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→Spectrum of Activity
==Spectrum of Activity==
==Spectrum of Activity==
Over the years different sub-groups of Penicillins have been developed; this is because many bacteria have developed '''beta-lactamases''' which will therefore reduce the action of the antiobiotic
e.g. Penicillin sub-families (all have good activity vs. many obligate anaerobic bacteria)
• The first to be discovered, the natural penicillins (benzylpenicillin or Penicillin G) has:
• a narrow spectrum of activity, being active against mainly gram positive organisms
• failing to kill Staphylococcal organisms (gram positives) if they produced beta-lactamase.
• Anti-staphylococcal penicillins (e.g. Cloxacillin) were then produced, still narrow spectrum but resistant to the beta-lactamase produced by Staphylococcal organisms
• Aminopenicillins (e.g. Amoxycillin) were also synthesised to widen the spectrum of action to include many more gram negative organisms than the natural penicillins. The aminopenicillins are still susceptible to hydrolysis by beta-lactamase enzymes.
• Extended spectrum penicillins (e.g. Ticarcillin) have been produced to increase efficacy against some of the most difficult gram negative infections to treat, such as Pseudomonas aeruginosa. These drugs are still susceptible to hydrolysis by beta-lactamase.
• Addition of a beta-lactamase inhibitor (Clavulanic acid) broadens the spectrum of most sub-gps.
==Pharmacokinetic Considerations==
==Pharmacokinetic Considerations==