Transcript Ptotein binding and tissue concentrations

8th ISAP Educational Workshop, Glasgow 2003
Protein binding and
tissue concentrations –
do they matter ?
Ursula Theuretzbacher
Antibiotic Center, Vienna
Tissue penetration - protein binding
Where is the
pathogen?
Where is the
antibiotic?
active serum
concentration
(protein binding!)
•activity (bact., clinical)
•resistance
•colonisation
•toxicity
•other influences
active concentration
at site of infection
Where is the pathogen?
blood capillary
cells
interstitial fluid
Salmonella,
Staph. aureus
Shigella, Listeria
Chlamydia,
Legionella
Site of Infection
Pneumonia
ELF, AM, blood
Bronchitis
bronchial secretions
Sinusitis
sinus secretions
Otitis media
middle ear fluid
Where is the antibiotic?
Eng`s principle of medical procedures:
„The easier it is to do, the harder it is
to change.“
blood capillary
70-80%
homogenates,
biopsies
cells
•intravascular
•extra-, intracellular
20-30%
interstitial fluid
•bound, free fraction
high concentrations
macrolides
fluorquinolones
low concentrations
ß-lactams
aminoglycosides
Site of Infection
Pneumonia
ELF, AM, blood
Bronchitis
bronchial secretions
Sinusitis
sinus secretions
Otitis media
middle ear fluid
Barrier
Where is the pathogen?
Where is the antibiotic?
Protein binding
Tissue penetration
Protein binding
Non-specialized tissues
serum
specialized tissues
Interstitial
fluid
bound
bound
free
drug
equilibrium
• Small reservoirs
• Large reservoirs
free
drug
transport pump
diffusional
barriers
Protein binding
intravascular
determines
distribution
tissue penetration
clearance
interactions
Tissue
cells
interstitial fluid
intracellular
activity!
S Tawara et al. AAC 1992, 36 (1)
extracellular
Protein binding
Methods
•
•
•
•
bioassay
protein precipitation
membrane ultrafiltration
equilibrium dialysis
different methods:
ceftriaxone recovery
from human sera
Species differences
SJ Kohlhepp et al. AAC 1998, 42 (9)
Protein binding: Effect on Penetration of ß-Lactams
% Penetration of total drug (AUC lymph/AUC plasma
into Rabbit Peripheral Lymph
Correlation between protein binding and penetration
100
75
50
25
25
50
Plasma binding %
G Woodnutt et al. AAC 1995, 39 (12)
75
100
Protein binding
g/ml
Cefixime 400mg single dose
5
4
65%
3
2
1
0
0
1
2
3
4
5
6
7
8 h
7
8 h
Cefpodoxime 400mg single dose
5
4
25%
3
2
1
0
0
1
plasma: total
P Liu et al. JAC 2002, 50, Suppl:19
2
3
muscle: free
4
5
6
plasma: calculated free
Protein binding
60
g/ml
50
Cefotaxime 1g iv
serum: total
40
serum free
pleural fluid: total
30
35%
pleural fluid: free
20
10
0
100
0
1
2
0
1
2
90
3
4
5
6
3
4
5
6
Ceftriaxone 1g iv
80
70
60
95%
50
40
30
20
10
0
F Scaglione et al. JAC 1990, 26, Suppl A
h
Protein binding: Moxifloxacin
g/ml
Moxifloxacin:
single p.o. dose of 400 mg
1
52% binding
0,1
2
4
6
8
Total drug: plasma
Free drug: plasma
M Müller et al: AAC1999, 43 (10)
10
12
20
30
40 h
Total drug: interstit. fluid
Free drug: interstit. fluid
Protein binding: Ertapenem
Ertapenem, 1g qd
95% binding
T Laethem et al. AAC 2003, 47 (4)
Non-linear kinetics!
