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Bacterial Metabolism Inhibitors

  • Bacterial Metabolism Inhibitors are a class of antibiotics that target nucleic acids and amino acid synthetic pathways. Historically, this class of antibiotics was one of the first effective pharmacological strategies to treat bacterial infections.
Mechanism of Action
  • Introduction
    • Tetrahydro-folic Acid (TH4) is a key coenzyme for synthesis of nucleic acids and certain amino acids in all life forms. TH4 is synthesized from a precursor, folic acid which in humans is absorbed from the diet. In contrast, bacteria synthesize their own folic acid from the precursor PABA which is the active ingredient in sunscreen.
  • Bacterial Metabolism Inhibitors
    • The Bacterial Metabolism Inhibitors interfere with bacterial TH4 synthesis at two adjacent steps in the pathway. Sulfamethoxazole inhibits the bacterial enzyme which converts PABA into folic acid. Trimethorpim inhibits the bacterial enzyme which converts Folic Acid into TH4. Because these two drugs act on sequential steps of a single pathway their co-administration results in synergistic inhibition of bacterial nucleic acid and amino acid synthesis. Consequently, combined treatment with Trimethoprim plus Sulfamethoxazole "Bactrim" is a potent bacteriostatic therapy.
Adverse Effects
  • Because trimethoprim and sulfamethaxazole are most frequently given in combination, the adverse effects of bactrim are discussed here
  • Dermatitis: Development of skin rash is fairly common
  • Pancytopenia: May occur due to bone marrow suppression, especially in those with AIDS.
Member Drugs
  • Trimethoprim (TMP)
  • Sulfamethoxazole (SMX)
  • Bactrim: Combination of TMP and SMX is the most common compounded form of these drugs