Background: To prevent cardiovascular complications, sometimes double and triple therapy with a vitamin K antagonist (VKA), clopidogrel and/or acetylsalicylic acid (ASA) are indicated. These combinations increase the patient's risk of serious bleeding events. Therefore, adherence to clinical guidelines is of the utmost importance when these high-risk therapies are prescribed.
Methods: We performed a retrospective cohort study of 238 cases in a community pharmacy that were treated with a combination of VKA, clopidogrel and/or ASA between January 2006 and December 2009. Hospital records and community pharmacy records were used to obtain the indication(s), the duration of combination therapy, the presence of risk-increasing and risk-decreasing co-medications and any relevant co-morbidities. The cardiologists' attitudes towards the prescribing of antithrombotic combinations and their self-reported adherence to guidelines were assessed by a brief questionnaire.
Results: We found there was no guideline-based indication for 22 of the 146 cases (14%) on ASA plus clopidogrel and 19 of the 82 cases (23%) on VKA plus ASA. Of the 238 cases given antithrombotic combination therapies, 77 (32%) were placed at an additional increased risk of serious gastrointestinal events, yet 43 (56%) of these did not receive adequate gastric protection. Out of the 19 of 60 cardiologists (32%) who responded to our questionnaire; 17 (90%) and 13 (68%) stated that a strict indication is very important when initiating therapy with ASA plus clopidogrel or ASA plus VKA, respectively.
Conclusions: There is room to further develop adherence to guideline-based prescribing of antithrombotic combination therapies and to improve prescription of gastric protection for patients receiving these high-risk combinations.
Keywords: Vitamin K antagonists; acetylsalicylic acid; anti-thrombotic drugs; bleeding risk; clopidogrel; combination therapy; gastric bleeding; guideline adherence.