Antibiotic.   Cefalexin (INN, BAN) or is an antibiotic useful for the treatment of a number of bacterial infections. It is taken by mouth and is active against gram positive bacteria and some gram negative bacteria. It is in the class of first generation cephalosporins and has similar activity to other agents within this group including the intravenous agent cefazolin.Cefalexin is used to treat a number of bacterial infections including: middle ear infections, strep throat, bone and joint infections, pneumonia, skin infections, and urinary tract infections. It may be used to prevent bacterial endocarditis. It is ineffective against methicillin-resistant Staphylococcus aureus. It may be used in those who have mild or moderate allergies to penicillin but is not recommended is those with severe allergies. It has no effect against viral infections.  Possible side effects include: allergies, stomach and intestinal upset, and Clostridium difficile diarrhea among others.] It is pregnancy category B in the United States and category A in Australia meaning that there is no evidence of harm after being taken by many pregnant women. Use during breast feeding is okay. It is suitable for use in children and those over 65 years of age. Doses may need to be decreased in those with kidney problems .  Ref:  Lab Brufuagsa. Antibiotic. Pneumonia. Infections. Anti bacterial