Preventing Type 2 Diabetes
Can drugs prevent the onset of type 2 diabetes? One class of drugs shows promise, but it has its drawbacks.
A New Direction? continued...
However, other experts caution that the results of the TRIPOD study and the effectiveness and safety of TZDs need to be confirmed.
"TZDs are an incredibly important addition to our set of tools," says Fran Kaufman, president of the American Diabetes Association and division head of endocrinology at the Children's Hospital Los Angeles. But she cautions that more studies need to be done. "Whether other studies will show a similarly robust effect of TZDs [as the TRIPOD study did] is something we just don't know."
The Risks and The Costs
There are potential dangers to TZDs. This was most evident in 2000, when the Food and Drug Administration asked the manufacturer of Rezulin to withdraw it after reports of severe and sometimes fatal liver poisoning. The two other TZDs that are currently available, Actos and Avandia, have not shown the same risks and other TZDs are currently in various stages of development. However, the FDA still recommends that liver function of people using TZDs be tested regularly.
The problems with Rezulin illustrate the risks of using any newly developed drug. "Like any drug that's only been used for a short time, we just don't know what the long-term risks might be of TZDs," Buchanan says.
As noted, TZDs have also been connected with weight gain. While the extra fat may be subcutaneous, and thus not as dangerous as visceral fat, the long-term effects of the weight increase aren't known; some patients gain so much weight that treatment needs to be stopped. Studies have also shown an increase in the risk of edema -- the build-up of fluid in tissue -- from TZD use.
There have been reports of other potential problems, and one survey of patients using TZDs found that the risk of congestive heart failure actually increased, in contrast to studies demonstrating the cardio-protective characteristics of the drugs.
Finally, the financial costs of TZDs may hamper their usefulness; they are significantly more expensive than other drugs used to treat diabetes. While Kaufman hopes that prices will drop as more TZDs are released, Buchanan is concerned that this may not happen until the patents on particular TZDs expire.