The tetracycline group of anti-infectives is composed of three drugs, which are derived from the common soil mold, Streptomyces (demeclocycline [Declomycin], oxytetracycline [Terramycin], and tetracycline [Acromycin]), as well as two other drugs that are semi-synthetically derived (doxycycline [Vibramycin] and minocycline [Minocin]). This group of medications is bacteriostatic, broad-spectrum, and needs the body’s defense mechanisms to actually kill bacteria. All tetracyclines can bind to divalent and trivalent metallic ions such as aluminum, calcium, and magnesium. Thus, they should not be administered with substances that contain these ions as this results in decreased absorption of tetracycline. A great deal of microbial resistance has developed against this group over the years, and newer medications have been developed that are less toxic and more effective. However, the tetracyclines are still the drug of choice for a number of specific infections. They are well distributed to most body fluids and tissues except for cerebral spinal fluid and are excreted by the kidney and liver.