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On Dec. 19, 2005, the Canadian drug regulator, Health Canada, issued a warning about the possibility of visual impairment with the use of the diabetes drugs rosiglitazone (AVANDIA) and the combination of rosiglitazone with another diabetes drug, metformin (AVANDAMET). The U.S. Food and Drug Administration (FDA) followed with a similar warning on Jan. 5, 2006. The number of reports of vision impairment was not disclosed in the warnings from either Health Canada or the FDA.
Rosiglitazone and...
On Dec. 19, 2005, the Canadian drug regulator, Health Canada, issued a warning about the possibility of visual impairment with the use of the diabetes drugs rosiglitazone (AVANDIA) and the combination of rosiglitazone with another diabetes drug, metformin (AVANDAMET). The U.S. Food and Drug Administration (FDA) followed with a similar warning on Jan. 5, 2006. The number of reports of vision impairment was not disclosed in the warnings from either Health Canada or the FDA.
Rosiglitazone and the combination of the drug with metformin, Avandamet, accounted for more than 10.6 million prescriptions dispensed in the U.S. in 2004.
The full text of the Canadian warning and the FDA warning can be found on the Internet.
Rosiglitazone was approved by the FDA in May 1999 to be used in addition to diet and exercise to improve blood sugar control in patients with type-2 diabetes mellitus, or non-insulin-dependent diabetes. Patients who require insulin injections are termed type-1 diabetes. Rosiglitazone belongs to the family of diabetes drugs known as thiazolidinediones, or glitazones. Pioglitazone (ACTOS) is the only other glitazone currently available on the U.S. market. Troglitazone (REZULIN), the original member of this family, was withdrawn from the market in March 2000 because of liver toxicity (see Worst Pills, Best Pills News April 2000). We have previously urged against use of rosiglitazone or pioglitazone, especially in patients with heart failure (see Worst Pills, Best Pills News, September 2003).
The drug-induced vision abnormality that concerns U.S. and Canadian regulators is known as macular edema. The macula of the eye is the central portion of the retina, a small area rich in structures called cones. Cones are specialized nerve endings that detect color and upon which daytime vision depends. Edema refers to fluid retention and swelling. The swelling of the retina that can result from the use of rosiglitazone appears to be due to fluid leaking from blood vessels within the macula.
As macular edema progresses, blurring occurs in the middle or just to the side of the central visual field. Visual loss from macular edema can progress over a period of months and make it impossible to focus clearly.
Macular edema is common in diabetes. The lifetime risk for diabetics to develop macular edema is about 10 percent . The condition is closely associated with the degree of diabetic retinal disease (retinopathy). High blood pressure and fluid retention also increase the pressure within small blood vessels, called capillaries. The increased pressure drives fluid from within the vessels into the retina. A common cause of fluid retention in diabetes is kidney disease.
What You Can Do
If you experience visual deterioration while taking rosiglitazone or the combination of rosiglitazone with metformin, report this potential adverse drug reaction to your physician as soon as possible.
If you have developed visual problems such as macular edema that may be related to your diabetes, you should not take rosiglitazone or rosiglitazone with metformin. If you are currently taking either of these drugs, ask your physician about other treatment options.
