COX Inhibitors: The Chemistry of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of medications used to alleviate pain, reduce inflammation and lower fever. Common NSAIDs include aspirin, ibuprofen, and naproxen.

Some common NSAID drugs

They function by inhibiting the production of prostaglandins by cyclooxygenase (COX) enzymes. Prostaglandins are substances in the body that promote the inflammatory response.

The conversion of arachidonic acid to prostaglandins by COX enzymes

Two COX isozymes, COX-1 and COX-2. The COX-1 isozyme serves a maintenance function in healthy cells, whilst the COX-2 isozyme is produced in response to injury and is involved in the inflammatory response to tissue damage. Inhibition of COX-2 is responsible for the anti inflammatory effect. However, the NSAIDs shown above also inhibit the constitutive COX-1 isozyme, which regulates platelet aggregation, gastrointestinal protection and kidney function. Unwanted COX-1 inhibition can result in gastric toxicity and therefore COX inhibitors which selectively target COX-2 are sought.

Structure of the COX-1 enzyme

The discovery of the COX-2 isozyme led to the development of many COX-2 selective inhibitors, for example rofecoxib, valdecoxib and celecoxib, which exhibited a safer gastric toxicity profile.

Selective COX-2 inhibitors

However, many of the launched COX-2 drugs produced an increased risk of heart attack and stroke. As a result, rofecoxib was withdrawn worldwide in 2004, and valdecoxib was withdrawn from the US and European markets in 2005. Celecoxib remains available in the United States and Europe, but carries a boxed warning. Thus, the search for COX inhibitors without side effects remains active.