Australian diabetics taking the controversial drugs Avandia and Avandamet have been told to have their treatment reviewed after the medications were linked with heart failure and death.
More than 30,000 people are taking the two drugs, which were found to double the risk of cardiac failure and mortality in some people in two major studies released last year.
Pharmaceutical company GlaxoSmithKline (GSK) has announced changes to the drugs' guidelines for use, and has urged all patients to see a doctor as soon as possible to discuss their treatment.
Under the new guidelines, no patients with any degree of cardiac failure should take the drugs, and they must not be taken with insulin.
No new patients should be started on so-called triple therapy, a common course of three drugs in combination to treat diabetes.
Dr Michael Elliott, medical director of GSK Australia, said the Therapeutic Goods Administration (TGA) had assessed the available data and decided this was the best course of action for Australian patients.
"Our primary focus is on informing doctors of the changes so they can review the treatment of patients currently on Avandia or Avandamet, in accordance with the changes to the product information," Dr Elliott said.
"Patients using Avandia or Avandamet should continue taking their medication but make an appointment with their doctor to review their treatment as soon as possible."
Avandia, known generically as rosiglitazone, first came under the spotlight in May when a New England Journal of Medicine study found it could increase the risk of heart failure and death by 43 per cent.
This also implicates Avandamet, which is Avandia combined with another diabetes treatment, metformin.
Another report published in Diabetes Care last July showed that Avandia and a related drug, Actos, doubled the risk of heart failure in some patients. No changes have been announced for Actos.
Professor Don Chisholm, an endocrinologist at the Garvan Institute in Sydney, said the insulin and cardiac risk were already known and supported by diabetes specialists.
But the move to stop new patients starting triple therapy was more controversial and would face criticism, Prof Chisholm said.
"I don't agree with it because we know that Avandia in combination therapy is highly effective and the evidence that there's any adverse outcome of using it in triple therapy is very, very minimal," he said.
"Not being able to use it will put people at a disadvantage."
GSK says the changes are not warranted because no adverse data has been seen since 2007 and two new studies released this year support the drugs' safety.
A TGA spokeswoman said the agency was completing a final safety investigation of the medications.