Aspirin Resistance
February 12th, 2008
It is well known that long-term aspirin use reduces the risk of cardiovascular disease and this is mostly due to aspirin’s anti-platelet effect. This means that aspirin is used to prevent blood clots from forming that can lead to a heart attack or stroke. The usual dose prescribed is 75 mg though some doctors favour higher doses such as 150-300 mg daily. Various studies published over the past few years have identified some patients as being ‘aspirin resistant’ which means that aspirin does not have the same effect on their platelets as it has on other patients’. A review of these studies, published in January in the British Medical Journal, and including 2930 patients, hypothesised that patients classified as ‘aspirin resistant’ (about 28% of those studied) were at about a fourfold increased risk of non-fatal and fatal cardiovascular events. The review also revealed that it appeared from the studies that aspirin resistance was less prevalent in men as in women and, although difficult to generalise to the patient population, higher in patients with impaired kidney function. This might explain why aspirin has been found to be less protective in women than in men. In these ‘aspirin resistant’ patients, other platelet inhibitors did not provide any additional benefit.
So how do you find out if you are ‘aspirin resistant’ and how would your doctor know that you should be treated with a larger dose of aspirin to achieve equal anti-clotting efficacy? Unfortunately, there is no agreed way to get reliable measures of aspirin resistance and so there isn’t a standard test available to help identify non responders. So current advice that you should continue to take standard dose recommendations continues whilst for some patients who bleed heavily as a consequence, the risks of treatment must not be underestimated.
