Roger Rowe, via facebook asked:
How does Asprin actually work at relieving pain? How does that differ from Paracetamol, Ibuprophen & Codeine?
Aspirin works by inhibiting the production of certain molecules called prostaglandins. These are responsible for promoting inflammation, swelling and pain in areas of the body that have been damaged. They're produced by an enzyme called cyclo-oxygenase or COX and that's the target that aspirin inhibits and actually blocks it from working by binding to the site where the enzyme has its activity. You mentioned some other over-the-counter drugs like ibuprofen and that's actually the same class of drug as aspirin. It operates in a very similar way. Paracetamol is a bit more tricky and it does seem to inhibit COX, but it also has other actions as well and it may act on the cannabinoid receptors in the brain which are actually the same receptors that respond to cannabis, which itself has some painkilling effects. So paracetamol is a bit different to ibuprofen and aspirin, but they're all classed in a similar category which is different to morphine that we heard about before. Aspirin also has the secondary effect to do with preventing blood clots from forming. It does that when given at a slightly lower dose and also over a longer term. That's why the low dose aspirin is given for people at high risk of heart attacks.