Ampicillinsulbactam

Ampicillin-sulbactam is a combination antibiotic that pairs the beta-lactam antibiotic ampicillin with the beta-lactamase inhibitor sulbactam. The sulbactam component helps protect ampicillin from certain bacterial enzymes, expanding its activity against beta-lactamase–producing strains. The product is most commonly administered by intravenous or intramuscular injection and is available under brand names such as Unasyn in many markets. An oral prodrug form called sultamicillin exists in some regions.

Mechanism and spectrum: Ampicillin inhibits bacterial cell wall synthesis by binding penicillin-binding proteins, while sulbactam inhibits specific beta-lactamases produced by certain bacteria. This combination provides coverage against a broader range of organisms than ampicillin alone, including many beta-lactamase–producing strains of Haemophilus influenzae, Moraxella catarrhalis, and some anaerobes such as Bacteroides fragilis. It retains activity against many enteric Gram-negative rods and streptococci. It has limited activity against Pseudomonas aeruginosa and is not reliable against MRSA or many other resistant organisms.

Indications and administration: Ampicillin-sulbactam is used for a variety of infections, including intra-abdominal and gynecologic infections, skin and soft tissue infections, pneumonia, and other serious infections where beta-lactamase producing organisms are suspected. Dosing is typically adjusted for infection severity and renal function, with adults usually receiving 1.5 g to 3 g per dose every 6 hours by IV or IM administration.

Adverse effects and cautions: Common adverse effects include diarrhea, rash, and hypersensitivity reactions. Potential concerns include superinfections, C. difficile–associated diarrhea, and phlebitis at the infusion site. Contraindications include a known penicillin allergy or hypersensitivity to beta-lactamase inhibitors. Renal impairment requires dose adjustment, and cross-reactivity in penicillin-allergic patients should be considered.