11.02.3 Drugs that Modify the Arachidonic Acid Pathway

Non steroidal anti-inflammatory drugs (NSAIDs) are cyclo-oxygenase inhibitors that prevent the production of the prostanoids from arachidonic acid. These drugs are effective analgesics, anti-inflammatory agents and anti-pyretic agents. Most NSAIDs are non-specific and block both COX-1 and COX-2 (e.g. aspirin, ibuprofen, diclofenac), but COX-2 selective agents (e.g. celecoxib) were developed to target COX-2 at sites of inflammation and thus reduce side effects. However, these drugs may precipitate adverse cardiovascular effects and have limited use. Adverse effects of NSAIDs relate to inhibition of their gastro-protectant properties (eg PGE₂ increases cytoprotective mucus secretion and decreases gastric acid secretion). PGE₂ mimetics (e.g. misoprostol) are used to treat peptic ulcer disease (PUD) and can be given with long-term NSAID use to reduce the incidence of these side effects.

Paracetamol is another Other-The-Counter (OTC) pain killer that is reported to act by blocking COX. However it has no anti-inflammatory effects, and this is suggested to be because it only acts at a form of COX in the central nervous system (CNS). Paracetamol has good analgesic and anti-pyretic effects.