Health Canada and drug giant Pfizer formally announced Monday the company is taking a drug used to treat a rare, but serious, lung disease off the market due to risks of potentially fatal liver damage.
Pfizer Canada also said the company is abandoning all clinical trials of sitaxsentan sodium, better known by the brand name Thelin, and removing the drug from every country where it is sold.
The decision is raising questions about why the drug, used to treat pulmonary hypertension, was approved in Canada in the first place.
Parent company Pfizer Inc. announced more than a week ago its intentions to pull the drug off the market in Canada, Australia and Europe, as well as halt clinical trials. The decision was prompted by the deaths of three patients involved in clinical trials of the drug.
The company was conducting the trials in a bid to get the U.S. Food and Drug Administration to approve the drug in that country.
The FDA had rejected several applications from Pfizer to have the drug approved for sale in the U.S., amid fears that the side effects associated with Thelin outweighed any potential benefit.
But Health Canada gave approval to Thelin in 2007. Nearly 1,000 prescriptions for the drug were dispensed by Canadian retail pharmacies from January to October of this year, according to IMS Brogan, a company that tracks the pharmaceutical industry.
The Pulmonary Hypertension Association of Canada estimates that between 2,000 and 5,000 Canadians have been diagnosed with the disease. Several thousand more Canadians may have the disease, but are undiagnosed.
Pulmonary hypertension is characterized by constriction or thickening of pulmonary arteries, or the blood vessels that carry blood from the heart to the lungs. This makes it more difficult for the heart to pump blood to the lungs, which can lead to low oxygen levels in the blood, heart failure or other serious problems.
Although liver damage was a known complication of Thelin, Pfizer said it discovered a "new potentially life-threatening idiosyncratic risk" of liver injury among patients that is difficult to predict or guard against.
The decision means patients with pulmonary hypertension who were taking the drug will now have to find alternate treatments and raises the question of how many patients may have been put in harm's way by taking Thelin.
Julie-Catherine Racine, senior manager of corporate communications at Pfizer Canada, said only 107 patients were taking the drug in Canada, and are being transferred to other medications. She said no deaths or adverse events were linked to the drug in Canada.