Toronto — Two drugs used to treat Type 2 diabetes have been found to cause or worsen a serious vision impairment known as macular edema, Health Canada warned Wednesday.
The advisory was released after GlaxoSmithKline Inc., the manufacturer of Avandia and Avandamet, informed Health Canada of reports that some diabetics on the drugs had developed the eye condition or had a pre-existing case worsen.
Symptoms of macular edema include blurred or distorted vision, decreased colour sensitivity and poorer adaptation to the dark. Patients on Avandia and Avandamet also reported fluid retention, swelling of the extremities and weight gain, whether using one of the drugs alone or in combination with other medications.
The company says patients taking the tablets, which contain the ingredient rosiglitazone, should not stop taking the drugs, but should consult their eye specialist. Doctors are being advised to consider whether the medications should be discontinued for individual patients.
“In some cases, the visual impairment was reported to have improved or resolved following discontinuation of Avandia or Avandamet,” GlaxoSmithKline said in a letter to health professionals posted on Health Canada's drug and health products website.
In that letter, the company warns doctors that Avandia and Avandamet “should be used with caution in patients with a pre-existing diagnosis of macular edema or diabetic retinopathy.”
Macular edema is a swelling of the retina due to fluid at the back of the eye and may be more likely to occur in people with diabetic retinopathy (a disease of the retina caused by diabetes), high blood pressure and/or poor control of blood-sugar levels.
Diabetics taking either of the drugs are advised to:
—See your doctor if experiencing any of the following symptoms: blurred or distorted vision, decreased colour sensitivity and/or decreased ability to adapt to darker surroundings.
—If already diagnosed with macular edema or diabetic retinopathy, see your doctor to assess whether Avandia or Avandamet treatment should be continued.
—Do not stop taking your medication without first consulting your doctor, as an increase in blood-sugar levels could cause medical problems.
