Omeprazole is commonly co-prescribed with
clopidogrel.
Clopidogrel requires bio-activation by
cytochrome P450 CYP2C19.
Omeprazole may reduce
clopidogrel's antithrombotic efficacy by inhibiting
CYP2C19. Studies in Caucasians receiving
omeprazole with
clopidogrel showed no significant increase in death and
myocardial infarction with this drug-drug interaction. There are limited large-scale studies in Asians, who may have a greater prevalence of
CYP2C19 loss-of-function polymorphisms. A single centre retrospective cohort study was undertaken based on a review of medication records and prescription data. Patients prescribed
clopidogrel from 2009 to 2012 were followed-up with until December 2012 (median:29 months). The primary outcome was all-cause mortality and secondary outcomes were
myocardial infarction (MI),
cerebrovascular accidents, and subsequent coronary interventions. Of 12,440 patients prescribed
clopidogrel, 62%(n = 7714) were on
omeprazole (63.8% Chinese, 13.9% Malay, 12.4% Indian, 10.0% others), and 38%(n = 4726) were not on
omeprazole or other
proton pump inhibitors (62.6% Chinese, 13.5% Malay, 10.7% Indian, 13.2% others). Mortality after co-prescription occurred in 14.3%(n = 1101) of patients, compared to 6.3%(n = 300) of patients prescribed
clopidogrel only. Multivariate analysis using propensity score adjusted analysis showed no significant increase in all-cause mortality with co-prescription (adjusted hazards ratio [AHR] 1.13, [95%CI 0.95-1.35]). Patients on co-prescription had a higher risk of subsequent MI (16% vs 3.8%; AHR 2.03 [95%CI 1.70-2.44]), but not of
cerebrovascular accidents (5.0% vs 2.0%; AHR 0.98 [95%CI 0.76-1.27]) or coronary interventions (1.7% vs 0.7%; AHR 1.28 [95%CI 0.83-1.96]). The risk of a subsequent MI was higher in the Malay (AHR 2.43 [95%CI 1.68-3.52]) and Chinese (AHR 2.06 [95%CI 1.63-2.60]) population as compared to the Indian (AHR 1.56 [95%CI 1.06-2.31]) population. In conclusion, the use of
clopidogrel with
omeprazole is associated with an increased risk of MI, but not mortality or
stroke, in this multi-ethnic Asian population. These risks appear to vary among different ethnic groups.