Sulbactam

Sulbactam is a beta-lactamase inhibitor used in combination with beta-lactam antibiotics to extend their activity against beta-lactamase–producing bacteria. It has limited intrinsic antibacterial activity when used alone, and its clinical utility lies in protecting partner antibiotics from enzymatic degradation.

Mechanism and pharmacology: Sulbactam inhibits serine beta-lactamases produced by many Gram-negative and some Gram-positive bacteria. It acts as a substrate for these enzymes and forms a stable acyl-enzyme complex, thereby inactivating the enzyme and preserving the activity of the companion antibiotic. Sulbactam is administered parenterally and is primarily excreted unchanged by the kidneys, with dosing adjusted for renal function.

Common combinations and spectrum: The best-known formulation is ampicillin-sulbactam, marketed as ampicillin-sulbactam in several countries. This combination broadens coverage to include many beta-lactamase–producing strains of Haemophilus influenzae, Moraxella catarrhalis, and assorted Enterobacterales, as well as anaerobes such as Bacteroides fragilis. Sulbactam itself has limited activity against Pseudomonas aeruginosa and many resistant organisms, so activity against certain pathogens depends on the partner antibiotic. Sulbactam is also combined with cefoperazone in some regimens (cefoperazone-sulbactam) where available.

Indications and use: It is used for intra‑abdominal infections, gynecological infections, skin and soft tissue infections, and pneumonia where beta-lactamase production is a concern. Dosing is guided by the partner antibiotic and the site and severity of infection, with renal function taken into account.

Resistance and safety: Resistance may arise from beta-lactamases not inhibited by sulbactam, or from non-enzymatic mechanisms. Adverse effects are similar to other beta-lactams and may include hypersensitivity reactions, diarrhea, nausea, and rash. Caution is advised in patients with penicillin allergy due to potential cross-reactivity.