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43 Cards in this Set

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Vancomycin, Teicoplanin
1. spectrum of action

1)Bacteriostatic against G+ cocci, bactericidal against G+ rods (including penicillinase producers and methicillin-resistant strains)
NOT effective against G-

used orally to treat AB-resistant pseudomembranous colitis and stapylococcal enterocolitis, and esp. MRSA in pneumonia
2. mechanism of action

2)Binds to D-ala-D-ala terminus of murine monomer and inhibits murine polymer synthesis by blocking attachment of repeating disaccharide units to pre-existing cell wall.
3. pharmacokinetics
4. Distribution
5. Drug interactions

3-5. poorly absorbed from GI. Primarily renal elimination. No cross resistance or cross allergenicity w other antibiotics.
6. Resistance
7. Toxicity and adverse effects

6. Bacteria aquire ability to replace terminal D-ala with D-lactate (van HAX genes)
7. Hypersensitivity, neprhotoxicity, neutropenia, skinflushing or rash "red man syndrome"
Whats different about Teicoplanin? (from vanco)
extended half life, 1X/day dosing. NO/less pain or tissue necrosis after IM injection. Less nephro/oto toxicity
Name the β-lactams
Penicillins, cephalosporins, Carbacepham, Carbapenems, Monobactam
About natural Penicillins...
G and V. From fungus and semisynthetic derivatives. Come closest to the ideal of full antibacterial spectrum with low toxicity, esp some newer derivatives.
Penicillin chemistry
Strong organic acids.
Ionized at physiological pH.
Bc free acids are poorly soluble, they are frequently provided as Na+ or K+ salts.

A 6-aminopenicillanic acide nucleus composed of a thiazoldiline ring fused to a beta-lactam ring
Why is Ring B important?
Ring B is:
1. the active center of the
2. the site of action of bacterial enzymes (βlactamases and penicillinases)
3. the site of formation of the "major" antigenic determinants of the penicillins
Alterations in the R group change what properties of the penicillin molecule?
1. Acid stability
2. Sensitivity to penicillinase activity
3. Antibacterial spectrum
4. Potentcy
1. Spectrum
2. Mechanism (& site) of Action

1. Full spectrum (except when resistant)
2. (Peni/Cephalo)Inhibition of the synthesis of crosslinks between the repeating disaccharide subunits of the bacterial cell wall.
These antibiotics are structural analogues of the D-ala-D-ala substrate for the transpeptidase and form a covalent complex which is inactive.
These ABs bind to PBPs that catalyze or participate ion a variety of rxs necessary for the synthesis &
maintenence of the cell wall.
β Lactam Abs also activate/disinhibit autolytic enzymes which normally fxn to break down the cell wall during cell growth and division.
Penicillin G is absorbed...?
ORALLY. is also ACID-LABILE. oral=max blood levels at 45-60 min, IM= w/i 15 min
Elimination of Penicillin G...?
renal secretion of unmetabloized drug. short serum half life. In renal failure this can increase to 10 hrs; dose must be altered.
Why are liver generated metabolites of Penicillin G important?
Although they lack anitbacterial activity, they are important for generation of hypersensitivity.
How do we maintain blood levels of Penicillin G for extended periods of time?
1) delay absorption from IM sites by adding organic bases such as procaine or benzathine. (penicillin G + benzathine= still tx of choice for syphilis)
2) Administer probenecid- a competitive blocker of tubular secretion of organic acids
What are the 4 mechanism of beta-lactam resistance?
1- ↓ affinity of PBPs through mutation and recombination
2- ↓ cell wall permeability
3- ↑ activity of β lactamases
4- energy dependent efflux pumps
Penicillinase/β-lactamase resistant Penicillins (3)

These resist hydrolysis by exocellular β-lactamases produced by S Aureus and S Epidermis
How does bug become resistant to Methicillin?
Related to failure to bind to PBPs.
Methicillin resistant bugs are likely to be resistant to other penicillins and cephalosporins.
What are the extended range penicillins?
Ampicillin, Amoxicillin
What is the spectrum of extended range penicillins?
They have ↑ spectrum due to better penetration of G- outer membrane and/or decreases the susceptibilityto G- penicillinases.
It IS however MORE susceptible to G+ penicillinases

active against E Coli, P mirabilis, H influenzae, Salmonella, Shigella, Neisseria
What are the anti-pseudomonal Penicillins?
1- Carboxylated derivatives: CARBENICILLIN, TICARICILLIN
2- N-acyl derivatives: PIPERICILLIN
Name the suicide inhibitors of β-lactamases
Clavulinic Acid (clavulanate)
Tazo bactam
Name β-lactamase inhibitor/penicillin combination drugs
Augmentin= Clavulanate + amoxicillin
Timentin= Ticaricillin + clavulanate
Unasyn= ampicillin + sulbactam
Zosyn= Pipericillin + Tazobactam
What are the adverse effects of Penicillins?
CV overload due to salts
inhibition of GABA
Coag defects
allergic rxs (metabolites)
What about testing for Penicillin hypersensitivity?
Skin testing is often used. Challenge with the major determinant (pre-pen) will predict about 95% of IgE-mediated hypersensitivity. soooo, even a neg test doesn't guarantee the absence of an anaphyllactic response
RAST is used to detect penicilloyl-specific IgE ab wo skin testing, results comparable to skin testing.
Whats so speial about the Cephalosporins?
Broad spectrum (even G- bacilli) w a higher degree of resistance to G+ penicillinases.
3rd generation are good for pulmonary, urinary, surgical and bone issues.
What are the major 1rst gen cephalosporins?

Whats thier problem?

Good activity against G+, moderate activity against G-
Not effective against MRSA, not DOC for active infection (No CNS penetration) but may be DOC for surgical prophylaxis
What are the 2nd generation Cephalosporins?
Cefuroxime axetil
Carbacepham (not a true cephalosporin)
What is different about the 2nd gen cephalosporins from the first?
Increased activity against G-, decreased activity against G+
What are the major 3rd generation cephalosporins?
Cefotaxime- G- enterics
Cefpodoxime- UTIs & URIs
Ceftazidime- P Aerug & MDR G-
Ceftriaxone- DOC for N. gonrrhrea & B. Burgdorferei
What is the major 4th generation cephalosporin?
Pseudomonas and G-
better than 3rd gen against G+ due to resistance to chromosomally encoded Beta-lactamases
What are some of the adverse effects of Cephalosporins?
Vit K def (& upset stomach)due to eradication of the GI flora
Allergy in pts allergic to penicillins
What is Locarbef?
Carbacepham- a cephalosporin derivative w activity comparable to that of cefaclor or Augmentin
What are the Carbapenems?
Extremely broad spectrum.
Resistant to B-lactamases.
Given in combination with cilastatin (a dipeptidase inhibitor) as PRIMAXIN to avoid rapid hydrolysis by renal tubule dipeptidase.
Does not require cliastatin to acheive therapeutic concentrations. Less nephrotoxic than imipenem
longer plasma half-life permitting once daily dosing
Excellent activity against G-, poor activity against G+
What are the Lipopeptide antibiotics?

Daptomycin (Cubicin)
What about daptomycin?
Used for tx of complicated skin structure infections by aerobic, G+ organisms.
Bactericidal against vancomycin resistant enterococci.

Injection only
Daptomycin mechanism?
Binds to bacterial membranes and forms membrane channels (in a Ca+ dependent manner) leading to rapid membrane depolarization thus inhibiting protein, RNS and DNA synthesis.
Daptomycin side effects?
irritation at site of injection, skeletal muscle pain and weakness, increase in CPK, renal failure