Mechanism of Action of Doxycycline
Doxycycline inhibits bacterial protein synthesis by reversibly binding to the 30S ribosomal subunit, which prevents the binding of transfer RNA (t-RNA) to the ribosome. 1, 2
Primary Antimicrobial Mechanism
Doxycycline acts as a bacteriostatic agent by blocking bacterial protein synthesis at the ribosomal level, specifically targeting the 30S subunit of bacterial ribosomes. 1, 2
The reversible binding to the 30S ribosomal subunit prevents aminoacyl-tRNA from attaching to the ribosome's acceptor site, thereby halting the elongation of the peptide chain during protein synthesis. 1
This mechanism provides broad-spectrum activity against both gram-positive and gram-negative organisms, as well as intracellular pathogens including Chlamydia, Mycoplasma, Rickettsia, and others. 2, 3
Anti-Inflammatory Properties
Beyond its antimicrobial effects, doxycycline possesses significant anti-inflammatory properties that are independent of its antibacterial action. 1
The anti-inflammatory mechanisms include:
These anti-inflammatory properties make doxycycline effective for treating non-infectious dermatologic conditions such as acne vulgaris and rosacea, often at subantimicrobial doses. 1, 4
Clinical Pharmacology Considerations
Doxycycline is virtually completely absorbed after oral administration (approximately 75% bioavailability), with peak serum levels achieved within 2 hours. 2, 5
The drug has excellent tissue penetration due to its lipophilic properties, allowing high concentrations in various tissues and organs. 2, 3
Unlike other tetracyclines, doxycycline has a long elimination half-life of 18-22 hours, permitting once or twice-daily dosing. 2, 3