12 Reviews. Cephalexin, an antibiotic in the cephalosporin family, is used to treat infections caused by bacteria. Cephalexin is prescribed to treat respiratory tract, middle ear, skin, bone, and urinary tract infections (UTI).It's also used to prevent infections caused by streptococcal bacteria, including prevention of rheumatic fever. Cephalexin isn't recommended for sinus infections.Cephalexin is sometimes called a first-generation cephalosporin because it was one of the first cephalosporins developed and marketed.t's also used to prevent infections caused by streptococcal bacteria, including prevention of rheumatic fever. Cephalexin isn't recommended for sinus infections. Cephalexin is sometimes called a first-generation cephalosporin because it was one of the first cephalosporins developed and marketed.