Biological basis and clinical implications of acetylsalicylic acid resistance.

Acetylsalicylic acid (ASA) is effective in preventing strokes, heart attacks and vascular-related events associated with cardiovascular disease (CVD). Notwithstanding, many patients suffer recurrent events while on ASA therapy. During the past decade, a number of investigators have suggested that these patients are unresponsive to ASA or are 'ASA-resistant'. In the past, this view was met with wide skepticism. Although there is mounting evidence that ASA resistance is a real phenomenon, an understanding of its biological basis and how to measure it is still unclear. The complexity of the problem is discussed below in an attempt to stimulate clinicians and CVD researchers to give serious thought to the ASA resistance problem. It is anticipated that a better understanding of ASA resistance will help us to appreciate its relative importance and its implications in the clinical setting.