Can Augmentin (amoxicillin-clavulanate) be given to a patient with a known allergy to cephalexin (cephalosporin)?

From the Guidelines

No, you should not take Augmentin if you are allergic to cephalexin, as both medications belong to related classes of antibiotics that can cause cross-reactivity in allergic individuals. According to the most recent study 1, patients with a suspected immediate-type allergy to cephalosporins can receive penicillins with dissimilar side chains, but it is recommended to avoid penicillins with similar side chains in patients with a suspected immediate-type allergy to cefalexin.

Key Considerations

• Augmentin contains amoxicillin (a penicillin-type antibiotic) plus clavulanic acid, while cephalexin is a cephalosporin antibiotic.
• Approximately 2-4.8% of patients with penicillin allergies may also react to cephalosporins, and vice versa, as reported in a study 1.
• This cross-reactivity occurs because both medication types share similar chemical structures, particularly in their beta-lactam rings.
• If you've had an allergic reaction to cephalexin, you should inform your healthcare provider about this allergy before taking any antibiotic.

Alternative Antibiotics

• Your doctor can prescribe alternative antibiotics from completely different classes, such as:
  • Macrolides (like azithromycin)
  • Fluoroquinolones (like ciprofloxacin)
  • Tetracyclines (like doxycycline)
• The choice of alternative antibiotic depends on the type of infection being treated.

Important Note

• It is essential to prioritize the patient's safety and avoid potential cross-reactivity when prescribing antibiotics, as emphasized in a study 1.

From the Research

Allergy Considerations

• A patient with a known allergy to cephalexin (a cephalosporin) may still be able to take Augmentin (amoxicillin-clavulanate), as the cross-reactivity between cephalosporins and penicillins is generally low 2, 3, 4, 5.
• The risk of cross-reactivity is related to the structural R1 side chain of the cephalosporin, and clinicians should be aware of these similarities when prescribing alternate β-lactams in allergic individuals 2, 3, 4.
• Studies have shown that the overall cross-reactivity rate between penicillins and cephalosporins is approximately 1% when using first-generation cephalosporins or cephalosporins with similar R1 side chains 4.
• However, some cephalosporins, such as cefadroxil, may have a higher cross-reactivity rate with penicillins, up to 27% in one study 4.
• Augmentin (amoxicillin-clavulanate) is a penicillin-based antibiotic, and its use in patients with a cephalosporin allergy has not been directly studied in the provided evidence.
• One study compared amoxicillin-clavulanic acid to cefaclor in the treatment of urinary tract infections, but did not specifically address the issue of cross-reactivity in patients with cephalosporin allergies 6.

Clinical Implications

• Clinicians should consider the low likelihood of true cephalosporin allergy when clinically indicated, and should not avoid the use of cephalosporins solely based on a reported penicillin allergy 2, 3, 5.
• The use of third- or fourth-generation cephalosporins or cephalosporins with dissimilar side chains than the offending penicillin carries a negligible risk of cross allergy 4, 5.
• However, caution should still be exercised when prescribing any antibiotic to a patient with a known allergy, and the patient should be closely monitored for signs of an allergic reaction.