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Aspirin belongs to a group of medicines called non-steroidal anti-inflammatory drugs (NSAIDs). It works by blocking the action of a substance in the body called cyclo-oxygenase.
Cyclo-oxygenase is involved in the production of various chemicals in the body. These are known as prostaglandins, prostacyclins and thromboxane. By blocking the action of cylo-oxygenase, aspirin prevents the production of these chemicals.
High doses of aspirin (300mg and over) prevent the production of prostaglandins. Prostaglandins are produced in response to injury or certain diseases and would otherwise go on to cause pain, swelling and inflammation. Hence a 300mg dose of aspirin is seen as a pain-relieving dose. Alka rapid crystals contain 500mg of aspirin in each sachet and can be used to relieve pain and inflammation. The granules dissolve on the tongue and can then be swallowed without water.
Aspirin in low doses, eg 75-100mg, does not have this effect and is used instead as an anti-clotting or blood-thinning agent. Low doses of aspirin prevent the production of thromboxane by blood cells called platelets. Thromboxane is one of the chemicals that causes platelets to clump together and start off the clotting process. Stopping its production therefore reduces the likelihood of clots forming in the blood. Clots in the blood can cause a heart attack or stroke, and low dose aspirin is therefore used to prevent this in people who are at risk. See the factsheets linked below for more information about this use of aspirin.
Aspirin is also used in the emergency situation of a heart attack. Anyone who has the symptoms of a heart attack (chest pain, possibly radiating towards the arm or neck, shortness of breath) should take one 300mg aspirin tablet as soon as possible, as this has been shown to increase the chances of surviving a heart attack. This is because the aspirin prevents the blood clot that is blocking the supply of blood to the heart from growing any bigger. A sachet of Alka rapid crystals can also be used for this purpose.
What is it used for?
Warning!
Use with caution in
Not to be used in
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
Pregnancy and Breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
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