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The BetaLactam Antibiotics

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Prevent the final step in the synthesis of the bacterial cell wall ... (at therapeutically attainable levels) PK-PD Parameters. H Derendorf ... – PowerPoint PPT presentation

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Title: The BetaLactam Antibiotics


1
The Beta-Lactam Antibiotics
  • Cell wall active agents
  • Prevent the final step in the synthesis of the
    bacterial cell wall
  • Range from very narrow spectrum to very broad
    spectrum

2
ß-Lactams
3
How do they work?
  • The ß-lactam binds to Penicillin Binding Protein
    (PBP)
  • PBP is unable to crosslink peptidoglycan chains
  • The bacteria is unable to synthesize a stable
    cell wall
  • The bacteria is lysed

4
Peptidoglycan Synthesis
5
PK/PD
  • The ß-lactams are time-dependent killers
  • The effect is directly proportional to the amount
    of TIME the concentration of the antibiotic at
    the site of infection is ABOVE the MIC of the
    organism.
  • The ß-lactams are BACTERIOCIDAL (at
    therapeutically attainable levels)

6
PK-PD Parameters
H Derendorf
7
Concentration dependent vs. time dependent
killing in vitro evaluations
WA Craig
8
So many choices which one to pick?
  • What is the likely organism?
  • Whats its major mode of resistance?
  • Wheres the infection?
  • Whats my local environment?
  • the UNC Hospital antibiogram
  • What does the micro lab say?
  • in vitro sensitivity testing

9
Classification
  • Penicillins
  • Natural penicillins
  • PenG, PenVK, Benzathine Pen, Procaine Pen
  • Aminopenicillins
  • Ampicillin, Amoxicillin
  • Anti-Staph penicillins
  • Oxacillin, Dicloxacillin
  • Anti-Pseudomonal
  • Carboxy Ticarcillin
  • Ureido Piperacillin

10
Classification
  • Cephalosporins
  • 1st Generation
  • Cephalexin, Cefazolin
  • 2nd Generation
  • Cefoxitin, Cefuroxime, Cefotetan
  • 3rd Generation
  • Cefotaxime, Ceftriaxone, Ceftazidime
  • 4th Generation
  • Cefepime

11
Penicillin G
  • Available PO, IM, IV (dosed in units)
  • Drug of Choice (DoC) 2-4 MU IV q4h
  • T. pallidum, N. meningitidis, Group A Strep, and
    Actinomycosis
  • Long-acting forms
  • Procaine PenG (12 hrs)
  • Benzathine Pen (5 days) 2.4 MU IM for syphilis
  • Adverse Reactions other than skin rash
  • Penicillin serum sickness/drug fever
  • Jarisch-Herxheimer reaction (1 and 2 syphilis)
  • Hemolytic anemia, pancytopenia, neutropenia

12
Ampicillin/Amoxicillin
  • Amp (IV, PO) Amox (PO)
  • Spectrum PenG H. flu and some E. coli
  • DoC Listeria monocytogenes and
  • Enterococcus Amp 2g IV q4h
  • Dental Prophylaxis
  • Amox 1 gram PO x 1 prior to appt.
  • Integral in H. pylori regimens
  • ADRs
  • Non-allergic rashes (9) esp. when associated
    with a viral illness (mononucleosis - EBV)
  • Amox better tolerated PO and better absorbed (Amp
    must be taken on empty stomach)

13
Oxacillin
  • IV
  • DoC MSSA, MSSE 2g IV q4h
  • Actually less active against Pen susceptible
    isolates than Pen
  • More active than Vanc vs. MSSA
  • Significant hepatic metabolism
  • No need to dose adjust for renal impairment
  • ADRs
  • Hepatotoxicity (cholestatic hepatitis)
  • Neutropenia
  • Kernicterus in neonates

14
Dicloxicillin
  • Oral
  • NOT equivalent to IV Ox (therapeutically)
  • Poor oral absorption
  • 50 (better on empty stomach)
  • Dose 250-500mg po QID

15
Piperacillin
  • IV
  • DoC Pseudomonas
  • Spectrum most Enterobacteriaceae (E. coli,
    Proteus, Klebsiella, Enterobacter, Serratia,
    Citrobacter, Salmonella and Shigella)
  • Most active penicillin vs. Pseudomonas
  • Often used in combination with Aminoglycoside or
    Cipro/Levofloxacin
  • ADRs
  • Bleeding (platelet dysfunction)
  • Neutropenia/Thrombocytopenia

16
ß-Lactamase Inhibitors
  • How do you evade a ß-lactamase?
  • Use a non-ß-lactam agent
  • Steric Inhibition
  • Penicillins with large side chains
  • Cephalosporins
  • ß-lactam ß-lactamase inhibitors
  • Not all ß-lactamases are inhibitable (!)

17
Clavulanic Acid
  • Augmentin (Amox/Clav) PO
  • Spectrum MSSA and upper respiratory infections
    (S. pneumo, H. flu, M. catarrhalis) and most
    anaerobes
  • Clav is responsible for most of the GI
    side-effects seen with Amox/Clav
  • Variable ratios of Amox/Clav in
    liquids/tabs/chewtabs


18
Sulbactam
  • Unasyn (Amp/Sulbactam)
  • Spectrum Amp most anaerobes many enteric Gm
    (-) rods, OSSA
  • DoC for GNR mixed infection E.coli, Proteus,
    anaerobes when Pseudomonas is not implicated
  • Diabetic foot (once Pseudomonas ruled out)
  • Wound infections
  • Sulbactam alone is very active against
    Acinetobacter spp.

