Oral medications in NBM patients undergoing radiographic contrast

• Fasting should not be systematic before a radiological examination with injection of iodinated contrast media(ICM)
• Fasting may be useful in some rare instances to visualise the gallbladder, help visualise the gut wall or its viscinity, facilitate specific actions requiring sedation or specific anaesthesia.

Recommendations:

Non diabetic medications

• Take all non diabetic medications as directed. No other medications should be stopped for patients received radiographic contrast media. Unless specifically instructed by their physician, patients should continue taking their regular prescribed medications for diabetes (Insulin, etc), cardiac, and other medical condition(1)

In diabetic patients

• Metformin is not a risk factor for developing contrast induced nephorpathy (CIN) and the injection of CM is not contraindicated in patients taking it.
• However, serious complications (lactic acidosis) may rarely occur in patients taking metformin who subsequently develop AKI
• Metformin should be discontinued on the day of the proposed CM administration, withheld for the subsequent 48 hours and recommenced after renal function has been re-evaluated and found to have returned to baseline 
• The European Society of Urogenital Radiology adopts a conservative approach and recommends holding metformin at the time of injection in patients with normal SCr and 48 hours prior to injection for elective studies in patients with abnormal renal function
• It is generally unnecessary to stop metformin 48 hours prior to contrast injection but special care should be taken in patients with severe or acute renal dysfunction.
• In patients with eGFR < 45 mL/min: Metformin should be stopped at the time of contrast injection and should not be restarted for at least 48 hours and only then if renal function remains stable (less than 25% increase compared to baseline creatinine).
• Certain authors consider it unnecessary to discontinue metformin or recheck renal function following the use of normal volumes (<100mL) of contrast media in patients with normal baseline renal function 

References:
1. http://radres.ucsd.edu/Policies/Contrast%20Media%20Guidelines%20UPDATED%2018Jun2014.pdf
2. http://www.sfrnet.org/data/upload/files/a7e7222e420ac736c1256b6c0044cb07/contrast%20media%20prescribing%20fasting.pdf
3. http://www.car.ca/uploads/standards%20guidelines/20110617_en_prevention_cin.pdf