Summary For Antibiotic For USMLE Exam

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Also you should remember this..

+Sulfonamides compete for albumin with:

  • Bilirrubin: given in 2°,3°T, high risk or indirect hyperBb and kernicterus in premies
  • Warfarin: increases toxicity: bleeding

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Beta-lactamase (penicinillase) Suceptible:

  • Natural Penicillins (G, V, F, K)
  • Aminopenicillins (Amoxicillin, Ampicillin)
  • Antipseudomonal Penicillins (Ticarcillin, Piperacillin)

Beta-lactamase (penicinillase) Resistant:

  • Oxacillin, Nafcillin, Dicloxacillin
  • 3°G, 4°G Cephalosporins
  • Carbapenems
  • Monobactams
  • Beta-lactamase inhibitors

* Penicillins enhanced with:

  • Clavulanic acid & Sulbactam (both are suicide inhibitors, they inhibit beta-lactamase)
  • Aminoglycosides (against enterococcus and psedomonas)

Aminoglycosides enhanced with Aztreonam

* Penicillins: renal clearance EXCEPT Oxacillin & Nafcillin (bile)

* Cephalosporines: renal clearance EXCEPT Cefoperazone & Cefrtriaxone (bile)

* Both inhibited by Probenecid during tubular secretion.

* 2°G Cephalosporines: none cross BBB except Cefuroxime

* 3°G Cephalosporines: all cross BBB except Cefoperazone bc is highly highly lipid soluble, so is protein bound in plasma, therefore it doesn’t cross BBB.

* Cephalosporines are “LAME“ bc they  do not cover this organisms

  • L  isteria monocytogenes
  • A  typicals (Mycoplasma, Chlamydia)
  • RSA (except Ceftaroline, 5°G)
  •  nterococci

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* Disulfiram-like effect: Cefotetan Cefoperazone (mnemonic)

* Cefoperanzone: all the exceptions!!!

  • All 3°G cephalosporins cross the BBB except Cefoperazone.
  • All cephalosporins are renal cleared, except Cefoperazone.
  • Disulfiram-like effect

* Against Pseudomonas:

  • 3°G Cef taz idime (taz taz taz taz)
  • 4°G Cefepime, Cefpirome (not available in the USA)
  • Antipseudomonal penicillins
  • Aminoglycosides (synergy with beta-lactams)
  • Aztreonam (pseudomonal sepsis)

* Covers MRSA: Ceftaroline (rhymes w/ Caroline, Caroline the 5°G Ceph), Vancomycin, Daptomycin, Linezolid, Tigecycline.

Covers VRSA: Linezolid, Dalfopristin/Quinupristin

* Aminoglycosides: decrease release of ACh in synapse and act as a Neuromuscular blocker, this is why it enhances effects of muscle relaxants.

* DEMECLOCYCLINE: tetracycline that’s not used as an AB, it is used as tx of SIADH to cause Nephrogenic Diabetes Insipidus (inhibits the V2 receptor in collecting ducts)

* Phototoxicity: Q ue S T  ion?

  • uinolones
  • Sulfonamides
  • T etracyclines

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* p450 inhibitors: Cloramphenicol, Macrolides (except Azithromycin), Sulfonamides

* Macrolides SE: Motilin stimulation, QT prolongation, reversible deafness, eosinophilia, cholestatic hepatitis

Bactericidal: beta-lactams (penicillins, cephalosporins, monobactams, carbapenems), aminoglycosides, fluorquinolones, metronidazole.

* Baceriostatic: tetracyclins, streptogramins, chloramphenicol, lincosamides, oxazolidonones, macrolides, sulfonamides, DHFR inhibitors.

Pseudomembranous colitis: Ampicillin, Amoxicillin, Clindamycin, Lincomycin.

QT prolongation: macrolides, sometimes fluoroquinolones

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