Recent studies reveal that thiazolidinediones like pioglitazone (Actos) and rosiglitazone (Avandia) pose both an increased risk of vision problems due to diabetic macular edema and bladder cancer for patients with type 2 diabetes.
 
According to MedicineNet, blurred vision and an inability to focus are symptoms of diabetic macular edema, or retina swelling caused by leaking fluid from blood vessels within a small part of the retina called the macula that is largely responsible for daytime vision and color detection. In a study conducted by Dr. Iskander Idris of Sherwood Forest Hospitals Foundation Trust in Nottingham, England and published in the Archive of Internal Medicine, over 103,000 type 2 diabetes patients with no history of eye problems were assessed for effects caused by treatment with Actos and Avandia). Researchers found that 2.3 percent of those taking the drug longer than a year developed diabetic macular edema, compared to 0.2 of people not taking the drug.
 
Dr. Sonal Singh of Johns Hopkins University School of Medicine co-authored an accompanying journal editorial that suggested the study’s weakness lies in the inability to determine whether the increase in vision problems is due to the thiazolidinediones or the disease itself. Diabetes, WebMD states, is the most common source of blindness in people ages 20 to 74. According to WebMD, high blood sugar levels contribute to diabetes-related eye issues, and thiazolidinediones are only prescribed to patients who could not regulate their blood sugar levels on other medications.
 
Actos has also been linked to an increased risk of bladder cancer, according to a data gathered from 155,727 patients treated with the anti-diabetic drug between 1988 and 2009 in the U.K. Avandia has not produced the same effects. MedicineNet says bladder cancer is a common type of cancer and begins in the lining of the bladder before expanding to the organ’s muscular wall and other organs.
 
An analysis of the data revealed that 470 type 2 diabetic patients taking Actos were diagnosed with bladder cancer during the average 4.6 years of follow-up. Any use of the drug was associated with an increased risk of developing bladder cancer by 83 percent.
 
Though effective in lowering blood sugar levels in individuals with Type 2 diabetes, thiazolidinediones should be carefully considered before being prescribed due to the severity of possible adverse effects.