Aspirin is an essential drug for the treatment of cardiovascular disease. The standard dose is 75mg per day (much lower than that for inflammation or fever). One of the side-effects of aspirin is a gastric ulcer which can be fatal. To prevent this it is common to use enteric-coated aspirin. This passes through the stomach intact and dissolves in the intestines. This prevents high levels of drug forming in the stomach reducing ulcer formation. Recently there is evidence of high levels of aspirin resistance, ie, patients who appear not to achieve the maximum benefit from aspirin. Clinical studies have shown a significant increase in mortality among these patients.

A recent study that we performed showed that enteric-coated aspirin is not as effective as plain aspirin. This was especially noticeable in heavier volunteers. In fact it appeared that enteric-coated aspirin only delivers 50mg aspirin instead of the full 75 mg. For volunteers resistant to enteric-coated aspirin simply switching them to plain aspirin solved the problem.

We propose to recruit patients on 75 mg enteric aspirin and test them for evidence of poor response to aspirin. Poor responders will then be given 75mg plain aspirin and tested for their response. Those that fail to respond will then receive 150 mg aspirin. If the results of the healthy volunteer study are replicated this would provide a very cheap and effective solution to a serious problem.