Proton pump inhibitors and clopidogrel are commonly prescribed medications, both alone and in combination. In January of 2009 the US Food and Drug Administration and the European Medicines Agency issued warnings with regard to the concomitant use of clopidogrel and proton pump inhibitors. Later that year, these warnings were limited to the proton pump inhibitor omeprazole. These warnings were largely based on in-vitro studies and observational analyses suggesting decreased efficacy of clopidogrel in the presence of proton pump inhibitors. Recent literature has suggested there may not be a clinically meaningful interaction.