1. Pharmacodynamics of Antimicrobials in Animal Models William A. Craig, M.D. University of Wisconsin-Madison

2. 0246 2 4 6 8 18.8 mg/kg 4.7 mg/kg 1.17 mg/kg 0246 40 mg/kg 10 mg/kg 2.5 mg/kg 0246 40 mg/kg 10 mg/kg 2.5 mg/kg CFU = colony-forming unit. Craig WA, et al. 40th ICAAC Toronto, Ontario, September 17-20, 2000. TelithromycinAzithromycinClarithromycin Time (hours) Log 10 CFU per Thigh Effect of Increasing Concentrations on Killing of Pneumococci in Thighs of Neutropenic Mice

3. In Vivo PAE for Azithromycin with Streptococcus pneumoniae ATCC 10813 in Thighs of Neutropenic Mice

4. Patterns of Antimicrobial Activity  Concentration-dependent killing and prolonged persistent effects  Seen with aminoglycosides, quinolones, daptomycin, ketolides, amphotericin B and echinocandins  Goal of dosing regimen: maximize concentrations  AUC/MIC and Peak/MIC major parameters correlating with efficacy

5. Patterns of Antimicrobial Activity  Time-dependent killing and minimal or no persistent effects  Seen with all beta-lactams and flucytosine  Goal of dosing regimen: optimize duration of exposure  Time above MIC major parameter correlating with efficacy

6. Patterns of Antimicrobial Activity  Time-dependent killing and moderate to prolonged persistent effects  Seen with macrolides, azithromycin, clindamycin, tetracyclines, oxazolidinones, streptogramins, glycopeptides and azoles  Goal of dosing regimen: optimize amount of drug  AUC/MIC major parameter correlating with efficacy

7. Cyclophosphamide 150 and 100 mg/kg at 4 and 1 day before infection Thigh infection produced by injection of 0.1 ml of 10 7 CFU/ml 2 hrs before treatment Lung infection produced by 45 min aerosol of 10 9 CFU/ml 14 hrs before treatment 10 7-8 CFU/g in thigh or lung at start of therapy Neutropenic Murine Thigh and Lung Infection Models

8. Use neutropenic murine thigh-and lung-infection models Evaluate 20-30 different dosing regimens (5 different total doses given at 4-6 different dosing intervals) Measure efficacy from change in Log 10 CFU per thigh or lung at the end of 24 hours of therapy Correlate efficacy with various pharmacodynamic parameters (Time above MIC, peak/MIC, 24-Hr AUC/MIC) Correlation of Pharmacodynamic Parameters with Efficacy

9. Correlation of PK/PD Parameters with Efficacy of Temafloxacin against Streptococcus pneumoniae in Thighs of Neutropenic Mice Craig in Antimicrobial Pharmacodynamics in Theory and Clinical Practice, p 1, 2002

10. Correlation of PK/PD Parameters and Efficacy for Ceftazidime against Klebsiella pneumoniae in a Murine Pneumonia Model Craig in Antimicrobial Pharmacodynamics in Theory and Clinical Practice, p 1, 2002

11. PK/PD Parameters Does the magnitude of the parameter vary markedly with: 1. different animal species 2. the dosing regimen? 3. different drugs within the same class? 4. different organisms ? 5. different sites of infection (e.g. blood, lung, peritoneum, soft tissue)? 6. the presence of neutrophils?

12. Mathematical Analysis of Dose-Response Data from Animal Models after 24 Hours of Therapy Nonlinear regression and Hill equation to estimate Emax (difference from untreated control), P 50 (dose giving 50% of Emax) and slope (N) of the dose-response relationship  CFU= (Emax) Dose N Dose N + P 50 N

13. PK/PD Parameters:  -Lactams  Time above MIC is the important parameter determining efficacy of the  -Lactams  T>MIC required for static dose vary from 25-40% of dosing interval for penicillins and cephalosporins to 10-25% for carbapenems  Free drug levels of penicillins and cephalosporins need to exceed the MIC for 40-50% of the dosing interval to produce maximum survival

14. Drug q1-2 h q3-4h q6-8h q12-24h Cephalosporins 53 ± 20 43 ± 15 42 ± 14 35 ± 11 Penicillins 29 ± 10 31 ± 14 34 ± 16 31 ± 12 Carbapenem 20 ± 4 26 ± 10 23 ± 6 20 ± 4 Craig et al 33rd ICAAC, 1993 (Abstract 86) Time Above MIC Required for a Static Effect After 24-hrs of Therapy with Three ß-Lactam Classes Time Above MIC (Percent of Dosing Interval)

