: a yellow crystalline broad-spectrum antibiotic that is produced by a soil actinomycete of the genus Streptomyces (S. viridifaciens) or made synthetically and that is administered chiefly in the form of its hydrochloride C22H24N2O8·HCl; also: any of several chemically related antibiotics (as doxycycline)
Any of a class of broad-spectrum antibiotics with a common basic structure, including doxycycline. They may be isolated directly from several species of actinomycetes of the genus Streptomyces or modified from the compounds isolated. They are the drugs of choice in the treatment of cholera, rickettsial infections (seerickettsia), psittacosis, brucellosis, and tularemia; tetracyclines are also used in the treatment of acne. Overuse of these and other antibiotics has led to drug resistance in microorganisms.