Aspirin
History and Background:
One of the first drugs to be produced and commonly used was aspirin.
However, there is still speculation around it and its side effects therefore
nowadays research still occurs on a large scale with up to 1,000 clinical trials
a year.
From c300 – 1500 BC, an anti inflammatory and pain relieving medicine
known as willow was used. In 1763, an experiment over 5 years showed that
dried, powdered willow bark cured fevers. Over 50 years later, the active
ingredient was extracted from willow; salicin (yellow crystals). In 1853,
Charles Frederic Gerhardt came up with the structure of salicyclic acid and
went on to synthesise acetylsalicylic acid. Just before the 20th Century, Felix
Hoffman and Arthur Eichengrun discovered that by adding an acetyl group to
salicyclic acid, the irritant properties were reduced. Acetylsalicyclic acid is
named Aspirin by Bayer in 1899. In 1974, a clinical trial proved that aspirin in
the secondary prevention from heart attack showed a reduction of mortality by
12% after 6 months and 25% after 12 months. 20,000 patients who suffered
acute ischaemic stroke were part of a study which showed that aspirin
produces a small but positive effect. In 1998, it was determined that aspirin
significantly reduces cardiovascular events in hypertensive patients. In 2011,
eight clinical trials determined that patients who took aspirin daily for four
years have a 44% reduced risk of dying from cancer compared with
participants who took a placebo drug.
Uses:
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Pain relief- lower back and neck pain, flu, burns, menstrual pain,
headache, sprains, toothache, muscle pain
Prevent a heart attack in people who are at a high risk
Prevent a second heart attack or stroke
Reduce the risk of a ‘mini stroke’
Reduce the clotting of platelets for people who need it
Reduce blood clotting for people who have had a hip replacement
Treating cancer/ reducing the risk of cancer
During a heart attack to reduce the risk of dying
Side Effects:
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Heartburn/indigestion
Stomach cramps
Nausea
Signs of bleeding; coughing blood, nose bleeds
Tiredness/Fatigue
Vomiting
Hearing problems
Synthesis:
The synthesis of aspirin goes through 3 steps : synthesis, isolation and
purification and the estimation of purity. The first step is the reaction of
salicyclic acid and acetic anhydride in the presence of a acid catalyst;
phosphoric acid.
Once this reaction is complete, aspirin is put in cold water where it is insoluble
and it is then filtered and isolated. Purification occurs by recrystallization. The
aspirin crystals are then removed by vacuum filtration. Lastly, aspirin and its
purity is identified by its melting point. If the aspirin has a lower melting point
than puer aspirin (136 degrees) then it is either impure or not aspirin. A pure
substance will melt over a range of 1 or 2 degrees celcius.