Central analgesic effects of aspirin-like drugs.

Aspirin-like drugs mainly include paracetamol, salicylates and other non-steroidal anti-inflammatory drugs, and metamizole. Their analgesic effect is classically ascribed to a peripheral site of action, within the pain-processing site. There is, however, convincing evidence that a central component contributes to the overall analgesia provided by these agents. Experimental and clinical studies referring to this challenging proposal are reviewed here. The exact site and mode of action of aspirin-like drugs within the central nervous system remains controversial. It is likely that supraspinal mechanisms play an important role. Some experiments lend support to the involvement of monoaminergic control systems. Other data indicate that these drugs act centrally through the inhibition of cyclo-oxygenase activity. The interactions between prostaglandins and various neurotransmitters suggest that both mechanisms may be linked.