Arachidonic acid metabolism, pain and hyperalgesia: the mode of action of non-steroid mild analgesics.

1 Cyclo-oxygenase products such as prostaglandins of the E series and prostacyclin produce the hyperalgesia associated with inflammation. 2 These substances may cause pain and incapacity in some inflammatory conditions. 3 Prostaglandin E2 sensitizes the chemical receptors of afferent pain endings to other inflammatory mediators such as bradykinin and histamine. 4 Unstable intermediates formed in the generation of prostaglandins may also play a role in the production of pain. 5 Drugs such as indomethacin and aspirin which are potent inhibitors of prostaglandin biosynthesis may exert their analgesic effect through this mechanism.