Beta Lactam Antibiotics

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Beta Lactam Antibiotics
2011-11-27 18:04:10
Beta Lactam Antibiotics

Beta Lactam Antibiotics
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  1. Standard pencillins
    • Penicillin G - IV
    • Penicillin V - more stable in acid, preferred oral
    • Benzathine Pencillin - IM, syphilis and prevent RF
    • Pharmacokinetics: Penicillin G - large CSF concentration
    • Elimination: Kidney
    • Toxicity: hypersensitivity rxn
  2. Anti-staphylococcal Penicillins
    • Stable to beta-lactamase
    • Nafcillin: Not absorbed in GI tract, metabolized in liver
    • Dicloxacillin Well absorbed in GI tract
    • Use: MSSA
    • Adverse rxn: eosinophilia, neutropenia
  3. Aminopenicillins
    • Increased activity against aerobic gram negative bacilli
    • Ampicillin: Can reach high CSF levels
    • Amoxicillin: Better oral bioavailability
    • Elimination: kidney
    • Clinical: Streptococci, enterococci, L monocytogenes
  4. Antipsuedamonal penicillins
    • Extended spectrum aminopencillins
    • Ticarcillin:
    • Piperacillin
    • IV admin where P Aurigunosum is suspected/confirmed
  5. Beta lactamase inhibitors
    • Combined with antipsuedomonals
    • Contain beta lactam ring that binds beta lactamase, allows other beta lactam to exert effect on bacteria
    • Ampicillin/sulbactam
    • Amoxicillin/clavulanate
  6. Cephalosporins
    • Spectrum of aerobic gram negative bacteria increases across generations
    • Anti-staph spectrum decreases across generations
    • Better against enterobacteriaceae than aminopenicillins
    • Adverse Rxn: 10% cross allergenicity with penicillins, avoid in people with IgE mediated penicillin allergy
    • First generation: Cefazolin, active against strep, staph, and e. coli, prophylaxis in surgery
    • Third generation: Ceftriaxone, cefotaxime; better for enterobacteriaceae, H. Influenzae; reach high CSF concentrations
    • Fourth generation: cefepime, no activity against MRSA, enterococci, listeria, B Fragilis
  7. Carbapenems
    • ImipenemBroadest spectrum of all antibiotics
    • Broken down by renal beta-lactamase which causes nephrotoxicity, co-administered with cilastatin
    • Better penetration and access in gram negative bacteria
    • Resistant to beta lactamases
    • Excreted through Kidney
    • Increase risk of seizures
  8. Monobactams
    • Aztreonam
    • No activity against gram positive bacteria, only gram negative
    • Non-allergenic
  9. Glycopeptides
    • Vancomycin
    • Binds to two alanine residues, sterically hinders peptidoglycan elongation
    • Only gram positive bacteria
    • Resistance: Change in terminal alanine to lactate
    • Not absorbed through GI tract
    • Very high doses to reach CSF
    • Excreted entirely unchanged in urine - anuria increase half life
    • Adverse effects: nephrotoxicity (rare), red neck syndrome caused by rapid infusion
    • Use: beta lactam resistant gram positive infections; MRSA, coagulase negative staph, enterococci, pneumococci; serious infections with stpah, enterococci, streptococci in pts intolerant of beta lactams