1. Interactions with Other Medications and Platelet Turnover
Insights into Factors Affecting Responsiveness to Aspirin and Clopidogrel:
Interactions with Other Medications and Platelet Turnover
Paul A. Gurbel Sinai Center for Thrombosis Research Baltimore, Maryland, USA

2. Disclosures Honoraria/Consulting Research Grants/Support Pozen Pozen
Astra Zeneca
Nanosphere
Accumetrics
Helena
Multiplate
Portola
Daiichi
Honoraria/Consulting
Pozen
Novartis
Bayer
Astra Zeneca
Eli Lilly
Accumetrics
Nanosphere
Sanofi Aventis
Boehringer
Merck
Medtronic 2

3. Drug-Drug Interactions: Oral Antiplatelet Therapy
Aspirin
NSAID’s
Clopidogrel
Proton Pump Inhibitors
Smoking
Calcium Channel Blockers
Lipophilic Statins
St. John’s Wort
Rifampin
Caffeine

4. Aspirin, NSAID’s and Platelet Function
ASA acetylation site
Converts AA to PGG2/PGH2
Ibuprofen reversibly blocks access of ASA to acetylation site
Catella-Lawson et al. N Engl J Med 2001;345:

5. Aspirin, NSAID’s and Platelet Function
- 400mg ibuprofen 2 h before mg ASA - same drugs in reverse order
- 25mg rofecoxib 2h before 81mg ASA - same drugs in reverse order
No effect of acetaminophen or
diclofenac
Catella-Lawson et al. N Engl J Med 2001;345:

6. Clopidogrel Response Variability: A PK Problem
Intestinal Absorption
Esterases 90%
P-glycoprotein -PPI ? ?
Limited absorption
Two Step Conversion
Hepatic P450
Cytochromes
10%
2C19, 1A2, B6
-PPI
+Smoking
Drug-Drug Interactions
- Statin, -Ca+2 Antagonists
+ SJW, -PPI
2C19, 2C9, 3A4, 2B6
Variable Active Metabolite Generation
+ Caffeine via PDE inhibition
Wide Pharmacodynamic Response, Nonresponsiveness
Worse Clinical Outcome
Adapted from Kauzi M et al. Drug Metab Dispos. 2009; Gurbel et al. J Inv Cardiol. 2009 6

7. CYP3A4: Clopidogrel - Atorvastatin/Rifampin Interaction
CYP 3A4 Activity Directly Associated with Post-Clopidogrel Platelet Aggregation
Before 300mg Clopidogrel Load
After 300mg Clopidogrel Load
Atorvastatin Dose
Atorvastatin Increases Post-Clopidogrel Platelet Aggregation
Baseline
Clopidogrel
Clopidogrel +
Rifampin
Rifampin Reduces Post-Clopidogrel Platelet Aggregation
Lau W et al. Circulation 2003;107:32

8. CYP3A4: Clopidogrel - SJW Interaction
120
Clopidogrel 97 95
100
Clopidogrel + St. John's wort 300 mg TID 84 84 79 80 64
Platelet aggregation (%) 60 51 46 40 20
Baseline
2 hr
4 hr
6 hr
Lau WC, Gurbel PA. Et al. J Cardiovasc Pharmacol. 2011;57:86-93 8

9. PDE Inhibition: Clopidogrel – Caffeine Interaction
20 Healthy Volunteers
- 300mg CLP
- 300mg caffeine 30 min after 300mg CLP
5 M ADP-Induced Aggregation
p=0.02
Platelet Activation Markers
Plasma cAMP Levels (fmol)
Baseline
2.5 hrs post-caffeine
40 CAD Patients Post-PCI
>1 wk mg ASA and 75mg CLP
- 300mg caffeine
p=0.01
p=0.02
Lev E et al. Am Heart J 2007:154;694.e1-694.e7

10. CYP2C19:Clopidogrel-PPI Interaction
Gilard et al. J Am Coll Cardiol 2008;51:256-60
n=124 PCI patients
Clopidogrel (300/600 mg LD and 75mg qd) +/- omeprazole for 7 d
Omeprazole
Control
O’Donoghue ML et al. Lancet 2009;374:898-97
n=201 PCI patients
600mg Clopidogrel/ 60mg Prasugrel +/- PPI’s
PRINCIPLE TIMI 44
Prasugrel
Clopidogrel
Adjusted p - value
IN CLP and PRA Pts Treated with PPI at 15 d:
LESS IPA (CLP + PPI, p =0.06; PRA + PPI, p=0.01) 10 10

11. CYP2C19: Clopidogrel–PPI Interaction
PRI-VASP-P
Prevalence of Non-Responders
Cuisset T et al. J Am Coll Cardiol 2009;54:1149–53
Ho MP et al. JAMA 2009;30:
Clopidogrel Without PPI
Clopidogrel With PPI
Death or Rehosp. for ACS
Rehosp. for ACS
Revascl. for ACS
All Cause Mortality
OR=1.25
OR=1.86
OR=1.49
Patients (%)
n = 8205
3-Year Clinical Outcome
OR=0.91 11

