Tetracycline antibiotics (minocycline, doxycycline) are used in periodontal treatment because they concentrate in which fluid?

Correct answer: C. Gingival crevicular fluid (GCF)

• A. While tetracyclines are distributed in plasma, their specific advantage in periodontics is GCF concentration.
• B. Urinary concentration is relevant for UTI treatment — not for periodontal benefit.
• C. Correct. Tetracyclines (doxycycline/Periostat, Atridox; minocycline/Arestin) concentrate in the gingival crevicular fluid at levels 2-10x higher than serum. This allows targeted delivery to periodontal pockets. They also inhibit matrix metalloproteinases (MMPs), reducing collagen destruction.
• D. Tetracyclines concentrate in GCF, not primarily in saliva for their periodontal effect.