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CELL WALL ACTIVE ANTIBIOTICS II - PHARM {ST1}

CELL WALL ACTIVE ANTIBIOTICS II - PHARM {ST1} . BY RANJEET RAMAN.

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CELL WALL ACTIVE ANTIBIOTICS II - PHARM {ST1}

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  1. CELL WALL ACTIVE ANTIBIOTICS II - PHARM {ST1} BY RANJEET RAMAN

  2. Problems with Penicillin G include short half-life, instability in gastric acid, inactivation ​by β-lactamases, allergenicity, and poor coverage of Gram- bacteria. The drugs in ​this lecture address these issues, although allergenicity is inescapable with all β-​lactam drugs.

  3. Longer half-life Procaine (IM injection) Benzathine penicillin (IM injection) Stable in gastric acid Penicillin V (oral)

  4. Targeting Gram- bacteria Ampicillin. Kills Gram+ cocci such as Pneumococcus, Streptococcus, Enterococcus. ​Kills some Gram- such as H. influenzae, E. coli, Proteus, and Salmonella. ​Not allergenic.

  5. Amoxicillin. This is 100% orally bioavailable. Not allergenic. Amoxicillin+ Clavulanate (Augmentin). Remember that clavulanate inhibits β-lactamases. ​This combo is active against β-lactamase-producing Gram- bacteria such as ​Staph aureus, Neisseria, and H. influenzae

  6. Anti-Pseudomonas drugs Carboxypenicillins include: Ticarcillin. Very potent against Pseudomonas, Proteus, Streptococci, other Gram- bacteria. ​Demonstrates time-dependent killing. Ticarcillin+ Clavulanate. Effective against β-lactamase-producing Gram- such as Staph ​aureus, Neisseria, H. influenzae, and Bacteroides.

  7. Aminoacylpenicillins include: Piperacillin. Covers everything Ticarcillin does plus Klebsiella, Bacteroides, and some ​enterococci. Piperacillin+Tazobactam. Effective against almost all Gram- bacteria. Used to fight ​serious Gram- infections.

  8. β-lactamase resistant penicillins Methicillin. Causes nephritis so no longer used. “Methicillin-Resistant Staph aureus” ​(MRSA) are bad news. They are not resistant due to a β-lactamase mutation, but rather ​an altered penicillin binding site.

  9. These are resistant to ALL β-lactam antibiotics. Oxacillin. Has replaced methicillin as the choice for β-lactamase-resistant β-lactam drug. ​Effective against Staphylococci, Pneumococci, Group A Strep.

  10. CEPHALOSPORINS These are also β-lactam drugs but have very broad spectrum coverage, including Gram+, ​Gram-, and Pseudomonas. Three generations of cephalosporins.

  11. Cephalosporins have a post-antibiotic effect (PAE) and time-dependent killing against ​Gram+ bacteria. Continuous infusions are more efficient. Cefotetan. Cefepime. Can kill Pseudomonas. Ceftriaxone. Long half-life. Adverse reactions include hypersensitivity reactions

  12. CARBAPENEMS These are also β-lactam ring drugs. Main drug to know is Imipenem. Imipenem+Cilastatin. Has a very broad spectrum. Fights Gram+ (including ​Enterococci), Gram- (including Pseudomonas), and anaerobes (including ​Bacteroides).

  13. The renal metabolite of Imipenem is toxic to renal tubules. ​Cilastatin is included to inhibit renal dehydropeptidase I, which creates the ​metabolite.

  14. Aztreonam. This also has good Gram- coverage and no penicillin-like allergenicity.

  15. VANCOMYCIN Mechanism of action is to hydrogen-bond to D-ala/D-ala in cell wall peptidoglycan. This ​blocks transpeptidase and cross-linking is blocked. Vancomycin shows time-dependent killing. Adverse reactions include allergenicity and “red man” flush.

  16. Resistance to vancomycin comes from changing D-ala/D-ala to D-ala/D-lac! Hydrogen-​bonding is not possible after this. E. faecium has become resistant (“VRE”). This ​is bad shit.

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