The study analysed 124 patients who had undergone coronary artery stent implantation. All received aspirin 75mg each day, clopidogrel as a loading dose followed by 75mg each day. They were also randomly assigned to either omeprazole 20mg each day or placebo.
The study assessed platelet reactivity index (PRI) on day one and day seven of the study. On day one PRI was 83.2% in the placebo group and 83.9% in the omeprazole group; this was not statistically significant. By day seven PRI was 39.8% in the placebo group and 51.4% in the omeprazole (p<0.0001).
The authors conclude that, "omeprazole significantly decreased clopidogrel inhibitory effect". They also state that the clinical impact of these results is uncertain and requires further investigation.
This study has raised several questions:
- Is this interaction clinically significant, does it increase the risk of further cardiovascular events
- Should omeprazole be avoided in patients taking clopidogrel?
- Does this interaction apply to all Proton Pump Inhibitors (PPIs)?
Action: Clinicians may want to consider avoiding PPIs in patients on clopidogrel wherever possible until the clinical impact of this study becomes clearer.