Periostat is a brand name for the medication doxycycline hyclate, which belongs to a class of drugs known as tetracycline antibiotics. It is specifically formulated as a low-dose, slow-release tablet that is used primarily in the treatment of periodontitis, a severe gum infection that can lead to tooth loss if left untreated. Unlike higher doses of doxycycline that act as antibiotics, the low dose of Periostat is used not to kill bacteria directly but to inhibit the activity of certain enzymes (collagenases) that break down periodontal tissue. This helps control the progression of the disease by reducing the destruction of the gum tissue and promoting the stability of the teeth. It is often prescribed as part of a comprehensive dental treatment plan that includes good oral hygiene practices and regular dental check-ups.