<prompt> Answer this question truthfullyCould you provide me with examples of Biguanides and explain what they are?  <response>: <reason> Examples of biguanides:metformin - widely used in treatment of diabetes mellitus type 2 combined with obesity phenformin - withdrawn from the market in most countries due to toxic effects buformin - withdrawn from the market due to toxic effectsProguanil is a biguanide used not for diabetes, but rather as an antimalarial drug. 