A  

Sub-antimicrobial-dose doxycycline (SDD) is defined as 20 mg doxycycline given once or twice daily; this low dose modulates host inflammatory enzymes without exerting antibacterial effects, and is the formulation approved for adjunctive periodontal therapy [Preshaw et al., 2004, PMID 15312090; Golub et al., 2001, PMID 11168739].