Novel non-steroidal anti-inflammatory drugs: what we have learned from animal studies

The use of non-steroidal anti-inflammatory drugs (NSAIDs) is frequently associated with serious adverse effects related to the inhibition of cyclooxygenase (COX) in tissues where prostanoids exert physiological effects, such as gastric mucosal defence, renal homeostasis and platelet aggregation. The discovery of a second COX isoform (COX-2) specifically induced in pathological tissues led to the development of selective COX-2 inhibitors, believed to have an improved safety profile compared to traditional NSAIDs. Animal studies, however, have revealed a protective role for the COX-2 enzyme in the stomach, kidney, heart, vasculature and reproductive system, and therefore, the safety of COX-2 selective inhibitors needs to be reassessed. On the other hand, new therapeutic indications have emerged as a result of the role played by COX-2 overexpression in cancer or Alzheimer's disease. A second approach aimed at obtaining safer NSAIDs is based on the gastroprotective effects of nitric oxide (NO). Traditional NSAIDs chemically linked to NO-releasing moieties retain the therapeutic efficacy, but not the adverse effects, of the parent NSAIDs. Moreover, additional therapeutic applications in cardiovascular diseases, Alzheimer's disease and cancer have been suggested. Animal data, however, need to be confirmed in large clinical trials. Finally, the increase in endogenous NO via a selective increase in inducible NO synthase in the gastric mucosa is the mechanism underlying the good gastric tolerability and the gastroprotective effects of the non-selective NSAID amtolmetin guacyl, documented to date in the rat.