This is the persistence of antibiotic effect observed long after the serum concentration has fallen below the MIC. It is seen in antibiotics which inhibit some life-sustaining enzyme, or which bind tightly to cell wall components.

The post-antibiotic effect has some relationship to the kill characteristics of the antibiotic, but the relationship is not straightforward. For instance, macrolides are known for time-dependent kill characteristics, but have a strong post-antibiotic effect which probably inhibits bacterial growth rather than causing cell lysis.

Strong post-antibiotic effect

This is mainly seen in drugs which have concentration-dependent kill characteristics.

Such drugs benefit from large intermittent doses; high peak concentrations translate into better post-antibiotic effects.

 

Moderate post-antibiotic effect

This is seen in drugs which have time-dependent kill characteristics

  • Carbapenems
  • Fluoroquinolones
  • Glycopeptides
  • Linezolid

Weak or absent post-antibiotic effect

This is usually a feature of drugs which act at some critical point in the bacterial reproductive cycle.

The drug must therefore be present in the over-MIC concentration at that critical point.

Such drugs include:

  • β-lactams
  • Cephalosporins
  • Monobactams

Theoretically, such drugs might benefit from continuous infusions rather than intermittent doses.

References

Oh's Intensive Care Manual: Chapter 72  (pp. 738)  Principles  of  antibiotic  use  by Jeffrey  Lipman

Roberts, Jason A., and Jeffrey Lipman. "Pharmacokinetic issues for antibiotics in the critically ill patient." Critical care medicine 37.3 (2009): 840-851.

Craig, William A. "Basic pharmacodynamics of antibacterials with clinical applications to the use of β-lactams, glycopeptides, and linezolid." Infectious disease clinics of North America 17.3 (2003): 479-501.

Craig, William A. "Pharmacokinetic/pharmacodynamic parameters: rationale for antibacterial dosing of mice and men." Clinical infectious diseases (1998): 1-10.

Craig, William A. "Interrelationship between pharmacokinetics and pharmacodynamics in determining dosage regimens for broad-spectrum cephalosporins." Diagnostic microbiology and infectious disease 22.1 (1995): 89-96.

Weinstein, Melvin P., et al. "Multicenter collaborative evaluation of a standardized serum bactericidal test as a predictor of therapeutic efficacy in acute and chronic osteomyelitis." The American journal of medicine 83.2 (1987): 218-222.

Leggett, J. E., et al. "Comparative antibiotic dose-effect relations at several dosing intervals in murine pneumonitis and thigh-infection models." Journal of infectious diseases 159.2 (1989): 281-292.

Moore, Richard D., Paul S. Lietman, and Craig R. Smith. "Clinical response to aminoglycoside therapy: importance of the ratio of peak concentration to minimal inhibitory concentration." Journal of Infectious Diseases 155.1 (1987): 93-99.

Daikos, GEORGE L., VALENTINA T. Lolans, and G. G. Jackson. "First-exposure adaptive resistance to aminoglycoside antibiotics in vivo with meaning for optimal clinical use." Antimicrobial agents and chemotherapy 35.1 (1991): 117-123.

MacKenzie, F. M., and I. M. Gould. "The post-antibiotic effect." Journal of Antimicrobial Chemotherapy 32.4 (1993): 519-537.

Athamna, A., et al. "In vitro post-antibiotic effect of fluoroquinolones, macrolides, β-lactams, tetracyclines, vancomycin, clindamycin, linezolid, chloramphenicol, quinupristin/dalfopristin and rifampicin on Bacillus anthracis."Journal of Antimicrobial Chemotherapy 53.4 (2004): 609-615.

Stubbings, William J., et al. "Assessment of a microplate method for determining the post-antibiotic effect in Staphylococcus aureus and Escherichia coli." Journal of Antimicrobial Chemotherapy 54.1 (2004): 139-143.

Woodnutt, Gary. "Pharmacodynamics to combat resistance." Journal of antimicrobial chemotherapy 46.suppl 3 (2000): 25-31.