Metformin/saxagliptin Disease Interactions

There have been postmarketing reports of acute pancreatitis in patients taking DPP-4 inhibitors. These drugs should be used with caution in patients with a history of pancreatitis or pancreatic disease, although it is unknown if they are at increased risk. Patients should be observed for signs and symptoms of pancreatitis during treatment. If pancreatitis is suspected, treatment should be discontinued immediately and appropriate management should be initiated.

Metformin is contraindicated in patients with acute or chronic metabolic acidosis (including diabetic ketoacidosis) with or without coma. Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias; the onset is often subtle and accompanied by nonspecific symptoms (e.g., malaise, myalgias, abdominal pain, respiratory distress, increased somnolence). Risk factors include renal dysfunction, age 65 years and older, hypoxic states, excessive alcohol intake, and liver dysfunction. Lactic acidosis has been associated with metformin accumulation in plasma at levels generally exceeding 5 mcg/mL. The risk of metformin-associated lactic acidosis increases with the patient's age because patients 65 years and older have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients; renal function should be assessed more frequently in older adult patients. Several postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure, especially when accompanied by hypoperfusion and hypoxemia; cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia (e.g., severe anemia, asphyxia) have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, metformin should be discontinued. Dehydration (e.g., severe diarrhea or vomiting) may increase the risk for volume depletion, hypotension, and renal impairment; such patients may be at increased risk for lactic acidosis. Alcohol potentiates the effect of metformin on lactate metabolism; patients should be advised against excessive alcohol intake while receiving metformin. All patients treated with metformin should have renal function monitored regularly (at least annually or more frequently if necessary). If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, as well as immediate discontinuation of metformin. If lactic acidosis is diagnosed or strongly suspected, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin. Patients and their families should be educated about the symptoms of lactic acidosis and, if these symptoms occur, they should be instructed to discontinue metformin and report these symptoms to their health care provider.

Metformin is not recommended in patients with clinical or laboratory evidence of liver disease. Patients with liver dysfunction have developed cases of metformin-associated lactic acidosis. Metformin decreases liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in at-risk patients.

The use of metformin is contraindicated in patients with severe renal dysfunction (estimated GFR [eGFR] less than 30 mL/min/1.73 m2). Metformin is substantially excreted by the kidney; the risk of metformin accumulation and lactic acidosis increases with the degree of renal dysfunction. Before starting metformin, an eGFR should be obtained. Initiation of metformin is not recommended in patients with eGFR between 30 and 45 mL/min/1.73 m2. An eGFR should be obtained at least annually in all patients; in those at risk of developing renal dysfunction (e.g., older adult patients), renal function should be assessed more frequently. In patients whose eGFR falls below 45 mL/min/1.73 m2, the benefit/risk of continuing therapy should be assessed. Postmarketing cases of metformin-associated lactic acidosis primarily occurred with significant renal dysfunction; metformin plasma levels generally exceeded 5 mcg/mL.

It is recommended to assess renal function prior to initiating treatment with DPP-4 inhibitors. Patients with moderate to severe renal insufficiency and end stage renal dysfunction will require a dose adjustment. Linagliptin will not require a dose adjustment per manufacturer's information. Additionally, there have been postmarketing reports of worsening renal function in some patients with renal insufficiency taking sitagliptin at inappropriate doses. However, sitagliptin has not been found to be nephrotoxic in preclinical studies or clinical trials at appropriate doses.

Hypoglycemia may commonly occur during treatment with insulin and/or oral hypoglycemic agents. Care should be taken in patients who may be particularly susceptible to the development of hypoglycemic episodes during the use of these drugs, including those who are debilitated or malnourished, those with defective counterregulatory mechanisms (e.g., autonomic neuropathy and adrenal or pituitary insufficiency), and those receiving beta-adrenergic blocking agents.

Metformin may interfere with vitamin B12 absorption from the B12-intrinsic factor complex. A decrease to subnormal levels of previously normal serum vitamin B12 levels was reported in about 7% of patients treated with metformin during clinical trials. Such decrease may be associated with anemia but appears to be rapidly reversible with metformin discontinuation or vitamin B12 supplementation. Certain patients (those with inadequate vitamin B12 or calcium intake or absorption) appear to be predisposed to developing subnormal levels of vitamin B12; caution may be warranted when metformin is administered to these patients. It is recommended to measure vitamin B12 every 2 to 3 years and hematologic parameters annually in patients on metformin. Any abnormalities should be managed.