In the previous post we discussed as to what are the benefits and possible harmful effects of using aspirin (click here). This video describes, how action of aspirin cause these effects.
Long Term Use of Aspirin
Use of aspirin and upper GI bleeding is a common presentation. Thus it's worthwhile looking into benefits and disadvantages of using long term aspirin therapy.
Its parent molecule, salicin, was synthesized from willow bark, it was an old remedy for rheumatism and inflamed joints. Felix Hoffman, trying to spare his arthritic father more heartburn, modified it to acetylsalicylic acid while he was an employee at Bayer. It was the company which trademarked the drug in 1899, and for the next half century, it was used as an analgesic drug.
In 1986, it's vascular benefits were proved and in 1988 a trial in United States confirmed that it can reduce the morbidity associated with ischaemic heart diseases by 44 percent. By 1996 FDA has approved it's use in secondary prevention of vascular events.
There are number of reported beneficial effects of low-dose aspirin.
The risk-benefit trade-off includes major upper gastrointestinal (GI) bleeding. The underlying mechanisms include local mucosal damage, poor cellular repair, and a systemic bleeding tendency. Both a damaged GI mucosa and the haemostatic defect are necessary for GI bleeding to occur.
Aspirin irreversibly inhibits platelet cyclo-oxygenase and the formation of thromboxane-A2, which impairs thromboxane-dependent platelet aggregation. This action is the basis for the beneficial effects of low-dose aspirin and its tendency to cause increased bleeding. The risk of bleeding in a patient on aspirin therapy should be assessed on individual basis, taking other comorbidities into consideration. For example, the attributable risk for hematemesis is 0.2-1.0 per 1000 person-years of exposure, whereas in patients with a history of MI the absolute reduction in vascular events is 40 per 1000 patients treated. Thus there is more benefit in using aspirin that not using, if the patient does not have other comorbidities that would predispose the patient to develop upper GI bleeding.
The number of GI bleeds related to exposure to low-dose aspirin could be minimized by use of several approaches. One is to discourage the indiscriminate use of aspirin since it is not of proven value in the primary prevention of myocardial or cerebral ischaemic events. A second is to ensure that patients take the minimum effective dose. Several studies have shown that the desired benefit can be achieved with doses of 75 mg daily or lower. A third preventive approach might be to advice the use of enteric coated or buffered aspirin. Buffered aspirin is not available everywhere. The cost of 75 mg enteric-coated aspirin is more than 20 times that of 75 mg plain aspirin.
