News
By Maithili Chitnavis
|
November 12, 2004
After $2.5 billion in sales last year alone, the manufacturers of the popular prescription drug Vioxx have decided to withdraw the drug from the international market, resulting in the largest withdrawal of a prescription drug in history.After approval from the Food and Drug Administration in 1999, Vioxx was introduced as an anti-inflammatory drug for the treatment of acute pain and arthritis.Five-and-a-half years later, over 80 million patients in more than 80 countries have received treatment.
Now studies show that continuous therapy for a period greater than 18 months can increase risks of heart attack and stroke in patients.While some have been highly critical of the manufacturers of Vioxx (Merck & Co., Inc.), the FDA, and other international regulatory bodies for not designing trials specifically anticipating cardiovascular risks associated with Vioxx, other professionals feel that Vioxx is still a relatively safe drug and that there is not enough evidence to prove that it is the sole cause of increased risks in patients.Rofecoxib, the chemical name for Vioxx, falls into a class of drugs known as Cyclooxygenase-2 (COX-2) inhibitors, which includes such drugs as Celebrex (celecoxib).These inhibitors work by specifically targeting the COX-2 enzyme and by blocking the enzyme that produces chemical messengers responsible for the pain and swelling associated with arthritis.As a result, inflammation is reduced.
COX-2 inhibitors, in turn, are part of a larger class of drugs known as non-steroidal anti-inflammatory drugs (NSAIDs).The other NSAIDs, which include aspirin and ibuprofen (Advil, Motrin, etc.), are different from COX-2 inhibitors in that they target both COX-1 and COX-2 enzymes.When the COX-1 enzyme is blocked, the protective lining in the stomach is reduced, leading to upset stomach, internal bleeding, and possibly ulcers.Over the past few years, Merck designed studies investigating the possibilities as to whether or not Vioxx could lead to these gastrointestinal side effects.
The two clinical studies, the APPROVe (Adenomatous Polyp Prevention on Vioxx) trial and the VIGOR (Vioxx Gastrointestinal Outcomes Research) study, showed that Vioxx had a lower rate of the gastrointestinal risks that were typically associated with NSAIDs.One of the major reasons Vioxx was such a popular drug is the fact that, according to the FDA, "Vioxx is the only NSAID demonstrated to have a lower rate of these side effects."However, while the studies revealed promising information, they unexpectedly indicated something else:relatively increased risks of cardiovascular events, such as heart attack or stroke.
The results of the VIGOR study, which were released in March 2000, only showed increased cardiovascular risks when compared to naproxen (Aleve), another NSAID.However, Vioxx did not show these risks compared to placebo or other NSAIDs.
Dr. Steven Snapinn, former senior director of the Department of Biostatistics for Merck Research Laboratories, worked in cardiovascular drug development for 20 years.He is one such professional who believes that it is still not clear whether or not Vioxx causes cardiovascular events.
