Epicillin: in vitro laboratory studies.

A new semisynthetic penicillin, structurally related to ampicillin, has been assigned the generic name epicillin, 6-[d-2-amino-2-(1, 4-cyclohexadienyl) acetamido]-penicillanic acid. The antimicrobial spectrum and level of activity of epicillin in vitro are similar to those of ampicillin. In studies with recent clinical isolates, these two antibiotics, when compared with carbenicillin, showed consistently higher antimicrobial activity against Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Proteus species. When tested against Pseudomonas aeruginosa isolates, on the other hand, epicillin exhibited a level of intrinsic activity superior to that of ampicillin but less than that of carbenicillin. Epicillin is an amphoteric substance that is sensitive to penicillinase, is acid-stable, and is minimally, but reversibly, bound to human serum protein.