Doxycyclez 100^TM is a member of the tetracycline antibiotics group and is commonly used to treat a variety of infections. Doxycycline is a semi-synthetic tetracycline. It is also effective against Yersinia pestis (the infectious agent of bubonic plague) and is prescribed for the treatment of Lyme disease, ehrlichiosis and Rocky Mountain spotted fever. In fact, because doxycycline is one of the few medications shown to be effective in treating Rocky Mountain spotted fever (with the next best alternative being chloramphenicol), doxycycline is indicated even for use in children for this illness. Otherwise, doxycycline is not indicated for use in children under the age of 8 years. Doxycycline, like other antibiotics, will not work for colds, flu, or other viral infections.