Doxycycline is a tetracycline derivative. When it is dosed at 20 mg twice daily, the resulting plasma levels are below those required for an antimicrobial effect; therefore, the mechanism of action of this antibiotic is not antimicrobial, it reduces or inhibits the activity of collagenase, an enzyme produced by the body as a part of its host immune response to a bacterial challenge. For chronic periodontitis patients, when used in addition to SRP, sub-antimicrobial doxycycline is more effective than SRP alone for reducing probing pocket depth and for gaining clinical attachment. Tolerability was similar to placebo, but the usual tetracycline safety limitations apply. For example, systemic doxycycline is neither indicated for pregnant or nursing patients, nor for patients hypersensitive to tetracyclines. Additionally, compliance may not be optimal over the entire treatment period. This is an important new option to be considered for chronic periodontitis patients and the available evidence suggests it significantly increases the chance for better outcomes than SRP alone.18,19 Other host response modulating therapies have been studied including topical and systemically administered non-steroidal anti-inflammatory drugs (NSAID's). Agents such as triclosan and bisphosphonates have been studied due to their potential to interfere with the periodontal disease process. Bisphosphonates may help inhibit bone loss.