For years periodontics has recognized that bacteria, their by products and the body's reaction to  all three of these are the causes for periodontal disease.  Systemic (taken by mouth)  and local drug delivery are modalities where antibiotics can be helpful. 

Antibiotic therapy is not indicated in all cases of periodontitis.  They are usually reserved for more aggressive and refractory foms of the disease.  They are considered adjuncts to non - surgical and surgical periodontal treatments and they have risks of allergic and adverse drug reactions.

Commonly used systemic medications are amoxicillin, doxycycline, metronidazole, and tetracycline.