Cyclooxygenase (COX)

Cyclooxygenase (COX):
• found in all tissues of the body
• following injury, COX catalyses the synthesis of prostaglandin E2 (PGE2) and prostaglandin I2 (PGI2)  inflammation
• in stomach, PGE2 & PGI2 help protect gastric mucosa
• in platelets, promotes synthesis of thromboxane A2 (TXA2)  promotes platelet aggregation
• in brain  mediates fever and decreases pain perception
• in kidney  promotes vasodilation to maintain renal blood flow
• two forms COX-1 and COX-2:
• COX-1 – present in all body tissues  functions to protect gastric mucosa, maintain renal blood flow, promotes platelet aggregation (helpful processes)
• COX-2 – found at sites of tissue injury  mediates inflammation and pain perception; and in brain  pain perception (harmful processes)

Inhibition of COX-1  gastric erosion, increased tendency to bleed, renal failure, prevention of cardiac events (reduced platelet aggregation)
Inhibition of COX-2  suppression of inflammation, pain relief, fever reduction

Classification:
First generation:
• inhibit both COX-1 and COX-2
• one of most widely used drug groups
• eg aspirin, ibuprofen

Second generation:
• inhibit only COX-2