15. Drug Enterobacteriaceae S. pneumoniae S.aureus Ceftazidime 36 (27-42) 39 (35-42) 20,25 Cefepime 35 (29-40) 37 (33-39) 21,24 Cefotaxime 38 (36-40) 38 (36-40) 22,25 Ceftriaxone (T) 62 (56-69) 64 (59-68) 46,69 Ceftriaxone (F) 38 (34-42) 39 (37-41) 24,26 Time Above MIC Required for a Bacteriostatic Effect with Four Cephalosporins Time Above MIC (% of Dosing Interval)

16. Relationship Between MIC and T>MIC for the Static Dose for Cefpodoxime and Cefditoren with Various Strains of S. pneumoniae Urban et al. 19th ICC 1995 (Abstract 2229); Craig, Andes 40 th ICAAC (Abstract 2248) ;

17. Literature Review for T>MIC for Beta-Lactams Versus Mortality in Animal Models At least 48 hrs of treatment Mortality 80-100% in untreated controls Pharmacokinetics provided to calculate magnitude of PK/PD parameter Mortality recorded within 24 hrs after last dose of drug Data from 3 animal species and 4 sites of infection Craig CID 26:1, 1998; Nicolau et al. AAC 44:1291, 2000

18. Relationship Between T>MIC and Bacterial Eradication with Beta-Lactams in Otitis Media (Circles) and Maxillary Sinusitis (Squares)  Bacteriologic cure for different ß-lactams with S. pneumoniae and H. influenzae from double tap studies in acute otitis media and acute maxillary sinusitis  Time above MIC calculated from serum levels and MICs for different organisms Craig & Andes, Pediatr Infect Dis J 15:255, 1996; Dagan et al JAC 47:129, 2001;Dagan et al Pediatr Infect Dis J 20:829, 2001

19. PK/PD Paramters with Fluoroquinolones 24-hr AUC/MIC is the parameter that best predicts activity of fluoroquinolones. 24-hr AUC/MIC (using free drug levels) for static dose range from 25-50 for most organisms in neutropenic mice

20. 24-Hr AUC/MIC with Total and Free Drug for the Static Dose of Different Fluoroquinolones with S. pneumoniae ATCC 10813 Andes & Craig 40th and 41st ICAAC, 2000 and 2001

21. Pharmacodynamics of Fluoroquinolones  Magnitude of 24-Hr AUC/MIC in serum required for 90-100% survival in animal infection models varies from about 25 in immunocompentent animals for Streptococcus pneumoniae to about 100 in immunocompromised animals for gram- negative bacilli  24-Hr AUC/MIC values of 25 and 100 are equivalent to averaging one and four times the MIC over a 24-hr period

22. Relationship Between 24 Hr AUC/MIC and Mortality in Animals for Fluoroquinolones against Gram-Negative Bacilli Andes & Craig, Int J of Antimicrob Agents 19:259, 2002

23. Comparison of Relationships Between 24-Hr AUC/MIC and Efficacy against Pneumococci for Fluoroquinolones in Animals and Patients 58 patients enrolled in a comparative trial of levofloxacin vs gatifloxacin Free-drug 24-hr AUC/MIC <33.7, the probability of a microbiologic cure was 64% Free-drug 24-hr AUC/MIC >33.7, the probability of a microbiologic cure was 100% Animals - Literature ReviewPatients with CAP and AECB Andes & Craig, Int J of Antimicrob Agents 19:259, 2002 Ambrose et al AAC 45:2793, 2001

24. Impact of Dosing Interval on Static Dose for Amikacin against K. Pneumoniae and E. coli in Mice with Normal and Impaired Renal Function Reddington and Craig, JAC 1995

25. Impact of Dosing Frequency on Static Dose for Macrolides and Azalides with Streptococcus pneumoniae ATCC 10813 Drug

26. 24-Hr AUC/MIC with Total and Free Drug for the Static Dose of Different Macrolides, Ketolides and Clindamycin with S. pneumoniae ATCC 10813 Craig et al. 42nd ICAAC, 2002

27. Animal Models for Susceptibility Breakpoint Determinations Simulate human pharmacokinetics in animals (induce renal impairment with uranyl nitrate) Infect groups of animals with organisms with varying MICs Treat the animals for at least 24 hours with dosage regimen used to treat human infections Find the MIC value that separates bacterial killing from bacterial growth

28. Effect of Amoxicillin (7 mg/kg) on 17 Strains of S. pneumoniae in Thighs of Neutropenic Mice

29. PK/PD Parameters Does the magnitude of the parameter vary markedly with: 1. different animal species NO 2. the dosing regimen? NO 3. different drugs within the same class? NO providing free drug levels are used 4. different organisms ? Some (S. aureus-ß-lactams) 5. different sites of infection (e.g. blood, lung, peritoneum, soft tissue)? NO 6. the presence of neutrophils? YES, some drugs more than others