Tetracycline drugs are effective against many bacterial infections.
They are commonly prescribed to treat urinary infections, chlamydial infection, pneumonia, brucellosis, and rickettsial diseases, such as typhus. Tetracyclines may also be used to treat bacterial infections in patients who are sensitive to penicillin. Bacteria may become resistant to tetracyclines, but this does not usually occur during a short course of treatment. Treatment with tetracyclines may produce nausea, vomiting, and diarrhea. Allergic reactions are extremely rare.