Deson PR Special Precautions

Lactic acidosis is a rare, but potentially severe consequence of therapy with metformin. Lactic acidosis should be suspected in any patient with diabetes receiving metformin with evidence of acidosis but without evidence of ketoaci­dosis. Discontinue metformin in clinical situations predis­posing to hypoxemia, including conditions such as cardiovascular collapse, respiratory failure, acute myocar­dial infarction, acute congestive heart failure, and septice­mia. Use caution in patients with congestive heart failure requiring pharmacologic management, particularly in patients with unstable or acute CHF; risk of lactic acidosis may be increased secondary to hypoperfusion.
Metformin is substantially excreted by the kidney. The risk of accumulation and lactic acidosis increases with the degree of impairment of renal function. Patients with renal function below the limit of normal for their age should not receive metformin. In elderly patients, renal function should be monitored regularly; should not be initiated in patients ≥80 years of age unless normal renal function is confirmed. Use of concomitant medications that may affect renal function (ie, affect tubular secretion) may also affect met­formin disposition. Metformin should be withheld in patients with dehydration and/or prerenal azotemia. Ther­apy should be suspended for any surgical procedures (resume only after normal intake resumed and normal renal function is verified). Therapy should be temporarily discontinued prior to or at the time of intravascular admin­istration of iodinated contrast media (potential for acute alteration in renal function). Metformin should be withheld for 48 hours after the radiologic study and restarted only after renal function has been confirmed as normal. It may be necessary to discontinue metformin and administer insulin if the patient is exposed to stress (fever, trauma, infection, surgery).
Avoid use in patients with impaired liver function. Patient must be instructed to avoid excessive acute or chronic ethanol use; ethanol may potentiate metformin's effect on lactate metabolism. Administration of oral antidiabetic drugs has been reported to be associated with increased cardiovascular mortality; metformin does not appear to share this risk.