Quartz 5

Etiotropic Agents

2 min read

Etiotropic Agents = Chemotherapeutic drugs: Target a pathogen
They must be differentiated from Organotropic Agents which targets a receptor, enzyme, protein… that is normally found in the tissue of the treated animal

Drugs:

Concept of Selective Toxicity by Paul Ehrlich:
A drug working like a “magic bullet” that would target the pathogen while remaining harmless to the treated animal

Selective toxicity targets:

  • Unique targets: Drug targets compound only found in the pathogen > Higher Therapeutic Index
    • Inhibition of bacterial cell wall synthesis:
    • Disruption of fungal cell membrane components:
    • Folic acid synthesis pathway inhibitors:
      • Sulfonamides are structural analogues of PABA: they target and block Dihydropteroate synthetase (found in bacteria) that turns PABA into Dihydrofolic Acid DHF
  • Similar targets: Drug targets mostly compound found in the pathogen, but also targets (to a smaller extent) a similar compound found in the animal > Medium Therapeutic Index
    • Folic acid synthesis pathway inhibitors:
      • Trimethoprim (Diaminopyrimidines) targets and blocks Dihydrofolate reductase that turns Dihydrofolic Acid DHF into Tetrahydrofolic Acid THF
        • It has a 400x stronger affinity to bacterial DHF reductase than human’s
    • Protein synthesis inhibitors:
      • Amphenicols target the 50S subunit of the bacterial ribosome with dose dependent toxicity on the human’s ribosome
  • Common targets: Drug targets compound found both in the animal and the pathogen > Lower Therapeutic Index

Graph View

Backlinks