Cephalosporins Flashcards
Cephalosporin nucleus
beta-lactam ring linked to a dihydrothiazine ring
4 ring then 6 ring with a sulfur in the 6 ring
C3 alterations
change pharmacokinetics
C7 alterations
change spectrum of activity
Cephalosporins MOA:
interfere with transpeptidase PBP which disrupts the cross linking which also weakens cell wall and initiates lytic cycle
Cephalosporins are bactericidal/bacteriostatic
bactericidal
Bactericidal activity of cephalosporins depends on
duration of time that free drug levels exceed MIC
Cephalosporins have the ____ % time> MIC requirement
longest; needs to be 60-70 %
General rule for cephalosporin activity in terms of this order and gram + and gram -
cefazolin 1st cefuroxime 2nd ceftriaxone 3rd cefepime 4th ceftaroline anti MRSA
gram + : activity decreases as you go down but increases for ceftaroline so it has 2 triangles touching each other at the tips where cefepime is
gram - : increase as you go down the list and tapers off at ceftaroline, it looks like a stiletto shaped nail
First generation cephalosporins include:
cefazolin, cephalexin, cefadroxil
Cefazolin oral absorption:
poor IV only
Cefazolin 1/2 life
short but the longest in terms of 1st gen cephalosporins
Cefazolin eliminination
renal
Cephalexin oral absorption
high
Cephalexin 1/2 life
short
Cephalexin elimination
renal
Cefadroxil oral absorption
high
Cefadroxil 1/2 life
short
Cefadroxil elimination
renal
1st Generation tissue penetration
skin
bone/joint
urine
lung-variable
CSF is POOR due to active efflux from BBB
1st Generation spectrum coverage
dark purple: streptococcus, viridans, MSSA/MSSE
dark red: E. coli, klebsiella, p. mirabilis
light red: Neisseria
anaerobes: +/- (just oral)
Important: Cephalosporins do not cover which organism?
enterococcus
1st Generation indications
skin/skin structure infections (MSSA, s. pyogenes/s. agalactiae) UTI (E. coli) surgical prophylaxis (cefazolin)
definitive therapy for MSSA
- endocarditis
- osteomyelitis
Second generation cephalosporins include:
cefprozil, cefaclor, cefuroxime, cefotetan, cefoxitin
Second generation cephalosporins used for respiratory infections:
cefprozil, cefaclor, cefuroxime
Cefprozil oral absorption
high
Cefprozil 1/2 life
short
Cefprozil elimination
35-45 %
Cefaclor oral absorption
high
Cefaclor 1/2 life
short
Cefaclor elimination
70% renal
Cefuroxime oral absorption
52% (axetil)
Cefuroxime 1/2 life
short
Cefuroxime elimination
90% renal
Second generation cephalosporins that are cephamycins
cefotetan and cefoxitin
Cefotetan oral absorption
poor IV only
Cefotetan 1/2 life
longer 3.5 hrs
Cefotetan elimination
75% renal
Cefoxitin oral absorption
poor IV only
Cefoxitin 1/2 life
short
Cefoxitin elimination
80% renal
2nd Generation tissue penetration
skin bone/joint urine respiratory intra-ab
CSF is variable- cefuroxime IV penetrates but is clinicaly inferior to ceftriaxone/cefotaxime for meningitis
2nd Generation spectrum coverage for respiratory
dark purple: streptococcus, s. pneumoniae, viridans, MSSA/MSSE
dark red: h. influenzae, m. catarrhalis, E. coli, klebsiella, p. mirabilis
light red: Neisseria, morganella
anaerobes: +/- (just oral)
2nd Generation spectrum coverage for cephamycins
dark purple: streptococcus, s. pneumoniae, viridans, MSSA/MSSE
dark red: h. influenzae, m. catarrhalis, E. coli, klebsiella, p. mirabilis
light red: Neisseria, morganella
anaerobes: + active against most but some resistance found in b. fragilis
2nd Generation cephalosporin indications
upper and lower respiratory infections
otitis media
UTI
cephamycins:
intra-ab infections
mycobacterial infections (cefoxitin)
surgical prophylaxis
Third Generation cephalosporins include
cefixime, cefdinir, cefpodoxime, ceftriaxone, cefotaxime
Cefixime oral absorption
50% so fair
Cefixime 1/2 life
longer 3-4 hours
Cefixime elimination
35-45% renal
Cefdinir oral absorption
21% poor
Cefdinir 1/2 life
short
Cefdinir elimination
20% renal
Cefpodoxime oral absorption
50% so fair