Ampicillin/sulbactam is a combination of the common penicillin-derived antibioticampicillin and sulbactam, an inhibitor of bacterialbeta-lactamase. Two different forms of the drug exist. The first, developed in 1987 and marketed in the United States under the tradename Unasyn, generic only outside of the United States, is an intravenous antibiotic. The second, an oral form called sultamicillin, is marketed under the trade name Ampictam outside of the United States. And generic only in the United States, ampicillin/sulbactam is used to treat infections caused by bacteria resistant to beta-lactam antibiotics. Sulbactam blocks the enzyme which breaks down ampicillin and thereby allows ampicillin to attack and kill the bacteria.