Mean fraction unbound
0,16
0,12
0,08
0,04
0
0
100
200
300
Mean total plasma concentration (g/ml)
Majumdar et al. AAC 2002, 46 (11)
Protein binding
Faropenem 300 mg oral, protein binding: 94%
Cilling curves: Streptococcus pneumoniae, MIC 0,25 µg/ml
3,00
log diff cfu/ ml
2,00
1,00
0,00
-1,00
control without albumin
300 mg p.o. without albumin
300 mg p.o. with albumin
6% free, without albumin
-2,00
-3,00
-4,00
0
2
4
6
8
10
12
time (h)
C Fuhst, Bonn, 2002
14
16
18
20
22
24
26
Protein binding
Fusidic acid: 500 mg
tid, orally for 72 h
Cloxacillin: 2 g i.v.,
single dose
60
60
50
50
40
4h
8h
12 h
30
40
30
20
20
10
10
0
0
serum
synovial fluid
Protein binding >90%
MIC in serum  700-fold
Low static ex-vivo activity
E Somekh et al. JAC 1999, 43 (4)
0,5 h
4h
8h
serum
synovial fluid
Protein binding >90%
MIC in serum  3-fold
Good bactericidal ex-vivo
activity
Protein binding
>90%
>70%
Oxacillin, ceftriaxone,
ertapenem,
teicoplanin, daptomycin,
fusidic acid, rifapentine
Cefazolin, rifampicin
>30%
>10%
Penicillin G,
cefixime, cefotaxime,
erythromycin, clarithromycin,
azithromycin, telithromycin
vancomycin, linezolid
Amoxicillin, piperacillin
cefpodoxime, cefuroxime,
ceftazidime, imipenem
ciprofloxacin, levofloxacin,
gatifloxacin, metronidazole
<10%
Meropenem,
aminoglycosides, fosfomycin
What do we know about protein binding?
Free drug is active
Don`t correlate MIC (measured in protein- free
media) with total concentrations
Protein binding influences tissue penetration
Drugs with high protein binding are not
generally less clinically active
Andre
Tissue concentrations
Site of infection
Concentrations at the site of infection
Activity at the site of infection
Clinical outcome
Resistance
Tissue concentration: pulmonary
Azithromycin, pulmonary disposition
500mg, 3 days
total
concentrations
1 0,6 0,06 0
R Danesi et al. JAC 2003, 51 (4)
Tissue concentration: pulmonary
g/ml
1000
Clarithromycin:
2x 500mg, 4 days
100
Azithromycin:
1x 500mg /1x
250mg, 4 days
10
1
4
8
12
24
8
12
24
0,1
0,01
4
Clari: plasma
Azi: ELF
K Rodvold et al. AAC, 1997, 41 (6)
Azi: plasma
Clari: AM
h
Clari: ELF
Azi: AM
Tissue concentration: pulmonary
Telithromycin, pulmonary disposition
800mg once daily, 5 days
90
Total concentrations (g/ml)
80
70
60
2h
8h
24h
48h
50
40
30
20
10
0
1 0,6 0,06 0
Plasma
Muller-Serieys et al. AAC 2001, 45 (11)
ELF
AM
Tissue concentration: middle ear
Acute otitis media, concentrations in middle ear fluid
Ceftibuten: 9mg/kg
Cefixime: 8mg/kg
Azithromycin: 10mg/kg
g/ml
14
cellfree
12
10
4h
12 h
24 h
with
cells
8
6
with
cells
4
2
cellfree
with
cells
0
Ceftibuten
F Scaglione et al. Br J Clin Pharmacol 1999, 47 (3)
Cefixime
Azithromycin
cellfree
Tissue concentration: middle ear
Haemophilus influenzae
amox/clav
cefaclor
Concentration in middle ear
(mean, g/ml)
Bacteriologic eradication
(after 4-5 days of therapy)
9,5
87%
(amoxycillin 25 mg/kg dose, 3h)
(amoxycillin/clavulanic acid
45/6,4mg/kg/day)
5,1
48%
(20mg/kg single dose, 2h)
3,5
azithromycin
MIC
2
s
2
s
47% (39%)
(10mg/kg day 1, 5mg/kg days 2-5)
s: NCCLS susceptible
Placebo!
R Dagan et al: AAC 2000, 44 (1)
R Dagan et al: Pediatr Inf Dis J 2000, 19 (2)
DM. Canafax et al: Pediatr Inf Dis J 1998, 17 (2)
T Eden et al: Scand J Infect Dis 1983, Suppl, 39
JO Klein, CID 1994,19 (5)
0,5 s
Tissue concentrations: resistance
Ciprofloxacin
fold increase in MIC
Selection of resistance
with lower tissue
concentrations
Selection of resistance
depends on

species
 drug exposure (Cmax,
AUC, unbound)
 duration of exposure
 initial pathogen
susceptibility (MIC)
serum conc. (2x 500mg)
serum conc. (2x 750mg)
Thorburn et al. JAC 2001, 48 (1)
blister fluid conc. (2x 500mg)
blister fluid conc. (2x 750mg)
Tissue concentration – does it matter?
Precondition for activity
• Site of infection  location of antibiotic
• Free active drug concentration at the site of
infection
Don`t mix separated pharmacokinetic
compartments (homogenates!)
• Results may be misleading!
Resistance
• Selection pressure of low concentrations at the
site of infection
Whitehead`s rule:
Seek simplicity, and distrust it.
Take home message:
Consider free levels
Distrust tissue homogenates
Enjoy the meeting