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Warning over aspirin dose in clopidogrel patients

By Lilian Anekwe

GPs have been advised to apply a 100mg cap on daily aspirin doses prescribed to patients on clopidogrel, after new research found higher doses had no benefits and might even raise the risk of heart attacks and strokes.

The new study of nearly 16,000 patients in the US – where patients on clopidogrel are commonly prescribed aspirin doses up to 325mg daily – suggests the risks of higher hoses are likely to outweigh the benefits.

The overall risk of cardiovascular events was the same in patients prescribed a daily dose of aspirin of either less than 100mg, 100mg, or more than 100mg in addition to clopidogrel or placebo.

But patients on higher aspirin doses alongside clopidogrel had significantly greater rates of myocardial infarction, stroke or cardiovascular death than those on less than 100mg of aspirin, – at 14.5% versus 7.4%.

The study, published last week in the Annals of Internal Medicine, failed to find any subgroup that benefitted from higher doses. There was no difference in rates of gastrointestinal events.

Study leader Dr Steven Steinhubl, director of cardiovascular research at the Medicines Company in Zurich, said a dose of between 75 and 81mg daily provided close to optimum efficacy and safety: ‘This may be especially true in patients receiving dual antiplatelet therapy,' he said.

Dr Mark Aley, a GP in Eastleigh, Hampshire, said: ‘There is some debate that if you push up the dose too much pathways for anticoagulation may be inhibited, so you may do more harm than good. If you can't prove higher doses are doing more good than harm stick to the lowest dose.'

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