Arestin (minocycline HCl) Microspheres, 1 mg. is an antibiotic that helps kill the bacteria that cause gum disease at the root of the problem. These microspheres are smaller than grains of sand and are not visible to the eye.  Arestin is different from antibiotic pills that a person swallows because Arestin is placed right where you need it, delivering the antibiotic directly to your gums. Arestin is placed during the scaling and root planning visit immediately after all the plaque and calculus is removed. Arestin therapy is done in conjunction with root planning and scaling to increase its effectiveness and is not meant to be an alternative therapy.