Classification of Faropenem
Faropenem is classified as a penem, which is a distinct class of beta-lactam antibiotics that represents a structural hybrid between penicillins (penams) and cephalosporins (cephems). 1
Characteristics of Penems and Faropenem's Position
Penems form their own discrete class within the beta-lactam family, separate from the following major beta-lactam classes:
- Penicillins (penams)
- Cephalosporins (cephems)
- Carbapenems
- Monobactams
Faropenem specifically has the following distinguishing features:
- It is an orally active beta-lactam antibiotic 2
- Contains a C-2 tetrahydrofuran (THF) ring that provides resistance to hydrolysis by some beta-lactamases 3
- Has a different spectrum of activity compared to carbapenems, with penems generally covering community pathogens while carbapenems cover hospital pathogens 1
Antimicrobial Spectrum and Properties
Faropenem demonstrates:
- Exceptionally broad spectrum of antibacterial activity 1
- Intrinsic stability against hydrolytic attack by many beta-lactamases including ESBL and AmpC enzymes 1
- High activity against anaerobic pathogens (MIC₉₀ ≤ 0.5 mg/L) 2
- Bactericidal activity against both beta-lactamase-positive and -negative anaerobes 2
- Post-antibiotic effect (PAE) on tested isolates, unaffected by beta-lactamase production 2
Clinical Significance and Advantages
Faropenem offers several advantages that differentiate it from other beta-lactams:
- Low propensity for resistance development 1
- Low beta-lactamase induction potential 1
- Reduced selection of carbapenem-resistant Pseudomonas aeruginosa 1
- Suitable for community-acquired infections 1
- Potential for step-down or sequential therapy following carbapenem treatment 1
- Preserves activity of carbapenems in hospital settings 1
Mechanism of Action
Like other beta-lactams, faropenem works by binding to penicillin-binding proteins (PBPs) in bacterial cell walls, inhibiting cell wall biosynthesis, and causing bacterial cell lysis and death 4.
Unique Biochemical Properties
Faropenem has unique interactions with beta-lactamases:
- Forms imine products when reacting with both serine and metallo-β-lactamases 3
- Shows complex reaction patterns with various beta-lactamases, including THF ring opening in some cases 3
- These complex interactions may contribute to its stability against certain beta-lactamases 3
In summary, faropenem belongs to the penem class of beta-lactam antibiotics, which is distinct from penicillins, cephalosporins, carbapenems, and monobactams, with unique structural features and antimicrobial properties that make it particularly suitable for community-acquired infections.