Why are ampicillin and amoxicillin often co-formulated with clavulanate in clinical products?

• A. Because clavulanate competitively inhibits human serum proteases that would otherwise inactivate amoxicillin systemically, thereby increasing systemic half-life rather than targeting bacterial resistance enzymes.
• B. Because clavulanate acts as a membrane-permeabilizing agent that widens all porins, allowing ampicillin and amoxicillin to reach intracellular targets even in organisms that lack the necessary PBPs.
• C. Because clavulanate chelates divalent ions required for peptidoglycan cross-linking, acting synergistically with ampicillin by independently blocking PBP active sites and eliminating the need to inhibit beta-lactamases.
• D. Because the amino-group modifications enable these drugs to pass Gram-negative porins and reach PBPs, but they remain vulnerable to many beta-lactamases; clavulanate inhibits those enzymes, restoring antibiotic efficacy.

Answer: (D)