When should metformin (biguanide oral hypoglycemic) be held before and after cardiac catheterization and stent placement?

From the Guidelines

Metformin should be withheld on the day of surgery or procedure, and its use should be reassessed after the procedure, taking into account the patient's renal function, as recommended by the most recent guidelines 1. When considering the management of metformin in the context of cardiac catheterization and stent placement, it's crucial to prioritize the patient's safety and minimize the risk of complications such as lactic acidosis. The use of contrast media during these procedures can potentially impair kidney function, leading to an increased risk of lactic acidosis if metformin accumulates in the body. Key considerations include:

• Withholding metformin on the day of the procedure, as suggested by the 2021 standards of medical care in diabetes 1.
• Monitoring renal function closely after the procedure, especially in patients who have received contrast media.
• Restarting metformin only when renal function has been confirmed to be stable, to minimize the risk of lactic acidosis.
• Ensuring that patients stay well-hydrated before and after the procedure to help protect kidney function.
• Monitoring blood glucose levels frequently during the metformin pause and implementing alternative glucose-lowering strategies as needed, particularly for insulin-dependent diabetics. It's also important to note that the plasma half-life of metformin is approximately 6.2 hours, but the decision to withhold or restart metformin should be based on the patient's clinical status and renal function rather than the drug's half-life alone, as emphasized in the 2014 ESC/EACTS guidelines on myocardial revascularization 1. Ultimately, the management of metformin in the context of cardiac catheterization and stent placement should be individualized, taking into account the patient's specific clinical circumstances and the potential risks and benefits of continuing or withholding the medication, as recommended by the 2020 ESC guidelines on diabetes, pre-diabetes, and cardiovascular diseases 1.

From the FDA Drug Label

Surgery and other procedures —Withholding of food and fluids during surgical or other procedures may increase the risk for volume depletion, hypotension, and renal impairment. Metformin hydrochloride tablets should be temporarily discontinued while patients have restricted food and fluid intake

The decision to hold metformin before and after cardiac catheterization and stent placement should be based on the patient's individual risk factors, such as renal impairment.

• Temporarily discontinue metformin hydrochloride tablets while patients have restricted food and fluid intake.
• Consider the patient's renal function and risk of lactic acidosis when making this decision.
• There is no specific guidance on the exact timing of when to hold metformin, but it is recommended to temporarily discontinue metformin during periods of restricted food and fluid intake 2.

From the Research

Metformin Hold Duration for Cardiac Catheter and Stent Placement

• The decision to hold metformin before and after cardiac catheterization and stent placement should be based on individual patient factors, rather than a generic policy 3.
• There is no evidence to support stopping metformin 48 hours before and 48 hours after the procedure in all patients 3.
• Some studies suggest that metformin can be continued until the day of surgery and resumed shortly after, without an increased risk of lactic acidosis 4.
• However, other studies recommend discontinuing metformin at least 2 days before surgery to minimize the risk of lactic acidosis 5.
• The risk of lactic acidosis is more closely related to factors such as tissue anoxia, shock, and acute kidney or liver injury, rather than metformin use itself 4.

Key Findings

• A study of 142 diabetic patients undergoing coronary angiography found no significant increase in lactate levels when metformin was continued throughout the periprocedural period 6.
• Another study of 127 patients with type 2 diabetes undergoing coronary artery bypass grafting found no difference in clinical outcomes or complications between patients who continued taking metformin and those who took other antidiabetic agents 4.
• The estimated incidence of metformin-induced lactic acidosis is 2-9 cases per 100,000 patients, and is often associated with underlying conditions such as renal failure or heart failure 7.

Considerations for Metformin Use

• Patients with heart failure or renal impairment may be at increased risk of lactic acidosis, and metformin use should be carefully considered in these patients 3, 7.
• The benefits of metformin use, including improved glycemic control and reduced risk of cardiovascular events, should be weighed against the potential risks of lactic acidosis 3, 4.