A NEW study that shows a significantly higher risk of heart attack if patients stop taking aspirin has reinforced the need for medication adherence strategies in general practice, an Australian expert on the primary prevention of cardiovascular disease says.
Professor Mark Nelson, chair of general practice at the University of Tasmania, said for secondary prevention of cardiovascular disease, the evidence for low-dose aspirin was level one.
The research, published in the BMJ, analysed data on 39 513 primary care patients aged 50-84 years, with a history of ischaemic cardiac or cerebral events, who were prescribed low-dose aspirin (75-300mg/day). (1)
Over an average follow-up of 3.2 years, those who had recently discontinued aspirin faced a 43% higher risk than those who continued it, of either having a non-fatal myocardial infarction or dying from coronary heart disease.
The risk of myocardial infarction alone increased by 63% in those who stopped taking aspirin. This equated to four extra myocardial infarctions per year for every 1000 patients who stopped taking aspirin.
This is the first study to examine the effects of aspirin discontinuation in a primary care setting.
Professor Nelson said the best strategy to identify patients who were not taking their aspirin was simply to ask. With other medications, physical assessments could indicate compliance, such as pulse rate for patients taking beta blockers.
“But there is no objective measure of compliance for aspirin …. You just have to ask”, he said.
Previous research led by Professor Nelson found that a simple four-item questionnaire on adherence to blood pressure medication identified patients who were more likely to experience a cardiovascular event or death. (2)
Professor Nelson said doctors needed to educate patients about their disease and the benefits of each specific treatment. “You have to take the patient with you”, he said.
He also emphasised the need to explain any common side effects of medication, and the usually transient nature of these. “If patients experience any unexpected side effects, that’s when they are more likely to stop taking their treatment”, he said.
Professor Nelson said strategies such as a dose box or Webster-Pak could assist patients on multiple medications.
The BMJ research examined patients who, like most UK patients taking aspirin for secondary prevention, obtained their medication using a prescription.
Professor Nelson said most Australian patients obtained aspirin over the counter, which could have both advantages and disadvantages for compliance.
“For instance, the morning-after pill went over-the-counter so it was more effective … prescriptions can be a barrier to compliance.”
A related editorial in the BMJ said the research showed that “any day off aspirin is a day at risk for patients with previous cardiovascular disease”. (3)
“Patients on chronic low dose aspirin for secondary prevention of cardiovascular disease should be advised that unless severe bleeding ensues or an informed colleague explicitly says so, aspirin should never be discontinued”, the editorial said.
As with any observational study, the association between aspirin discontinuation and myocardial infarction may have been confounded, Professor Nelson cautioned.
“People may well have gone off the medication because it was futile, for example, if they were nearing the end of their life”, he said.
– Sophie McNamara
Posted 25 July 2011