19
Tazobactam
  • Zosyn (Pip/Tazo)
  • THE most broad-spectrum penicillin
  • Tazobactam may improve the activity of
    piperacillin vs. gram-negative rods, including
    anaerobes
  • 4.5g IV q8h 3.375g IV q6h
  • 4.5g IV q6h for Pseudomonas

20
The Cephalosporins (generalized)
Not effective vs. Enterococcus or Listeria
21
Cephalexin/Cefazolin
  • PO/IV
  • Stable vs Staph penicillinase
  • Spectrum MSSA, PSSP, most E. coli, and some
    Klebs
  • DoC surgical prophylaxis, bacterial peritonitis
    in CAPD pts 1 gm in the dwell bag
  • Poor CNS penetration
  • ADRs
  • Positive Coombs test (though, hemolytic anemia
    is rare)
  • Leukopenia

22
Cefuroxime
  • IV/PO
  • Extensive use in pediatrics
  • Spectrum Strep pneumo, Viridans Strep, most H.
    flu, N. meningitidis, OSSA
  • Uses uncomplicated CAP (esp. H. flu),
    alternative Rx for acute OM prophylaxis in
    cardiovascular surgery.

23
Cefotaxime
  • IV
  • Spectrum Strep pneumo, Neisseria spp., most Gram
    (-) enterics, M. catarrhalis and H. flu
    (including ß-lactamase )
  • DoC bacterial meningitis (esp. in peds amp if
    lt 4 weeks), CAP, complicated UTI/pyelonephritis,
    Bacterial Peritonitis

24
Ceftriaxone
  • IV
  • Once daily dosing (95 protein bound long
    half-life)
  • Spectrum Strep. pneumoniae, most
    Enterbacteriaceae,
  • Excretion 50 urine, 50 bile no need to
    adjust for renal insufficiency
  • CSF penetration 5-15 in meningitis, 1.5 with
    out inflammation
  • DoC bacterial meningitis, CAP, Strep. viridans
    endocarditis ( gent)
  • ADRs
  • Cholestasis
  • Elevated bilirubin (displacement)
  • Diarrhea

25
Ceftazidime
  • IV
  • Spectrum Enteric GNR (including Pseudomonas
    some Acinetobacter)
  • No anaerobic activity (same for cefotaxime and
    ceftriaxone)
  • DoC Pseudomonas infections (UTIs, pneumonia,
    meningitis, abdominal).

26
Third Generation Cephs Issues
  • ß-lactamase induction?
  • ESBLs
  • De-repression of chromosomal ß-lactamases
  • Selective pressure for VRE?

27
Cefepime
  • IV
  • NON-Spectrum MRSA, C. diff, Burkholderia,
    Stenotrophomonas, gram-negative anaerobes
  • Stable vs. de-repressed chromosomal ß-lactamases,
    but not ESBL
  • Less ß-lactamase induction than 3rd Cephs
  • DoC HAP, febrile neutropenia

28
Carbapenems
  • Imipenem, Meropenem, Ertapenem
  • Broad-spectrum coverage
  • Gram positive PSSP, MSSA, VSE
  • Gram negative most gram-negative organisms
    (Acinetobacter sp., Pseudomonas sp.)
  • Lack of coverage
  • Ertapenem Pseudomonas sp., Acinetobacter sp.
  • All Stenotrophomonas, Legionella sp., MRSA, VRE

29
Carbapenems
  • Distribution similar to penicillins
  • Excretion renal clearance
  • Adverse reactions
  • Hypersensitivity rash, urticaria,
    cross-reactivity
  • Imipenem seizures (rare)
  • High doses
  • Renal dysfunction
  • Most likely can occur with all carbapenems at
    high doses

30
Carbapenems
  • Resistance
  • Gram negative usually combination of mechanisms
    (Carbapenemase production decreased entry)
  • Imipenem
  • Decreased production of OprD (outer membrane
    protein for carbapenems)
  • Imipenem utilizes OprD gt meropenem, ertapenem
  • Pseudomonas, Enterobacter
  • Susceptible to efflux system in Enterobacter
  • Meropenem substrate for multi-drug efflux
    systems
  • May have increased MIC for meropenem but not
    imipenem
  • All low affinity PBPs

31
Monobactams
  • Monobactams Aztreonam
  • Spectrum ONLY ? Gram negative aerobic bacteria
  • Lack of Coverage
  • Some resistant P. aeruginosa, E. cloacae, and C.
    freundii
  • Acinetobacter sp., Stenotrophomonas sp.
  • Pharmacokinetics
  • Well distributed into tissues, esp. inflamed
    tissues
  • Excretion renal clearance
  • Adverse reactions
  • Skin rash
  • Very low cross-reactivity with Beta-Lactam class
    highest risk in patient allergic to ceftazidime.

32
What about penicillin allergies?
  • Literature reports a ceph/pen cross-reactivity of
    1 10
  • The cross-reactivity of aztreonam/pen or ceph is
    essentially 0
  • The cross-reactivity of carbapenems/penicillins
    is also around 5 (similar to that of ceph/pen)
  • Decision making
  • Severity of reaction
  • Reliability or documentation of the history
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