The Pharmaceutical Journal
Vol 270 No 7237 p258
22 February 2003

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Low-dose and coated aspirin may have a reduced effect in stroke prevention

Patients taking low-dose and enteric coated aspirin to prevent strokes may not be getting the antiplatelet effect they need to avoid such events, a preliminary study indicates.

Researchers from the Northwestern Memorial Hospital, Chicago, Illinois, presented their findings last week at the American Stroke Association conference in Phoenix, Arizona.

They collected data on aspirin dose and formulation type for 254 inpatients and out-patients with cerebrovascular disease, including ischaemic stroke, transient ischaemic attacks and stenosis of a cerebral artery, and measured the resulting antiplatelet effects.

Over half (56 per cent) of patients taking low-dose (81mg) aspirin showed no antiplatelet effect. No effect was seen in 28 per cent of patients in a group taking a 325mg dose.

Comparing enteric coated and non-coated formulations, the researchers found no antiplatelet effect in 65 per cent of patients taking the former presentation, compared with 25 per cent taking the uncoated drug. Other preliminary analyses showed that the antiplatelet effect of aspirin was less effective in older patients and more effective in women than men. "Routine testing of antiplatelet effects may be necessary," suggested Dr Mark Alberts, the study's lead author. He added: "While research has established that aspirin reduces the risk of stroke in patients with cerebrovascular disease, the optimal dose and formulation still remains somewhat unclear. This study is significant in that it points researchers in the right direction — showing how we can maximise the effectiveness of aspirin. ...

"These study results are surprising and unexpected. They have huge public health implications because this could really change how aspirin is given routinely throughout the country, if not the world. This opens the door to the idea that perhaps aspirin should be given as a dose-adjusted medicine."

He cautioned that patients taking aspirin for its antiplatelet effects should not change their dose or stop taking their medication. But he added that it was important to understand that aspirin did not work in everyone.

He encouraged patients to embrace other means of stroke prevention, such as controlling blood pressure and diabetes, stopping smoking, and improving diet and exercise. "Do not rely on taking aspirin alone," he advised.