Q: Are the new arthritis drugs like Vioxx and Celebrex really "super aspirin?"
A: These next-generation non-steroidal anti-inflammatories (NSAIDs) known as COX-2 inhibitors, do not appear to be extra potent but apparently do the same job with fewer side effects. As a result, they may be safer for people, a particular benefit for those requiring these medicines over long periods of time.
Traditional anti-inflammatories like aspirin and ibuprofen are excellent pain relievers and pack an extra punch by reducing inflammation. This double effect comes from divergent chemical actions and timing. Analgesia arrives first, while the anti-inflammatory agents can take days to show an effect. As happens with many drugs, each ingredient may tackle a couple of tasks.
One of the assignments of traditional NSAIDs is to suppress the cyclo-oxygenase (COX) enzyme, the chemical that transforms other substances into potential mediators of inflammation. Because the inflammation promotes the pain, suppressing this COX enzyme can suppress pain.
Unfortunately, these drugs check the COX enzyme throughout the body, not only in inflamed joints, but also where it provides protection such as in the gastrointestinal tract, kidneys, and in the blood, where it boosts clotting. While traditional COX blocking drugs quiet pain and inflammation, they also can leave the stomach, kidneys, and blood defenseless against dangerous erosion and bleeding.
For years, doctors have wished that they could block the COX enzymes in the joints and leave all the good COX in the rest of the body so that patients could take these drugs for months and years without all the problems. While the universe of anti-inflammatory drugs has been expanding as a steady stream of new members emerge, they all have belonged to the same family. Though they differ in potency, how long each dose lasts, and possible side effects, all the anti-inflammatories tinker with what was previously thought to be the one and only COX enzyme.
Then in 1991, researchers looking into the mysteries of inflammation discovered two distinct COX enzymes. The first, COX-1 enzyme, maintains a healthy stomach lining, kidney, blood flow, and platelet function. The second enzyme, COX-2, is not as wide spread, appearing to fuel inflammation where there is tissue damage, but leaving healthy tissue alone. Put another way, the COX-2 enzyme fuels pain-causing inflammation without stirring up the usual unpleasant side effects. Blocking the COX-2 enzyme could offer benefits without the risks.
Pharmaceutical researchers soon devised a drug that suppresses only the COX-2 enzyme and these are the new arthritis drugs you are hearing about. The first two versions are Vioxx and Celebrex, with others sure to follow. Although these newer drugs have far fewer of the conventional side effects of anti-inflammatories, one side effect persists.
When used for extended periods, both the conventional NSAIDs and the newer COX-2 drugs can cause serious effects on the kidneys; continued use should include the monitoring of kidney function. Short-term usage usually does not require the monitoring of kidney function unless kidney problems already exist.
The COX-2 drugs have been called "super aspirin" because they appear to deliver a double whammy, knocking out both inflammation and pain without gut-wrenching side effects. They are probably not significantly stronger than regular NSAIDs. Their appeal is not increased potency, but less collateral damage. There is even a chance that these safer agents might have diminished pain-relieving power, but this is a small price to pay for safety over the long haul.
Scott Fishman, M.D., is a leading expert in pain management.