Background Antiplatelet therapy is a cornerstone for prevention and treatment of cardiovascular atherothrombotic diseases. Low-dose aspirin is usually the first choice antiplatelet drug. Furthermore, aspirin combined with clopidogrel has become the gold standard for patients receiving coronary stent or suffering from acute coronary syndrome. In cases when antiplatelet therapy fails, potential interactions with other concomitant drugs should be considered.

Purpose was to identify possible aspirin and clopidogrel interactions with co-administrated drugs and to work out a recommendation for optimisation of pharmacotherapy.

Materials and methods In this study 70 patients were included from practices of family doctors in Riga who used antiplatelet drugs concomitant with other drugs at the time from July 2010, to January 2011. In the questionnaire such facts from the outpatient cards as sex, age, clinical diagnosis, duration of antiplatelet drug use, dosage and other drugs used were collected. In collaboration with family doctors the information about drug using-habits was summarised.

Results 53% of patients were taking dual antiplatelet therapy (ie, aspirin and clopidogrel combination). The daily dose of clopidogrel was 75 mg. The daily dose of aspirin used frequently was 100 mg (69%). From information collected about concomitant drugs that possibly interact with aspirin prescription, non-steroidal anti-inflammatory drugs (27%) with diclofenac should be noticed as most common (74%) and non-prescription non-steroidal anti-inflammatory drug ibuprofen (25%). Among patients who received dual antiplatelet therapy 59% also used proton pump inhibitors with omeprazole as mostly used (55%) and 38% – statins with atorvastatin as most common (57%). These drugs are stated to have a potential interaction with clopidogrel.

Conclusions Clinicians should probably judge patients taking such combination therapies as aspirin with diclofenac as at high risk of bleeding; also those taking combinations of aspirin and ibuprofen, clopidogrel and omeprazole and/or atorvastatin as a reduced efficacy of antiplatelet therapy.