Taking the diabetes drug Actos may increase one's risk of developing bladder cancer, Health Canada and the drug's maker, Takeda Canada Inc., say.
The statement was the culmination of a safety assessment Health Canada announced last June, two days after the U.S. Food and Drug administration issued a warning similar to the one the Canadian drug regulator just announced.
Health Canada said the drug's labelling will be changed to reflect the potential risk.
Actos is the brand name for pioglitazone, a drug from the glitazone family used for the treatment of Type 2 diabetes. It is a sister drug to Avandia, a once widely used diabetes drug that fell out of favour after studies found it increased users' risk of heart disease.
While it was thought that Actos was safer than Avandia — at least in terms of heart disease — there have been suggestions for awhile that using the drug, especially long-term, might increase one's risk of developing bladder cancer.
Takeda is conducting a 10-year study trying to see if the link is real. Data from the midway point of the study points to the possibility that it is, Health Canada said in its statement.
Dr. Muhammad Mamdani, director of the Applied Health Research Centre of the Li Ka Shing Knowledge Institute at Toronto's St. Michael's Hospital, said the warning likely won't impact that many people, because doctors have been moving their patients off the drug over the past few years.
Diabetes treatment options
In fact, in Ontario Actos is no longer on the list of drugs that doctors can freely prescribe; it has been moved to the "exceptional access" list and can only be prescribed with approval, Mamdani said.
Dr. David Juurlink, head of the division of clinical pharmacology at the University of Toronto, said at this point there is little need to resort to this drug, unless a patient has done extraordinarily well on it in the past.
"I personally would not be comfortable using it as a long-term therapy because bladder cancer is …not something that's reversible. It's not a skin rash that goes away when you stop the drug," said Juurlink, who actively campaigned to get Avandia out of use.
"We've got other options. And when you've got other options why would you take an option that has some well-established side-effects and some side-effects that are less well established but ones that you would for sure rather avoid?"
Juurlink suggested that anyone taking the drug who has concerns about this news should speak to their doctor.
The Health Canada statement noted that in the Takeda trial, people who weren't using the drug developed bladder cancer at a rate of about seven cases in every 10,000 people. But there were 10 cases per 10,000 people among the people using Actos for control of Type 2 diabetes.
The statement says the risk appears to be highest for people who took the drug for the longest duration or at the highest dosages, but it isn't possible to rule out a risk even after short-term use.
The drug regulator suggests that Actos should not be used to treat patients with active bladder cancer, a history of bladder cancer or uninvestigated blood in their urine.
It also suggested doctors should assess a patient's risk for bladder cancer before starting treatment with this drug. Known risk factors include age, smoking, a family history of bladder cancer, exposure to chemicals in the workplace, certain cancer treatments and radiation therapy.