9 Nov. 2006

Health Canada approves first new cox-2 drug since Vioxx pulled from market

TORONTO (CP) - Two years after the one-time wonder drugs known as cox-2 inhibitors took a major hit in the public confidence department, drug giant Novartis is bringing a new member of this class to market in Canada.

The company announced Tuesday that it had received Health Canada approval to sell Prexige (lumiracoxib) as a treatment for new acute and chronic pain due to osteoarthritis of the knee in adults.

Prexige is the first new cox-2 to be introduced in this country since the drug class took what appeared at the time to be a near fatal blow with the withdrawal of Merck Frosst's Vioxx - the most popular cox-2 - and Health Canada's request that Pfizer cease selling its drug, Bextra.

Merck pulled Vioxx from the market worldwide after studies showed people on the drug were at almost double the risk of heart attack and stroke as non-users. Bextra was forced off the Canadian market when it was shown to be linked to an increased rate of a rare but life-threatening skin condition in addition to the heart risks.

An expert on cox-2 inhibitors warned that all of the drugs should be used with caution.

"Patients at risk of heart disease should avoid all selective cox-2 inhibitors, including Prexige, based on current evidence," said Dr. Garrett FitzGerald, a cardiologist and pharmacologist at the University of Pennsylvania.

FitzGerald said in an e-mail that use of cox-2s should be "restricted to patients at low risk of heart disease who develop gastrointestinal intolerance" to conventional pain medication such as naproxen or ibuprofen, even if those drugs are taken with medications called proton pump inhibitors, which protect the stomach by lowering acidity levels.

Dr. Andreas Laupacis, who headed an expert panel convened last year to advise Health Canada on the future of the drug class, had mixed feelings about the news that Canada will join the approximately 55 countries that have approved Prexige.

"There are some people who respond to Drug X and just don't respond to Drug Y. And so you can make the argument that having more drugs is better, because some people are going to respond to this new drug who don't respond to the existing ones," said Laupacis, director of the Li Ka Shing Knowledge Institute at Toronto's St. Michael's Hospital.

"The downside of course is there's now another drug company aggressively marketing their drug. And the total number of patients on these drugs may well increase and in some cases increase more than one would think it should on the basis of need."

That's part of the troubled history of cox-2 inhibitors, which became one of the biggest selling classes of drugs of all time after they hit the market in the late 1990s.

Celebrex, Vioxx and the lesser known Bextra were approved based on studies that seemed to show they were effective at combating chronic pain without raising the risk of gastric bleeds, a common problem for people using traditional painkillers like ibuprofen and naproxen. Those older, generic drugs are known as non-steroidal anti-inflammatory drugs or NSAIDs.

Later studies challenged the claims that the drugs were more gastro-protective than NSAIDs, but by then cox-2s were a staple in the enormous market for pain relief.

And while they were brought to market primarily for relief of pain caused by debilitating conditions like osteoarthritis, savvy marketing by drug makers and pervasive off-label prescribing by doctors meant niche drugs became the pain control of choice for a broad spectrum of health ills.

But the drugs' blockbuster status was shattered with Vioxx's revelation that studies it was conducting to see if the drugs could be used to prevent the polyps that can lead to colon cancer actually showed increased risk of cardiovascular events and deaths.

Since Bextra was ordered off the Canadian market in April 2005 Celebrex has been the only drug in the class sold in Canada. But it doesn't appear the drug has benefited to the extent one might have anticipated from the withdrawal of its rivals.

Prescription drug sales data collected by IMS Health shows that 3.4 million prescriptions for cox-2s (Celebrex) were filled in Canada in the 12 months ending June 2006. In 2003, the combined total sales for Celebrex, Bextra and Vioxx were 7.7 million prescriptions.

Still, debate has raged over whether cox-2s should be withdrawn entirely or whether Vioxx and Bextra should be allowed to return to the market.

Drug regulators in Canada and the U.S. held public hearings and in both cases recommended Celebrex should be allowed to remain on the market and Merck should be allowed to resume sales of Vioxx. Merck, which is enmeshed in a number of Vioxx-related lawsuits, has not signalled whether it will attempt to revive the drug.

At the hearings, people suffering from chronic pain pleaded for a return of the discontinued cox-2s, arguing other drugs do not control their pain as effectively. Testimony suggested the drugs are not interchangeable, so Vioxx users might not get the same relief from Celebrex, for instance.

In a release issued by Novartis, John Fleming, president of the Arthritis Society, said the availability of a new treatment option was good news for osteoarthritis sufferers.

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