Susceptibility Testing: Cefuroxime Sodium vs. Cefuroxime Axetil
Yes, susceptibility to cefuroxime sodium reliably indicates susceptibility to cefuroxime axetil, as both formulations release the same active parent compound (cefuroxime) and share identical antimicrobial spectra. 1, 2
Pharmacological Basis for Equivalent Susceptibility
Cefuroxime axetil is an acetoxyethyl ester prodrug that is rapidly hydrolyzed to the active parent compound cefuroxime after oral administration. 3, 2
Both cefuroxime sodium (parenteral) and cefuroxime axetil (oral) release the same active antibacterial agent, resulting in identical in vitro antibacterial activity against susceptible organisms. 2
The antimicrobial spectrum encompasses methicillin-sensitive staphylococci, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, group A beta-hemolytic streptococci, and common Enterobacteriaceae including E. coli, Klebsiella pneumoniae, and Proteus mirabilis. 3, 2
Clinical Laboratory Evidence
Susceptibility data from the CDC's Active Bacterial Core Surveillance demonstrates that cefuroxime sodium and cefuroxime axetil have nearly identical resistance patterns against S. pneumoniae isolates stratified by penicillin susceptibility (19.5% vs. 20.6% resistance rates respectively). 1
This minimal difference (1.1%) in resistance rates reflects testing methodology variations rather than true differences in antimicrobial activity, confirming that susceptibility results are interchangeable between formulations. 1
Important Clinical Caveat
The key distinction between formulations is bioavailability, not antimicrobial activity—cefuroxime axetil tablets achieve 68% absolute bioavailability (range 63-73%) after oral administration, meaning lower serum concentrations compared to equivalent parenteral doses. 3
For severe infections requiring higher tissue concentrations (e.g., meningitis, severe pneumonia), parenteral cefuroxime sodium is preferred despite identical susceptibility profiles, because oral bioavailability may be insufficient to achieve therapeutic concentrations at the infection site. 4
Sequential IV-to-oral therapy studies demonstrate that switching from parenteral cefuroxime sodium to oral cefuroxime axetil after 2 days maintains therapeutic efficacy in lower respiratory tract infections, confirming that susceptibility testing applies equally to both formulations when adequate serum levels are achieved. 2