Recent research shows that by the time someone is diagnosed with Type-2 diabetes, their insulin producing capacity is already reduced to around 65%, because the body has been trying to compensate for increasing insulin resistance for years. Sulfonylureas hasten this degradation.
The main difference between the two medications is in how quickly they start working and how long they remain effective. The more common glipizide (brand name Glucotrol) peaks in 1-3 hours and generally lasts 12 hours in most people. Glyburide (brand names Micronase and DiaBeta) peaks later, usually in four hours, and stays active in the body for 24 hours. Interestingly, Glyburide has been shown to be an especially helpful medication for diabetic cats, but doesn’t seem to help with dogs who have diabetes. Go figure.