- 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.
- PENECILLIN DERIVATIVES
- CEPHALOSPORIN DERIVATIVE
- TETRACYCLINE DERIVATIVES
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