Doxycycline is an antibiotic related to tetracycline. It is a broad-spectrum antibiotic and can be used against a wide variety of bacterial infections. One of its advantages is that in its pill form, it only has to be taken once per day to have the appropriate effect. It is strongly indicated if the patient has anthrax, plague or Lyme disease. It is one of the few antibiotics that is effective against Rocky Mountain spotted fever.
Along with the side effects typical of other antibiotics, doxycycline also can result in photosensitive skin reactions, so it should be avoided for long term use. It is also not appropriate for children under the age of 8 due to its effect on bone and tooth development. However, it is indicated for patients who have kidney problems as it causes less kidney damage than other similar antibiotics.