Aspirin, the most widely used antiplatelet therapy, inhibits platelet formation and clopidogrel, a more potent anti-platelet agent, is increasing in usage. However, the recently published MATCH study found the risk of life-threatening and major bleeding was increased by the addition of aspirin in those already receiving clopidogrel [1].

The aim of the present study is to examine the patterns of prescribing of aspirin and clopidogrel in a national prescribing database, and to assess the co-prescribing of anti-peptic ulcer therapies.

The national General Medical Services (GMS) scheme prescribing database was used to identify a cohort of individuals, receiving aspirin alone, clopidogrel alone or both, chronically (3+ months) at anytime from May 2003–April 2004. Individuals receiving any aspirin, or clopidogrel in the previous 4 months (January–April 2003) were excluded as well as those on any anti-peptic ulcer therapy prior to initiating the antiplatelet therapy. Factors including age, gender, any concomitantly prescribed cardiovascular therapies, and subsequent co-prescribing of anti-peptic ulcer therapies were considered in predicting the use of combined vs each antiplatelet therapy alone. Logistic regression was used to calculate adjusted odds ratios (OR) and 95% confidence intervals. SAS Version 8 was used. Significance at p < 0.05 assumed.

The cohort consisted of 65 647 individuals, of whom 58 556 (89%) were receiving chronic aspirin therapy alone, 2650 (4%) clopidogrel alone, and 4441 (6.8%) both therapies. The median duration on therapy was 10 months (IQR 7, 12) for aspirin and clopidogrel alone. The patients receiving clopidogrel alone were significantly more likely to receive anti-peptic ulcer therapies, OR=2.81 (2.59, 3.04), than those on aspirin alone. The patients receiving both antiplatelet therapies were significantly less likely to receive anti-peptic ulcer therapies than those on clopidogrel alone, OR=0.7 (0.63, 0.78), but were more likely OR=1.98 (1.86, 2.11) when compared with aspirin alone. Men were slightly more likely to receive both therapies compared with either aspirin or clopidogrel alone (OR=1.42 (1.33, 1.52) and OR=1.30 (1.17, 1.45) respectively).

1. Diener HC, et al. Lancet 2004; 364: 305.