How to manage metformin and gliclazide (sulfonylurea) prior to a colonoscopy?

Management of Metformin and Gliclazide Prior to Colonoscopy

For patients undergoing colonoscopy, metformin should be stopped the night before the procedure, while gliclazide (sulfonylurea) should be withheld on the morning of the procedure with glucose monitoring and infusion if fasting. 1

Metformin Management

Pre-Procedure Recommendations:

• Stop metformin the night before colonoscopy to reduce risk of lactic acidosis 1
• Do not restart metformin until 48 hours after the procedure and after confirming adequate renal function 1, 2
• Assess for risk factors that increase lactic acidosis risk before the procedure:
  • Renal impairment (creatinine clearance <60 mL/min) 1, 3
  • Administration of iodinated contrast agents (if used during procedure) 1, 2
  • Conditions that may alter renal function (dehydration, fasting) 1
  • Severe heart failure (left ventricular ejection fraction <30%) 1

Risk Assessment:

• Check baseline renal function before colonoscopy 3, 2
• Patients with eGFR <45 mL/min/1.73m² are at higher risk of complications 3, 2
• Dehydration from bowel preparation may further compromise renal function 4

Gliclazide (Sulfonylurea) Management

Pre-Procedure Recommendations:

• Withhold gliclazide on the morning of the colonoscopy 1
• For patients remaining NPO (nothing by mouth), consider glucose infusion to prevent hypoglycemia 1
• Monitor blood glucose levels before and during the procedure 2

Risk Considerations:

• Sulfonylureas like gliclazide can cause hypoglycemia during fasting periods 1
• If the patient is scheduled for morning colonoscopy, the risk of hypoglycemia is higher if gliclazide is taken 1
• For emergency procedures where the patient must remain NPO, glucose infusion is recommended if the patient has taken sulfonylureas 1

Special Considerations

Contrast Media (if used):

• If iodinated contrast media is used during colonoscopy, metformin should not be restarted for at least 48 hours 2, 5
• Check renal function before restarting metformin after contrast administration 2, 5
• The risk of contrast-induced nephropathy increases the risk of metformin-associated lactic acidosis 5, 6

Hydration Status:

• Bowel preparation for colonoscopy can cause dehydration 4
• Consider withholding other medications that may worsen dehydration (ACE inhibitors, ARBs, diuretics, NSAIDs) 4
• Adequate hydration should be maintained before and after the procedure 4

Post-Procedure Management

Metformin Restart Criteria:

• Confirm normal renal function before restarting metformin (48 hours post-procedure) 1, 2
• If renal function is impaired, delay restarting metformin until function normalizes 3, 2
• Monitor for symptoms of lactic acidosis (unexplained hyperventilation, myalgias, malaise, unusual somnolence) 2

Gliclazide Restart:

• Resume gliclazide with the first meal after the procedure 1
• Monitor blood glucose levels after restarting medication 2

Common Pitfalls to Avoid

• Failing to stop metformin the night before colonoscopy 1, 7
• Restarting metformin too soon after the procedure without checking renal function 2, 4
• Not providing glucose infusion for patients on sulfonylureas who remain NPO 1
• Overlooking the combined effects of bowel preparation and medication on hydration status 4
• Neglecting to monitor renal function after procedures using contrast media 2, 5