DATA BASE

SEMISYNTHETIC ANTIBIOTICS



INTRODUCTION

    1. These are partially modified natural antibiotics in the pharmaceutical laboratory in order to
      • Improve the efficacy of the natural product
      • Reduce its side effects
      • Circumvent developing resistance by the targeted bacteria .
      • Expand the antibiotic spectrum

PHARMACOLOGY OF SEMISYNTHETIC ANTIBIOTICS:

  • The reactive betalactam ring is common to all Penicillins and Cephalosporin C analogues.
  • This ring opens during acylation of the bacterial wall-building enzymes, but previous opening of the ring by acid or beta-lactamases destroys antibiotic activity.
  • Semisynthetic substitutions may protect the ring by steric hindrance;
  • This may actually inactivate certain penicillinases, so that resistant penicillins may potentiate penicillin G in some circumstances.
  • The protective substitutions reduce the intrinsic activity of the synthetic penicillins themselves.
  • Other properties which are affected include absorption, protein-binding, excretion, and possible allergenicity of the drugs.
  • Effects on antibacterial spectrum may possibly be secondary to alteration of lipid solubility.
  1. PENECILLIN DERIVATIVES
  2. CEPHALOSPORIN DERIVATIVE
  3. TETRACYCLINE DERIVATIVES

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