The commonly used MIR contrast is a gadolinium based compond which are nephrotoxic products, just like iodinated agents used in CT scan. Nevertheless, with the much smaller volume administered—the standard dose is 0.1 mmol/kg (approximately 15–20 mL)—the risk of contrast-induced nephropathy is so low that MR agents are considered virtually nonnephrotoxic.
Therefore, it is not necessary to discontinue metformin/glucophage prior to or after gadolinium-enhanced MR studies when the amount of gadolinium administered is in the usual dose range of 0.1 to 0.3 mmol per kg of body weight, that is less than 20 cc per exam. Metformin should be discontinued in large-dose cases (iodine based x-ray/CT contrast or double-dose MRI contrast exams which are not in use in US currently), such as angiography or CT scanning, where the risk of renal insult is higher.
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