CAPP News

Vioxx (refecoxib) withdrawn on safety grounds - 11/02/2005

In October 2004 the pharmaceutical company Merck announced the immediate withdrawal of Vioxx due to an increased rate of cardiovascular 'events' (heart attacks and strokes) in people taking the drug for more than 18 months. This data emerged from the VICTOR trial, a test to see whether this selective COX2 inhibitor might prevent the formation of colonic polyps.

Vioxx is the trade name for rofecoxib, one of a family of drugs (all with the name end "coxib")  developed because they block the enzyme COX2 but do not inhibit COX1. The full name of these two enzymes is cyclooxygenases. They are part of the body's reaction to inflammation. Aspirin blocks them both. Inhibiting COX1 leads to gastric irritation. COX2 is very active in colonic tumours and in inflamed joints.

The drugs were first developed as a "safe aspirin" which could relieve the pain of arthritis without the side effect of stomach ulcers. About  5 years ago a comparison of Vioxx and another aspirin-loke drug called Naprosyn found more heart attcks in the Vioxx group but analysis of all the available data suggested the difference mught be because Naprosyn, like aspirin, is not selective. It was suggested that Naprosyn might protect against heart attacks. This now appears to have been an incorrect assumption.

It does not change the established fact that aspirin protects against heart attacks. Small amounts of aspirin stop the platelets from working. These tiny blood cells are involved in the blood clots which are part of the process leading to a heart attack.

The withdrawal of Vioxx has called into question the use and development of other "coxibs" but it does not affect the CAPP2 Trial. If anything, this discovery reinforces the decision to use aspirin in our trial. Not only do we have the best evidence for it being effective in colon cancer prevention, it is also cheap and its side effects are well understood.