Proton pump inhibitors should be avoided in patients being treated with clopidogrel. PPIs appear to attenuate the effect of clopidogrel, and there's even some suggestion that the addition of PPIs to the medication regimen of patients taking clopidogrel may be associated with an increased risk of rehospitalization or death.
References
ACC/AHA Focused Update of the 2007 Non-STE-ACS Guidelines (Circulation 2011)
