Augmentin Penetrates Better Than Amoxicillin in Beta-Lactamase Producing Bacterial Infections
Augmentin (amoxicillin-clavulanic acid) penetrates better than amoxicillin alone in infections caused by beta-lactamase producing bacteria because the clavulanic acid component preserves the activity of amoxicillin by inhibiting beta-lactamases. 1, 2
Mechanism of Action and Penetration
- Amoxicillin is a beta-lactam antibiotic that inhibits cell-wall synthesis but is susceptible to degradation by beta-lactamases produced by resistant bacteria 2
- Clavulanic acid is a beta-lactamase inhibitor that possesses the ability to inactivate a wide range of beta-lactamase enzymes commonly found in resistant microorganisms 2
- When combined with amoxicillin, clavulanic acid protects amoxicillin from degradation by beta-lactamases, effectively extending its spectrum of activity to include many bacteria that would otherwise be resistant 2, 3
Comparative Effectiveness Against Beta-Lactamase Producing Bacteria
- While amoxicillin alone has excellent intrinsic activity against streptococci (including pneumococci), it is ineffective against beta-lactamase producing organisms 1
- Augmentin maintains the same intrinsic activity against non-beta-lactamase producing organisms as amoxicillin, but adds effectiveness against beta-lactamase producing strains 1, 4
- The addition of clavulanate to amoxicillin significantly enhances activity against beta-lactamase-producing strains of Haemophilus influenzae, Moraxella catarrhalis, and other beta-lactamase producing organisms 1, 5
Clinical Implications
- For infections where beta-lactamase producing bacteria are suspected or confirmed, Augmentin provides superior penetration and effectiveness compared to amoxicillin alone 1, 3
- In diabetic foot infections that have progressed or failed initial management, broader spectrum antibiotics like amoxicillin-clavulanic acid are appropriate to cover beta-lactamase producing organisms 1
- For respiratory tract infections, the relative antimicrobial activity against beta-lactamase producing H. influenzae and M. catarrhalis is significantly higher with amoxicillin-clavulanic acid (95-100%) compared to amoxicillin alone (70-85% for H. influenzae and only 20% for M. catarrhalis) 1
Formulation Considerations
- Extended-release and high-dose formulations of amoxicillin-clavulanic acid provide pharmacokinetically enhanced versions that maintain therapeutic concentrations over longer periods 1, 5
- The adult formulation of high-dose Augmentin uses a modified-release mechanism that provides both immediate and sustained release of amoxicillin while maintaining clavulanate protection 1, 5
- These formulations are particularly valuable for treating infections caused by organisms with reduced susceptibility to standard doses 6
Common Pitfalls and Caveats
- Amoxicillin-clavulanic acid may cause more gastrointestinal side effects than amoxicillin alone, particularly when administered three times daily 1, 6
- The incidence of gastrointestinal side effects is significantly reduced with twice-daily dosing regimens 1, 6
- In certain severe infections like inhalational anthrax, even amoxicillin-clavulanic acid may not be clinically effective when large numbers of organisms are present, despite in vitro activity 1
- For infections where beta-lactamase production is not a concern, amoxicillin alone may be sufficient and could reduce the risk of side effects 1, 7
Summary of Evidence
- Augmentin provides superior penetration against beta-lactamase producing bacteria compared to amoxicillin alone by protecting amoxicillin from enzymatic degradation 1, 2, 3
- The combination extends the spectrum of activity to include previously resistant organisms while maintaining the same effectiveness against susceptible bacteria 2, 4
- For infections where beta-lactamase producing organisms are suspected, Augmentin is the preferred choice over amoxicillin alone 1, 5