From the FDA Drug Label
Cephalexin has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections... Aerobes, Gram-positive: Staphylococcus aureus (including penicillinase-producing strains)
- Key point: Cephalexin is active against penicillinase-producing strains of Staphylococcus aureus.
- Beta-lactamase stability: This suggests that cephalexin has greater beta-lactamase stability than amoxicillin, as it is effective against bacteria that produce beta-lactamase, an enzyme that breaks down amoxicillin 1.
- Comparison to amoxicillin: Amoxicillin is not mentioned in the provided drug label, but based on the information about cephalexin's activity against penicillinase-producing strains, it can be inferred that cephalexin may have an advantage over amoxicillin in terms of beta-lactamase stability.
From the Research
Keflex (cephalexin) has greater beta-lactamase stability than amoxicillin, as evidenced by its classification as a first-generation cephalosporin, which generally exhibits better resistance to beta-lactamase enzymes compared to penicillins like amoxicillin 2.
Key Points
- Beta-lactamases are enzymes produced by certain bacteria that can break down the beta-lactam ring structure of antibiotics, rendering them ineffective.
- The molecular structure of cephalosporins provides them with inherently greater stability against these enzymes.
- This is why Keflex may be effective against some amoxicillin-resistant strains of bacteria, particularly those that produce beta-lactamases.
- However, for more severe beta-lactamase-producing infections, neither drug may be adequate, and either a beta-lactamase inhibitor combination (like amoxicillin-clavulanate) or a higher-generation cephalosporin might be needed.
Considerations
- The choice between Keflex and amoxicillin should be based on the suspected pathogen and local resistance patterns, as they have different antimicrobial spectrums.
- Newer oral cephalosporins, such as cefdinir and cefpodoxime, have been shown to have improved activity against certain pathogens and stability against beta-lactamases compared to older cephalosporins like cephalexin 3.
- The use of beta-lactamase inhibitors in combination with beta-lactam antibiotics has been an effective strategy to circumvent resistance issues 2.