Carbenicillin: Clinical and Laboratory Studies

Carbenicillin (a-carboxypenicillin) is a semi-synthetic penicillin presently available only as an investigational drug. It has shown considerable activity in vitro against many gram-negative organisms including Pseudomonas and Proteus species [1, 2]. A number of preliminary studies have shown it to be effective clinically in infections due to gram-negative rods and to be of low toxicity in both animals and humans [1, 2]. The drug is not well absorbed when administered orally and must be given parenterally [3]. One problem in the management of infections due to Pseudomonas has been the toxicity of the antibiotics effective against that organism [4, 5]. The lack of serious toxicity and the promise of considerable clinical effectiveness led us to study the value of therapy with carbenicillin for serious infections due to gram-negative organisms. Twenty-seven patients were treated for 29 infections, most of which were caused by Pseudomonas organisms. Nine were bronchopneumonias that occurred in patients with cystic fibrosis. In addition, the susceptibilities of a large number of grampositive and gram-negative organisms to carbenicillin were determined by both the paper-disk and tube-dilution techniques.