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Tuesday, 2 March, 1999, 11:51 GMT
Aspirin: A century of good news
As yet more good news about aspirin emerges, BBC News Online examines the history of this "wonderdrug".
This week, it was revealed that aspirin may boost the chances of some lung cancer patients.
There are now more than 50 over-the-counter drugs in which aspirin is the principal active ingredient.
Aspirin is not only an effective painkiller. New benefits of the drug are regularly being discovered.
It is now thought to help fight conditions ranging from cardiovascular disease and cancer to migraine headache and high blood pressure in pregnancy.
Studies have suggested it can double the chances of an IVF pregnancy - and may even block the spread of certain viruses.
The history of aspirin
As far back as the fifth century BC Hippocrates used a bitter powder obtained from willow bark to ease aches and pains and reduce fever.
The willow bark contained salicin, the pharmacological ancestor of a family of drugs called salicylates, of which aspirin is the most famous.
The discovery of aspirin was inspired by Felix Hoffman's attempt to find a drug to ease his father's arthritis without causing the severe stomach irritation associated with the standard anti-arthritis drug of the time, sodium salicylate.
Hoffman was looking for a less acidic formulation. He came up with a compound called acetylsalicylic acid (ASA) which appeared to share the therapeutic properties of other salicylates, without causing stomach irritation.
Hoffman's employers, Friedrich Bayer & Company were concerned that ASA at high doses produced shortness of breath and a rapid heart rate.
They feared - wrongly - that ASA would weaken the heart.
They gave ASA its now familiar name of aspirin, but doubted that it would ever become commercially viable.
What does apirin do and how does it work?
At smaller doses, aspirin interferes with blood clotting.
At higer doses, it reduces fever and eases minor aches and pains.
The way aspirin works is not fully understood.
Most authorities believe it inhibits production of prostaglandins, following pioneering work by Professor Sir John Vane in the 1970s
He received the Nobel prize for medicine in 1982 for his work identifying that aspirin blocked the work of hormone-like substances called prostaglandins.
Prostaglandins are also known to cause redness and fever, common signs of inflammation.
By blocking the synthesis of prostaglandins, aspirin prevents the blood platelets from aggregating at the site of a wound or injury so no blood clot can occur.
Aspirin's role in preventing heart attacks
A heart attack or myocardial infarction (MI) results from the blockage of blood flow not through the heart but to heart muscle.
Without an adequate blood supply, the affected area of muscle dies and the heart's pumping action is either impaired or stopped altogether.
The most common sequence of events leading to an MI begins with the gradual build-up of plaque (atherosclerosis) in the coronary arteries.
Circulation through these narrowed arteries is restricted, often causing the chest pain known as angina pectoris.
Studies have shown that aspirin substantially reduces the risk of death and/or non-fatal heart attacks in patients with a previous MI or unstable angina pectoris, which often occurs before a heart attack.
Aspirin for Healthy People?
There is no conclusive evidence that taking aspirin can prevent a first heart attack in healthy individuals.
A major US study found that healthy men taking aspirin had a substantial reduction in the rate of fatal and non-fatal heart attacks compared with a placebo group.
But there was no significant difference between the aspirin and the placebo groups in the number of strokes, or in overall deaths from cardiovascular disease.
A similar British study found no significant effect from taking aspirin.
Clinical trials have been carried out to test the impact of aspirin on a range of other diseases, including:
None of these uses for aspirin has been shown conclusively to be safe and effective.
There is concern that people may be misusing aspirin on the basis of unproven notions about its effectiveness.
The side effects of aspirin
Even at low doses aspirin is not harmless.
A small number of people are hypersensitive to aspirin and cannot tolerate even small amounts of the drug.
In higher doses aspirin can cause nausea, heartburn and stomach pain.
People being treated for rheumatoid arthritis who take large daily doses of aspirin are especially likely to experience gastrointestinal side effects.
Aspirin's antiplatelet activity apparently accounts for haemorrhagic strokes, caused by bleeding into the brain, in a small but significant percentage of people who use the drug regularly.
For the great majority of occasional aspirin users, internal bleeding is not a problem.
But aspirin may be unsuitable for people with uncontrolled high blood pressure, liver or kidney disease, peptic ulcer or other conditions that might increase the risk of cerebral hemorrhage or other internal bleeding.
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