An Irish researcher who was the first to identify a possible link between the drug Vioxx and the risk of heart complaints has welcomed the move by Merck & Co to withdraw the drug.
"I think it was a very responsible move by Merck to withdraw it," said Prof Garret FitzGerald, who is chairman of the Department of Pharmacology at the University of Pennsylvania in Philadelphia.
Researchers have no way of knowing precisely how many Irish patients taking the anti-arthritis drug might face a greater danger of having a heart attack or stroke. Too little is yet known about what patient groups might be most at risk, according to Prof FitzGerald.
Merck yesterday voluntarily withdrew the drug from markets around the world. It is one of the company's biggest selling drugs, achieving estimated annual sales of about $2.5 billion (€2 billion approx).
The shock sent Merck's share value tumbling on stock markets and caused great concern amongst patients taking this and similar drugs.
Prof FitzGerald's research also suggests that all similar drugs, known as Cox-2 inhibitors and that respond to the body's tissues in the same way, may act the same way in patients.
Pfizer is the other leading manufacturer of these drugs with two products, Celebrex and Bextra. Novartis is seeking approval for its new Cox-2 inhibitor and Merck has a second awaiting approval.
"I think it puts a spotlight on the other companies," Prof FitzGerald said. "Those three drugs have the biggest direct to consumer marketing spend of any drug," he added. "It is a $10 billion (€8 million approx) a year market. That is enormous."
The heart attack scare came to light as a result of a large Vioxx drug trial in the US running for the past three years. In this trial, involving 2,600 patients, the drug was being given as a way to prevent the development of pre-cancerous polyps in the colon. Within 18 months, however, some patients began to show increased signs of heart attack and other cardiovascular complications.
The trial was stopped after results suggested that taking the drug long term could increase the risk of heart attack or stroke by between three and four fold compared to patients taking a dummy pill.
The trial provides solid evidence that Prof FitzGerald's earlier findings linking Cox-2 inhibitors and a cardiovascular effect are correct.
"I think the drug clearly works well for people with arthritis," he stated. It also had the advantage of being able to reduce the pain and inflammation associated with osteo-arthritis and rheumatoid arthritis without damaging the stomach.
Initially this outweighed any theoretical risks of heart attack. "What we have now is unequivocal evidence of risk," he said. "We therefore need to get a handle on how we can identify susceptible patients. The at risk group is probably very small." No existing drug trial is designed to deliver this information however so new trials will be needed, he added.
"While the cause of these results is uncertain at this time, they suggest an increased risk of confirmed cardiovascular events beginning after 18 months of continuous therapy," the president of Merck Research Laboratories, Mr Peter Kim, stated yesterday.
In a statement the Irish Medicines Board (IMB) said the potential for development of "cardiovascular adverse effects" was known for some time. "This was highlighted in the patient information leaflet accompanying these products. However, the need for long-term data on cardiovascular safety was identified and this was one of the objectives of this new trial.
"The IMB and its medical experts will participate in a review of other medicinal products in this class, which is scheduled to take place at European level. The results of this review and any necessary regulatory action will be taken and healthcare professionals informed accordingly."