Oral Bioavailability: Cefuroxime Axetil vs Augmentin
Augmentin (amoxicillin-clavulanate) has superior oral bioavailability compared to cefuroxime axetil, with amoxicillin demonstrating excellent bioavailability that increases linearly with dose, while cefuroxime axetil achieves only 36-52% bioavailability in fasting and fed states respectively.
Comparative Bioavailability Data
Amoxicillin-Clavulanate (Augmentin)
- Amoxicillin exhibits excellent bioavailability with linear dose-dependent absorption, meaning gastrointestinal absorption is not a limiting factor regardless of dose magnitude 1
- The American Academy of Otolaryngology guidelines specifically note that serum levels of amoxicillin increase linearly with dose, allowing for effective high-dose regimens (up to 4 g/day in adults) 1
- This superior absorption profile makes amoxicillin "generally considered the most active of all oral β-lactams against streptococci, including pneumococci" when considering both intrinsic activity and bioavailability 1
Cefuroxime Axetil
- Absolute bioavailability ranges from 36% (fasting) to 52% (fed state) after a 500 mg dose 2
- Multiple studies confirm bioavailability in the 50-68% range, with considerable inter-individual variation 3, 4
- Food significantly enhances absorption: the fed dose achieves 43% greater peak plasma concentration compared to fasting 2
- Peak concentrations vary considerably (4.7-12.0 mg/L) with delayed time to peak (1.5-4 hours) 4
Clinical Implications of Bioavailability Differences
Why This Matters for Treatment Selection
The physicochemical properties of oral cephalosporins like cefuroxime axetil make them inherently less suitable than amoxicillin for pneumococcal infections 1. This is due to:
- Cephalosporins are actively absorbed in the gastrointestinal tract, which limits achievable concentrations regardless of dose administered 1
- Cephalosporins have baseline MICs against S. pneumoniae that are fourfold higher than amoxicillin, compounding the bioavailability disadvantage 1
- Amoxicillin's linear absorption allows dose escalation to overcome resistance, while cefuroxime's absorption ceiling prevents this strategy 1
Practical Dosing Considerations
- Cefuroxime axetil must be administered with food to optimize bioavailability (52% vs 36% fasting) 2
- Standard cefuroxime axetil dosing is 250-500 mg twice daily, with bioavailability of approximately 68% for the 500 mg tablet formulation when taken with meals 3
- High-dose amoxicillin-clavulanate (4 g amoxicillin/250 mg clavulanate daily for adults) achieves superior tissue concentrations due to unrestricted absorption 1
Antimicrobial Activity Context
While bioavailability is critical, the guidelines emphasize that high-dose amoxicillin-clavulanate achieves 95-97% activity against S. pneumoniae based on PK/PD breakpoints, compared to only 63-75% for cefuroxime axetil 1. Against H. influenzae, amoxicillin-clavulanate achieves 95-100% coverage versus 70-85% for cefuroxime axetil 1.
Common Pitfalls to Avoid
- Do not assume equivalent efficacy based on dose alone—cefuroxime's limited bioavailability and active absorption mechanism prevent dose escalation strategies that work with amoxicillin 1
- Always administer cefuroxime axetil with food—fasting administration reduces bioavailability by approximately 30% 2
- Recognize that cefuroxime's unpalatable suspension formulation significantly limits pediatric adherence, further compromising clinical outcomes 5