The Metformin (glucophage) product information has been updated and now contains the following warning:-
"Intravascular contrast studies with iodinated materials can lead to acute alteration of renal function and have been associated with lactic acidosis in patients receiving Metformin. Therefore, in patients in whom any such studies are planned, Metformin should be discontinued at the time of, or prior to, the procedure and withheld for 48 hours subsequent to the procedure and re-instituted only after renal function has been re-evaluated and found to be normal."
Based on the above statement, the following are the Royal College of Radiologists recommendations for patients with Diabetes Mellitus who are receiving Metformin and who are referred for a radiological investigation using intravascular contrast media.
- The referring clinician should take responsibility for assessing the patients' renal function, either by checking the serum creatinine or accepting a normal level within the past year. The Radiology Department should inform the referring clinician of the timing of the investigation to enable this to occur.
- In patients with normal renal function, although there are as yet no reports of Metformin-induced lactic acidosis in the United Kingdom after intravenous contrast agents, there is a remote theoretical risk of interaction. Metformin should therefore be discontinued at the time of the investigation and withheld for the subsequent 48 hours.
- For those patients with abnormal renal function, Metformin should similarly be discontinued at the time of the investigation and the subsequent 48 hours, and only reinstated when renal function has been re-evaluated and found to be normal.
- As the British Diabetic Association states that Metformin is contra-indicated in the presence of abnormal renal function, it is suggested that such patients who require intravascular contrast examinations should have their drug history reviewed by the appropriate physician to ensure suitability of the drug regime.
Professor Jamie Weir
Vice-President and Dean
Faculty of Clinical Radiology
19th March 1999