But the side effects of aspirin in the high doses in which it is prescribed for stroke treatment are debilitating and sometimes fatal. Aspirin is usually prescribed in doses ranging from 75-325mg daily. Although this is lower than the megadoses of between 1-4g daily not uncommon 15 years ago, it is not without risk.
Dyspepsia (stomach upset, nausea and vomiting) and gastrointestinal hemorrhage can occur in 10-20 per cent of cases (Lancet, May 31, 1980). Even in low doses it can increase the risk of cerebral hemorrhage. This increase is not statistically great in high risk patients, but in the low risk group the increase may be as high as 21 per cent (Drugs and Therapeutics Bulletin, Jan 20, 1994).
There is continuous debate over the optimum duration of aspirin therapy (BMJ, 1994; 308:71-3). Certainly long term use can cause serious side effects. Aspirin may slow blood clotting, but it can also deplete the body of certain essential vitamins and minerals, especially iron. Not surprisingly, one of the effects of long term aspirin therapy is anemia, a condition which can complicate hemorrhagic disorders. Others include ulcers (particularly in elderly persons), liver damage and allergic reactions such as hives, wheezing, tinnitus, chronic catarrh, headache, confusion and, more rarely, hypotension followed by collapse. Asthmatics can die from severe attacks brought on by aspirin consumption. In combination with thrombolytics such as warfarin or heparin it may augment either the risks or the benefits of those agents, depending on which research one chooses to believe.
In addition, recent commentary on the ATC findings suggests that the researchers got it all wrong. Less than a year after the anti platelet research was published, a small review appeared in the BMJ questioning earlier findings (BMJ, 1994; 308:1213-5). Researchers Alexander Cohen, et al, from the Thrombosis Research Institute took a closer look at the Collaboration's figures for the third arm of the trial, which looked at the efficacy of aspirin in reducing venous thrombosis and pulmonary embolism in patients after surgery. They found that not only was some of the ATC arithmetic substantially lacking, but that they had applied their "meta analysis" (the comparison of like research to produce an informed overview) to trials which were not comparable.
The ATC study had also chosen to "skirt" the issue of substantial side effects such as internal bleeding, because in many of the trials analyzed these side effects were not recorded. But as Cohen and colleagues comment, "This information is not optional data for completeness but is absolutely essential to determine risk-benefit ratios, which must always be clearly defined before any general recommendations are made." These problems served to highlight several important issues, including the poor quality of research hitherto published in medical journals regarding stroke, its treatment and prevention, and the superficial, eager beaver way in which practitioners latch on to any research, however inadequate, presented in an authoritative manner.
Not surprisingly, in the same issue the authors of the ATC study defended their position, saying in effect that their data was not intended to recommend aspirin as a wholesale measure; that "treatment recommendations depend on a variety of considerations, of which trial results are only one part"; that it was up to individual physicians to familiarize themselves with all available data and the variety of treatments in current use; and to plead that the best they could do was to rely on whatever research has been produced to date (BMJ, 1995; 309:1215-7).