Protein binding and tissue concentrations

1
Protein binding and tissue concentrations do
they matter ?
8th ISAP Educational Workshop, Glasgow 2003

• Ursula TheuretzbacherAntibiotic Center, Vienna

2
Tissue penetration - protein binding

• Where is the pathogen?

• Where is the antibiotic?

3
Where is the pathogen?
4
Site of Infection

• Bronchitis
• bronchial secretions

• Sinusitis
• sinus secretions

• Otitis media
• middle ear fluid

5
Where is the antibiotic?
Engs principle of medical proceduresThe
easier it is to do, the harder it is to change.
6
Site of Infection

• Bronchitis
• bronchial secretions

• Sinusitis
• sinus secretions

• Otitis media
• middle ear fluid

7

• Where is the pathogen?
• Where is the antibiotic?

• Protein binding
• Tissue penetration

8
Protein binding

• Small reservoirs
• Large reservoirs

9
Protein binding

• determines
• distribution
• tissue penetration
• clearance
• interactions

10
Protein binding

• Methods
• bioassay
• protein precipitation
• membrane ultrafiltration
• equilibrium dialysis

different methodsceftriaxone recovery from
human sera

• Species differences

SJ Kohlhepp et al. AAC 1998, 42 (9)
11
Protein binding Effect on Penetration of
ß-Lactams into Rabbit Peripheral Lymph
Correlation between protein binding and
penetration
100
75
Penetration of total drug (AUC lymph/AUC plasma
50
25
50
100
25
75
Plasma binding
G Woodnutt et al. AAC 1995, 39 (12)
12
Protein binding
?g/ml
65
h
25
h
P Liu et al. JAC 2002, 50, Suppl19
13
Protein binding
?g/ml
35
95
h
F Scaglione et al. JAC 1990, 26, Suppl A
14
Protein binding Moxifloxacin
?g/ml
Moxifloxacin single p.o. dose of 400 mg
1
52 binding
0,1
2
4
6
8
10
12
20
30
40
h
Total drug plasma
Total drug interstit. fluid
Free drug plasma
Free drug interstit. fluid
M Müller et al AAC1999, 43 (10)
15
Protein binding Ertapenem
Ertapenem, 1g qd
95 binding
T Laethem et al. AAC 2003, 47 (4)
Non-linear kinetics!
0,16
0,12
Mean fraction unbound
0,08
0,04
0
200
100
300
0
Mean total plasma concentration (?g/ml)
Majumdar et al. AAC 2002, 46 (11)
16
Protein binding

• Faropenem 300 mg oral, protein binding 94
• Cilling curves Streptococcus pneumoniae, MIC
  0,25 µg/ml

C Fuhst, Bonn, 2002
17
Protein binding

• Fusidic acid 500 mg tid, orally for 72 h

• Cloxacillin 2 g i.v., single dose

• Protein binding gt90
• MIC in serum ? 3-fold
• Good bactericidal ex-vivo activity

• Protein binding gt90
• MIC in serum ? 700-fold
• Low static ex-vivo activity

E Somekh et al. JAC 1999, 43 (4)
18
Protein binding
gt90 Oxacillin, ceftriaxone, ertapenem,
teicoplanin, daptomycin, fusidic acid,
rifapentine
gt70 Cefazolin, rifampicin
gt30 Penicillin G, cefixime, cefotaxime,erythrom
ycin, clarithromycin, azithromycin,
telithromycinvancomycin, linezolid
gt10 Amoxicillin, piperacillincefpodoxime,
cefuroxime, ceftazidime, imipenemciprofloxacin,
levofloxacin, gatifloxacin, metronidazole
lt10 Meropenem,aminoglycosides, fosfomycin
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What do we know about protein binding?

• Free drug is active
• Dont 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
20
Tissue concentrations

• Site of infection
• Concentrations at the site of infection
• Activity at the site of infection
• Clinical outcome
• Resistance

21
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)
22
Tissue concentration pulmonary
?g/ml
4
8
12
24
h
24
12
8
4
K Rodvold et al. AAC, 1997, 41 (6)
23
Tissue concentration pulmonary

• Telithromycin, pulmonary disposition

Total concentrations (?g/ml)
1
0,6
0,06
0
Muller-Serieys et al. AAC 2001, 45 (11)
24
Tissue concentration middle ear

• Acute otitis media, concentrations in middle ear
  fluid

?g/ml
14
12
10
8
6
4
2
0
F Scaglione et al. Br J Clin Pharmacol 1999, 47
(3)
25
Tissue concentration middle ear

• Haemophilus influenzae

Concentration in middle ear (mean, ?g/ml) Bacteriologic eradication (after 4-5 days of therapy)
9,5 (amoxycillin 25 mg/kg dose, 3h) 87(amoxycillin/clavulanic acid 45/6,4mg/kg/day)
5,1 (20mg/kg single dose, 2h) 48
3,5 (10mg/kg day 1, 5mg/kg days 2-5) 47 (39)
MIC
amox/clav
s
0,5
cefaclor
2
s
azithromycin
2
s
s NCCLS susceptible
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)
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Tissue concentrations resistance
Ciprofloxacin

• 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)

Thorburn et al. JAC 2001, 48 (1)
27
Tissue concentration does it matter?

• Precondition for activity
• Site of infection ? location of antibiotic
• Free active drug concentration at the site of
  infection
• Dont mix separated pharmacokinetic compartments
  (homogenates!)
• Results may be misleading!
• Resistance
• Selection pressure of low concentrations at the
  site of infection

28
Whiteheads ruleSeek simplicity, and distrust
it.

• Take home message
• Consider free levels
• Distrust tissue homogenates
• Enjoy the meeting