1930s the medical and scientific communities rescinded the claim that phenazopyridine is bactericidal, a specific mechanism of action has not been identified subsequently. Currently, phenazopyridine is classified as a urinary analgesic that relieves burning, urgency, frequency, and pain associated with UTI, trauma, or surgery.