12. ACS (STEMI or UA/NSTEMI) ACS (STEMI or UA/NSTEMI)
Influence of PPI’s on Clinical Outcome in Patients Treated with Thienopyridine
O’Donoghue ML et al. Lancet 2009;374:898-97
n=13,608 with ACS
Clopidogrel/ Prasugrel +/-PPI
Bhatt DL et al. N Engl J Med. 2010;363:
n= 3627
Clopidogrel + Omeprazole combo pill vs. Clopidogrel
ACS (STEMI or UA/NSTEMI)
ACS (STEMI or UA/NSTEMI)
TRITON TIMI 38
COGENT Trial
VERY IMPORTANT CAVEAT: NO SIGNIFICANT PLATELET FUNCTION MEASUREMENTS
IN EITHER STUDY 12 12

13. THE SPACING STUDY
P2Y12 antagonists
Gurbel PA et al AHA 2010

14. Change in Platelet Reactivity by VerifyNow P2Y12 Assay
PA Clopidogrel Interaction
Change in Platelet Reactivity by VerifyNow P2Y12 Assay
p<0.001
p<0.001
PRU 65
130
195
260
24 h Post-Load
Day 7
p=0.048
p=0.003 *
ECASA+C
PA32540+C-S
PA32540+C
* p= PA32540+C-S vs. PA32540+C
Gurbel PA et al AHA 2010 14 14

15. 5 uM ADP-Induced Aggregation (%)
CYP3A4:Clopidogrel- Ca++ Channel Blockers Interaction
Siller-Matula et al. J Am Coll Cardiol 2008;52:1557–63
LTA-ADP
VASP-P
P = 0.001
p=0.046
CYP1A2:Clopidogrel-Smoking Interaction
100 90 80 70 60 50 40 30 20 10 NS
(< ½ pack) CS
(> ½ pack)
(n=72)
(n=11) (n=37)
p<0.05
5 uM ADP-Induced Aggregation (%)
20 uM ADP-Induced
Aggregation (%) *
(n=11) (n=37)
Bliden KP et al. J Am Coll Cardiol 2008;52:531–3 15

16. CYP1A2: Smoking - Clopidogrel Interaction
CHARISMA Trial: Berger J et al. Circulation 2009;120:
All Cause and CV Death
Bleeding
CLARITY-TIMI 28 STUDY: Desai NR et al. J Am Coll Cardiol 2009;53:1273–8

17. Platelet Turnover and Antiplatelet Drug Response Variability:
The 2 Platelet Pools Hypothesis
Explanation for Differences In Antithrombotic Properties of Thienopyridines Versus Direct Acting P2Y12 Inhibitors
~ 10 % new platelets enter circulation each day
Thienopyridine Metabolite Exposure (hours )
Exposure of circulating platelets to active thienopyridine metabolite is transient 2 24
As new platelets enter the circulation in the absence of circulating active thienopyridine metabolite they are not inhibited:
young
old
blocked
2 platelet pools

18. Platelet Turnover and Antiplatelet Drug Response Variability:
The 2 Platelet Pools Hypothesis
Explanation for Differences In Antithrombotic Properties of Thienopyridines Versus Direct Acting P2Y12 Inhibitors
Direct acting P2Y12 inhibitors provide uniform platelet inhibition dependent on drug plasma concentration:
1 Pool of Uniformly Inhibited Platelets
blocked

19. Platelet Turnover and Antiplatelet Drug Response Variability:
The 2 Platelet Pools Hypothesis
Platelet turnover increased in ACS and Metabolic syndrome:
Vadagunathan M et al. Am Heart J 2008;1546:1002.e e7
Control UA NSTEMI STEMI
Lakkis N et al. J Am Coll Cardiol :
% Reticulated Platelets
Zimmerman N et al. Circulation. 2003;108:
Young platelets have elevated COX-2:
Aspirin insensitive TxA2 biosynthesis in CABG patients

20. Platelet Turnover and Aspirin Responsiveness in CABG
1mM AA-Induced
Aggregation
p<0.05
Days Post-CABG
Days Post-CABG
Platelet COX-1 and COX-2 Expression
Zimmerman N et al. Circulation. 2003;108:

21. Conclusions
Ex vivo measurements of platelet function demonstrate important drug-drug interactions that affect response to clopidogrel.
These interactions occur mainly at the hepatic CYP level, a pathway that metabolizes over half of the drugs prescribed.
Ex vivo measurements of platelet function have been strongly linked to post-PCI ischemic risk.
Physicians should be aware of these PD interactions particularly in patients with prior thrombotic events.
We should not discount the importance of these interactions in the absence of results from adequately powered prospective clinical trials.
Treatment with aspirin and thienopyridines during conditions associated with high platelet turnover are associated with: aspirin insensitive TxA2 generation
blocked and unblocked pools of platelets 21 21 21

22. Influence of PON1 on Clopidogrel Response and Clinical Outcome
PON1 genotype, paraoxonase plasma activity, plasma clopidogrel active metabolite concentration, and platelet inhibition in relation to nonfatal stent thrombosis
No differences in CYP2C9, 2C19,3A4, 3A5, ABCB1 genotypes
Bouman HJ, et al. Nat Med 2011;17:

23. Influence of PON1 on Clopidogrel Response Variability
10%
CYP3A4, CY3A5, CYP2B6, CYP1A2,
CYP1A1, CYP2E1 and CYP2A6
Paraoxonase
Drugs found to increase PON1 activity/expression
Antioxidants found to increase PON1 activity/expression
Costa LG et al. Biochem Pharmacol. 2011;81: