Macrobid is an antibiotic that is prescribed for cystitis and other urinary tract infections. The active substance is nitrofurantoin, an anti-bactericidal medication that is rapidly and almost completely excreted by the kidneys.
Keflex (Cephalexin) is a drug that fights bacteria in the body. Its active ingredient is cefalexin and belongs to the class of cephalosporins. The medication kills bacteria and inhibits the growth of these micro-organisms.
Zithromax contains the active ingredient azithromycin, which is a type of medicine called a macrolide antibiotic. Azithromycin works by preventing bacteria from producing proteins that are essential to them.