How does paracetamol work? ( Pharmacology Of Paracetamol )

Paracetamol is generally considered to be a weak inhibitor of the enzyme cyclooxygenase-2 (COX-2). This enzyme is important in the synthesis of prostaglandins (PG), so by inhibiting the action of COX-2, paracetamol causes a decrease in PG production. Prostaglandins are important mediators of inflammation, and their release has many effects including the sensitization of nerve cells to pain, and a direct effect on the hypothalamus in the brain resulting in fever.

Although paracetamol suppresses inflammation in mice and rats and can reduce swelling after surgery in humans, it is not effective in reducing inflammation in all cases, for example it has no anti-inflammatory effect in rheumatoid arthritis in humans.

Some evidence suggests that the analgesic effect of paracetamol is due to a central effect on the production of serotonin. Serotonin is a neurostransmitter which helps alleviate pain, and short term use of paracetamol has been shown to cause an increase in serotonin levels in the central nervous system.Longer term use of paracetamol is associated with a decrease in serotonin levels, and this is believed to be the cause of analgesic-induced headaches.