Metformin Hydrochloride Oral Solution Prescribing Information
There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. These cases had a subtle onset and were accompanied by nonspecific symptoms such as malaise, myalgias, abdominal pain, respiratory distress, or increased somnolence; however, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. Metformin-associated lactic acidosis was characterized by elevated blood lactate concentrations (> 5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio; metformin plasma levels were generally > 5 mcg/mL. Metformin decreases liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in patients at risk.
If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, along with immediate discontinuation of metformin hydrochloride oral solution. In metformin hydrochloride oral solution-treated patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin (metformin hydrochloride is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions). Hemodialysis has often resulted in reversal of symptoms and recovery.
Educate patients and their families about the symptoms of lactic acidosis and, if these symptoms occur, instruct them to discontinue metformin hydrochloride oral solution and report these symptoms to their healthcare provider.
For each of the known and possible risk factors for metformin-associated lactic acidosis, recommendations to reduce the risk of and manage metformin-associated lactic acidosis are provided below:
- Renal impairment—The postmarketing metformin-associated lactic acidosis cases primarily occurred in patients with significant renal impairment.
The risk of metformin accumulation and metformin-associated lactic acidosis increases with the severity of renal impairment because metformin is substantially excreted by the kidney. Clinical recommendations based upon the patient’s renal function include [see
- Before initiating metformin hydrochloride oral solution, obtain an estimated glomerular filtration rate (eGFR).
- Metformin hydrochloride oral solution is contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2[seeContraindications].
- Initiation of metformin hydrochloride oral solution is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2.
- Obtain an eGFR at least annually in all patients taking metformin hydrochloride oral solution. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently.
- In patients taking metformin hydrochloride oral solution whose eGFR falls below 45 mL/min/1.73 m2, assess the benefit and risk of continuing therapy.
- Drug interactions— The concomitant use of metformin hydrochloride oral solution with specific drugs may increase the risk of metformin-associated lactic acidosis: those that impair renal function, result in significant hemodynamic change, interfere with acid-base balance, or increase metformin accumulation. Consider more frequent monitoring of patients[see Drug Interactions ].
- Age 65 or greater— The risk of metformin-associated lactic acidosis increases with the patient’s age because elderly patients have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients. Assess renal function more frequently in elderly patients.
- Radiologic studies with contrast —Administration of intravascular iodinated contrast agents in metformin-treated patients has led to an acute decrease in renal function and the occurrence of lactic acidosis. Stop metformin hydrochloride oral solution at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of hepatic impairment, alcoholism or heart failure; or in patients who will be administered intra- arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure, and restart metformin hydrochloride oral solution if renal function is stable.
- 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 oral solution should be temporarily discontinued while patients have restricted food and fluid intake.
- Hypoxic states —Several of the postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure (particularly when accompanied by hypoperfusion and hypoxemia). Cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, discontinue metformin hydrochloride oral solution.
- Excessive alcohol intake —Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving metformin hydrochloride oral solution.
- Hepatic impairment —Patients with hepatic impairment have developed cases of metformin- associated lactic acidosis. This may be due to impaired lactate clearance resulting in higher lactate blood levels. Therefore, avoid use of metformin hydrochloride oral solution in patients with clinical or laboratory evidence of hepatic disease.
- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
Metformin hydrochloride oral solution is contraindicated in patients with:
- Severe renal impairment (eGFR below 30 mL/min/1.73 m2) [seeWarnings and Precautions].
- Hypersensitivity to metformin.
- Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
- Severe renal impairment (eGFR below 30 mL/min/1.73 m2)
- Hypersensitivity to metformin
- Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. These cases had a subtle onset and were accompanied by nonspecific symptoms such as malaise, myalgias, abdominal pain, respiratory distress, or increased somnolence; however, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. Metformin-associated lactic acidosis was characterized by elevated blood lactate concentrations (> 5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio; metformin plasma levels were generally > 5 mcg/mL. Metformin decreases liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in patients at risk.
If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, along with immediate discontinuation of metformin hydrochloride oral solution. In metformin hydrochloride oral solution-treated patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin (metformin hydrochloride is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions). Hemodialysis has often resulted in reversal of symptoms and recovery.
Educate patients and their families about the symptoms of lactic acidosis and, if these symptoms occur, instruct them to discontinue metformin hydrochloride oral solution and report these symptoms to their healthcare provider.
For each of the known and possible risk factors for metformin-associated lactic acidosis, recommendations to reduce the risk of and manage metformin-associated lactic acidosis are provided below:
- Renal impairment—The postmarketing metformin-associated lactic acidosis cases primarily occurred in patients with significant renal impairment.
The risk of metformin accumulation and metformin-associated lactic acidosis increases with the severity of renal impairment because metformin is substantially excreted by the kidney. Clinical recommendations based upon the patient’s renal function include [see
- Before initiating metformin hydrochloride oral solution, obtain an estimated glomerular filtration rate (eGFR).
- Metformin hydrochloride oral solution is contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2[seeContraindications].
- Initiation of metformin hydrochloride oral solution is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2.
- Obtain an eGFR at least annually in all patients taking metformin hydrochloride oral solution. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently.
