In the formulation amoxicillin-clavulanate, which beta-lactamase inhibitor is combined with amoxicillin?

• A. Sulbactam
• B. Clavulanic acid
• C. Avibactam
• D. Tazobactam

Answer: (B)

The key idea is that beta-lactamase inhibitors are combined with beta-lactam antibiotics to protect the antibiotic from enzymatic destruction by bacteria. In amoxicillin-clavulanate, the inhibitor is clavulanic acid. Clavulanic acid binds to many beta-lactamases and inactivates the enzymes, effectively shielding amoxicillin so it can still reach its target—penicillin-binding proteins—inside bacteria. This broadens amoxicillin’s activity to include many beta-lactamase–producing organisms that would normally degrade the drug. Clavulanic acid herself has little antibacterial effect on its own, but its inhibitory action is what makes the combination useful. Other beta-lactamase inhibitors exist in different antibiotic combos (such as with ampicillin, piperacillin, or ceftazidime), but for amoxicillin, clavulanic acid is the inhibitor used.