Doxycycline is an antibiotic in the class of tetracyclines. It has a broad spectrum of activity and shows a bacteriostatic effect on gram-positive, gram-negative bacteria and cell walls. Likewise, it is effective against Plasmodium sp. , but shows little tuberculostatic effectiveness. According to its spectrum is doxycycline for the treatment of respiratory diseases, infections of the urogenital tract, infections of the gastrointestinal tract, bile duct, acne, rosacea, chlamydial infections, Lyme disease, as well as numerous rare infections, such as used, for example, plague and anthrax.