Pharmacology of Systemic Antibacterial Agents
Pharmacological strategies are predicated on targeting differences between prokaryotic bacterial and eukaryotic host cells. Selective toxicity can be achieved by (1) attacking targets unique to bacteria, (2) attacking targets in bacteria similar but not identical to those in host cells, and (3) attacking targets that are shared, but vary in importance between bacteria and host cells (Figure 5).32 Drugs targeting unique differences are the least toxic to host cells.
Figure 5. Mechanisms of Action of Antibacterial Agents.
Based on Harbison H, Rose HS, Coen DM, Golan DE. Principles of antibacterial and antineoplastic pharmacology. In Golan DE, Tashjian, Jr. AH, Armstrong EJ, Armstrong AW. Ed. Principles of pharmacology. The pathophysiologic basis of drug therapy. 2nd ed. 2008. Wolters Kluwer/Lippincott Williams & Wilkins. Baltimore, MD. 32
Antibacterial agents are either bactericidal or bacteriostatic. Bactericidal drugs attack targets essential for bacterial survival, e.g., inhibitors of cell wall synthesis and most inhibitors of DNA synthesis and integrity.32 Bacteriostatic drugs attack targets that are necessary for bacterial growth but not for survival, e.g., most inhibitors of transcription and translation.32 Since bacteriostatic drugs block bacterial replication, they antagonize the effects of bactericidal drugs.