Mechanism of action
Analgesic effect is both due to peripheral and central action. It is effective against somatic pain. Analgesic activity is probably mediated through inhibition of the prostaglandin synthetase enzyme complex. Antipyresis results from its action on hypothalamus which produces vasodilation of peripheral vessels thus enhancing dissipation of excess heat. Aspirin does not decrease temperature which is increased by exercise or heat. It does not lower the normal body temperature. At toxic doses salicylates cause stimulation of CNS followed by depression.