Information sourced from BMJ:
Aspirin after stroke reduces further events but benefits decline with time, analysis shows
Taking aspirin reduces the risk of recurrent ischaemic stroke by nearly 60% in the six weeks after a transient ischaemic attack (TIA) or ischaemic stroke, but this benefit declines to no effect by 12 weeks, shows a pooled analysis tracking the effect over time.1
The risk of major stroke is very high for only the first few days after a TIA or minor ischaemic stroke, and observational studies have found greater benefit from early medical treatment in the acute phase than in longer term trials.
Researchers pooled the individual patient data from all randomised trials of aspirin versus control after a TIA or ischaemic stroke and looked at the effects on recurrent stroke in the first six weeks, at 6-12 weeks, and at more than 12 weeks after randomisation. They analysed data on 15 778 participants from 12 trials.
The results, published in the Lancet, showed that aspirin reduced the risk of recurrent ischaemic stroke by 58% in the six weeks after a TIA or minor stroke. Just under 1% of patients randomly assigned to aspirin had an ischaemic stroke (84 of 8452), compared with 2% of the control group (175 of 7325) (hazard ratio 0.42 (95% confidence interval 0.32 to 0.55); P<0.001). And disabling or fatal ischaemic stroke was reduced by nearly 70% in people taking aspirin (0.29 (0.20 to 0.42); P<0.001).
Some further reduction in risk of ischaemic stroke accrued in patients who took aspirin when compared with controls at 6-12 weeks, but no benefit was seen after 12 weeks (stroke risk odds ratio 0.97 (0.84 to 1.12); P=0.67).
“The effect of aspirin on risk of early recurrent events has been underestimated,” said the research group, led by Peter Rothwell, of the Stroke Prevention Research Unit at John Radcliffe Hospital in Oxford, UK.
“It is essential that aspirin is given to patients with suspected TIA or minor stroke immediately,” the researchers said. “Medical services should give aspirin as soon as possible and public education should be aimed at self administration after unfamiliar transient neurological symptoms suggestive of threatened stroke.”
In a further analysis, the research group studied the time course of interaction between the effects of aspirin and dipyridamole in the secondary prevention of stroke.
Dipyridamole plus aspirin had no greater effect than aspirin alone in reducing recurrent stroke within 12 weeks (odds ratio 0.90 (0.65 to 1.25); P=0.53). But dipyridamole did significantly reduce stroke risk after that (0.76 (0.63 to 0.92); P=0.005), particularly of disabling or fatal ischaemic stroke (0.64 (0.49 to 0.84); P=0.001).
“Our findings highlight the fact that to understand the effects of newer drugs in comparison to, or in combination with, older drugs, it is first necessary to fully understand the effects of the older drug,” the research group concluded.
01. Rothwell PM, Algra A, Chen Z, et al. Effects of aspirin on risk and severity of early recurrent stroke after transient ischemic [attack] and ischaemic stroke: time-course analysis of randomised trials. Lancet 2016; published online 18 May.
[Free full-text Lancet PDF | PubMed® abstract]
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