Drug of choice to treat adult periodontitis is:

• A. Tetracycline
• B. Erythromycin
• C. Amoxicillin
• D. Doxycycline

Answer: (A)

When treating adult periodontitis, an antibiotic is chosen for its ability to reach high levels in the gingival crevicular fluid and to help limit tissue destruction in addition to lowering the subgingival bacterial load. Tetracycline fits this best because it concentrates well in gingival crevicular fluid, has broad activity against the typical periodontal pathogens, and can inhibit host-derived collagenases that drive connective tissue breakdown. This combination of effective pocket penetration, antimicrobial action against key organisms, and the added benefit of dampening tissue destruction makes tetracycline the preferred choice in this context. Erythromycin often has less reliable anaerobic coverage and resistance issues, amoxicillin may not achieve the same crevicular fluid levels or anti-collagenase effects, and while doxycycline is also effective, the classic teaching emphasizes the tetracycline class for these advantages.