Metformin (INN; trade names Glucophage, Riomet, Fortamet, Glumetza, Diabex, Diaformin, and others) ( ) is an oral anti-diabetic drug from the biguanide class. It is the first-line drug of choice for the treatment of type 2 diabetes, particularly in overweight and obese people and those with normal kidney function. Metformin is the most popular anti-diabetic drug in the United States and one of the most prescribed drugs in the country overall, with nearly 35 million prescriptions filled in 2006 for generic metformin alone. As of 2007, it is one of only two oral anti-diabetics in the World Health Organization Model List of Essential Medicines (the other being glibenclamide).