The clinical significance of using alcohol and aspirin together is uncertain. Complicating factors in studies include:
- the doses selected for each
- the duration of the study
- the proximity of dosing with each substance
- whether other drugs are taken
- whether the participants are healthy volunteers or people with a history of gastrointestinal disorders.
Epidemiological studies have their own shortcomings, such as the participants' candour about their alcohol consumption and their recollections of analgesic use.2
A major epidemiological case-control study based on data collected in the USA and Sweden sought to evaluate whether the deleterious effects of aspirin and other NSAIDs were increased among drinkers.3 The relative risk of acute upper gastrointestinal bleeding was 2.8 times higher for people who consumed at least 21 drinks per week, than for people who consumed less than one drink per week. The relative risk for all current drinkers increased to 7.0 if they were taking more than 325 mg aspirin at least every other day.
A careful analysis of this study agreed that the relative risk of gastrointestinal bleeding due to aspirin, along with an increasing baseline risk with increasing alcohol intake, is consistent with a rising incidence of gastrointestinal bleeding in aspirin users who are heavy drinkers.4 The data supporting an additive effect of aspirin and alcohol on the risks of gastrointestinal bleeding are controversial because:
- the relative risk of taking aspirin did not consistently increase with increasing alcohol use for occasional or regular takers of aspirin or for different doses of aspirin
- while the non-drinking controls had a relative risk of bleeding that was increased from baseline by taking NSAIDs, it did not differ statistically from the risk in patients who combine aspirin and alcohol
- irrespective of the dose, kind or frequency of NSAIDs taken, no significant difference was reported to exist overall between NSAID users who described any current drinking, those who were ex-drinkers, and those who never drank.
There is no proof that mild to moderate alcohol use significantly increases the risk of upper gastrointestinal bleeding in patients taking aspirin, especially if the aspirin is taken only as needed. However, people who consumed at least 3-5 drinks daily and who regularly took more than 325 mg of aspirin did have a high risk of bleeding.