carboxypenicillin

Carboxypenicillins are a subclass of beta-lactam antibiotics within the penicillin family. They are characterized by carboxylated side chains and are primarily active against certain Gram-negative bacteria. The main representatives are carbenicillin and ticarcillin, with various salt forms or prodrugs used to influence administration and absorption. These agents are generally effective against several Enterobacteriaceae and Pseudomonas aeruginosa, but they are more limited against Gram-positive organisms and many anaerobes.

The mechanism of action of carboxypenicillins mirrors other beta-lactams: they inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to bactericidal effects. Their spectrum favors Gram-negative rods, including Pseudomonas, Proteus, Escherichia coli, and Klebsiella species, while activity against non-enteric Gram-negatives and resistant strains is variable. Many beta-lactamases can hydrolyze carboxypenicillins, reducing activity against organisms that produce these enzymes. In some regions, combinations with beta-lactamase inhibitors (such as ticarcillin-clavulanate) have been developed to broaden coverage.

Pharmacokinetics commonly involve parenteral administration for ticarcillin, while carbenicillin was also available in oral prodrug form (carbenicillin indanyl). Both are typically excreted renally, requiring dosing adjustments in renal impairment. Side effects align with the broader penicillin class and can include hypersensitivity reactions, gastrointestinal upset, and electrolyte disturbances in certain regimens (notably with high-dose or sodium-containing formulations).

Historically, carboxypenicillins were used to treat serious Gram-negative infections, including Pseudomonas aeruginosa and respiratory infections. Their use has declined with the availability of broader-spectrum agents and fortified beta-lactamase–resistant combinations, but they remain relevant in discussions of penicillin-class diversity and the evolution of anti-pseudomonal therapy.