Valdecoxib (Bextra)
Valdecoxib was the third COX-2 selective drug approved by the Food and Drug Administration (FDA) in November 2001. The drug was originally developed by G.D. Searle & Co. and marketed under the brand name Bextra. Pfizer subsequently acquired Searle and has been marketing Bextra worldwide.
A COX-2 inhibitor, similar to Celebrex and Vioxx, Bextra is designed to reduce pain and swelling without causing stomach ulcers, intestinal bleeding and other gastrointestinal side effects normally associated with long-term use of traditional pain relievers such as naproxen (Aleve) and aspirin. The typical dosages for Bextra are 10 to 20 mg.
Bextra is similar to Celebrex in terms of the COX-1/COX-2 enzyme selectivity ratio, which is 60.* This is a more potent selectivity ratio than that of Celebrex at 30, but much less selective than Vioxx at 272. The ratio determines how selective the drug is in blocking the COX-1 versus the COX-2 enzymes. Worldwide sales of Bextra are expected to be $ 1.3 billion in 2004.
Bextra, as well as the other COX-2 drugs, was designed to inhibit the COX-2 enzymes – not the COX-1 enzymes. Since COX-1 enzymes are responsible for the integrity of the stomach and intestinal lining, it was thought that selective inhibition of COX-2 would provide a pain-killing drug that did not have the gastrointestinal side effects associated with traditional pain relievers, such as aspirin, which inhibit COX-1 and COX-2 enzymes equally.
However, studies have indicated that if one type of COX enzymes is reduced too much in the body, the other type could create a very dangerous imbalance. This imbalance presumably is what has lead to heart attacks, strokes, blood clots, and other cardiovascular side effects currently linked to Vioxx usage.
Bextra has also been found to increase the risk of heart attack but more research is needed. Pfizer, the manufacturer of Celebrex and Bextra, has not pulled the drugs from the market, but stopped direct marketing to consumers.
*The drug inhibits COX-2 enzymes 60 times more than COX-1 enzymes.