What are the Natural Penicillins?
Penicillin G and Phenoxymethyl Penicillin (penicillin V)
What are the longer half life Penicillin G
- Procaine penicillin - 6 to 8 hour half life
- Benzathine penicillin 6 day half life
What are the penicillinase resistant(anti staphylococcal) penicillins
- Methicillin- no longer used
- Oxacillin parenternally administered
- Nafcillin parenternally administered
- Cloxacillin Given orally 50% oral availability
- Dicloxacillin " " "
What are the extended range penicillins (used more often for gram negative bacteria) all 1 hour half life
- Ampicilln: Given P or O
- Amoxicillin: given orally 75% oral availability
What does Probenecid do?
Blocks urinary excretion of penicillins.
What 2 penicillins are excreted into the biliary tract?
Ampicillin only partly and Nafcillin mostly
What is the mechanism of action of Penicillins?
- Work best on actively proliferating organisms, they interefere with cell wall synth by:
- Binding receptors on the bacterial cytoplasmic membrane
- Inhibiting transpeptidases that are responsible for cross linking peptidoglycans
- or activation of autolytic enzymes
Mechanisms of microbial resistance to beta lactam antibiotice (penicillins)
- Formation of Beta Lactamases that destroy the drug
- Mutation of penicillin binding targets
Alteration of porins to decrease penetration of the drug.
What are the narrow spectrum penicillins?
- G and V- used to treat :
- Strep Pyo (group A)
- Strep pneumo (if sensitive strain)
- some gram positive anaerobes
- Treponema pallidum
Which penicilins are beta lactamase resistant?
- Nafcillin, Oxacillin, Cloxacillin, and Dicloxacillin
- used to treat sensitive strains of staph aureus and Staph epidermitis
What are the 2 extended range penicillins?
- Ampicillin and Amoxicillin- used to treat:
- E. coli, Proteus mirabilis, Salmonella, Shigella, H influenzae, H. pylori
- Strep pneumo,
- Listeria monocytogenes- all strains sensitive
- Moraxella catarrhalis
- Borellia bergdorfi
What 2 drugs are used to treat pseudomonas and some gram negatives?
Ticarcillin and Piperacillin