- In patients taking metformin hydrochloride oral solution whose eGFR falls below 45 mL/min/1.73 m2, assess the benefit and risk of continuing therapy.
- Drug interactions— The concomitant use of metformin hydrochloride oral solution with specific drugs may increase the risk of metformin-associated lactic acidosis: those that impair renal function, result in significant hemodynamic change, interfere with acid-base balance, or increase metformin accumulation. Consider more frequent monitoring of patients[see Drug Interactions ].
- Age 65 or greater— The risk of metformin-associated lactic acidosis increases with the patient’s age because elderly patients have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients. Assess renal function more frequently in elderly patients.
- Radiologic studies with contrast —Administration of intravascular iodinated contrast agents in metformin-treated patients has led to an acute decrease in renal function and the occurrence of lactic acidosis. Stop metformin hydrochloride oral solution at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of hepatic impairment, alcoholism or heart failure; or in patients who will be administered intra- arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure, and restart metformin hydrochloride oral solution if renal function is stable.
- 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 oral solution should be temporarily discontinued while patients have restricted food and fluid intake.
- Hypoxic states —Several of the postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure (particularly when accompanied by hypoperfusion and hypoxemia). Cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, discontinue metformin hydrochloride oral solution.
- Excessive alcohol intake —Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving metformin hydrochloride oral solution.
- Hepatic impairment —Patients with hepatic impairment have developed cases of metformin- associated lactic acidosis. This may be due to impaired lactate clearance resulting in higher lactate blood levels. Therefore, avoid use of metformin hydrochloride oral solution in patients with clinical or laboratory evidence of hepatic disease.
There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. These cases had a subtle onset and were accompanied by nonspecific symptoms such as malaise, myalgias, abdominal pain, respiratory distress, or increased somnolence; however, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. Metformin-associated lactic acidosis was characterized by elevated blood lactate concentrations (> 5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio; metformin plasma levels were generally > 5 mcg/mL. Metformin decreases liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in patients at risk.
If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, along with immediate discontinuation of metformin hydrochloride oral solution. In metformin hydrochloride oral solution-treated patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin (metformin hydrochloride is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions). Hemodialysis has often resulted in reversal of symptoms and recovery.
Educate patients and their families about the symptoms of lactic acidosis and, if these symptoms occur, instruct them to discontinue metformin hydrochloride oral solution and report these symptoms to their healthcare provider.
For each of the known and possible risk factors for metformin-associated lactic acidosis, recommendations to reduce the risk of and manage metformin-associated lactic acidosis are provided below:
- Renal impairment—The postmarketing metformin-associated lactic acidosis cases primarily occurred in patients with significant renal impairment.
The risk of metformin accumulation and metformin-associated lactic acidosis increases with the severity of renal impairment because metformin is substantially excreted by the kidney. Clinical recommendations based upon the patient’s renal function include [see
- Before initiating metformin hydrochloride oral solution, obtain an estimated glomerular filtration rate (eGFR).
- Metformin hydrochloride oral solution is contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2[seeContraindications].
- Initiation of metformin hydrochloride oral solution is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2.
- Obtain an eGFR at least annually in all patients taking metformin hydrochloride oral solution. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently.
- In patients taking metformin hydrochloride oral solution whose eGFR falls below 45 mL/min/1.73 m2, assess the benefit and risk of continuing therapy.
- Drug interactions— The concomitant use of metformin hydrochloride oral solution with specific drugs may increase the risk of metformin-associated lactic acidosis: those that impair renal function, result in significant hemodynamic change, interfere with acid-base balance, or increase metformin accumulation. Consider more frequent monitoring of patients[see Drug Interactions ].
- Age 65 or greater— The risk of metformin-associated lactic acidosis increases with the patient’s age because elderly patients have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients. Assess renal function more frequently in elderly patients.
- Radiologic studies with contrast —Administration of intravascular iodinated contrast agents in metformin-treated patients has led to an acute decrease in renal function and the occurrence of lactic acidosis. Stop metformin hydrochloride oral solution at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of hepatic impairment, alcoholism or heart failure; or in patients who will be administered intra- arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure, and restart metformin hydrochloride oral solution if renal function is stable.
- 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 oral solution should be temporarily discontinued while patients have restricted food and fluid intake.
- Hypoxic states —Several of the postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure (particularly when accompanied by hypoperfusion and hypoxemia). Cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, discontinue metformin hydrochloride oral solution.
- Excessive alcohol intake —Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving metformin hydrochloride oral solution.
- Hepatic impairment —Patients with hepatic impairment have developed cases of metformin- associated lactic acidosis. This may be due to impaired lactate clearance resulting in higher lactate blood levels. Therefore, avoid use of metformin hydrochloride oral solution in patients with clinical or laboratory evidence of hepatic disease.
Metformin hydrochloride oral solution is indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus.
- Starting dose: 500 mg (5 mL) orally twice a day or 850 mg (8.5 mL) once a day, with meals ()
2.1 Adult Dosage- Measure the metformin hydrochloride oral solution dose in the metformin hydrochloride oral solution specific dosing cup.
- The recommended starting dose of metformin hydrochloride oral solution is 500 mg (5 mL) orally twice a day or 850 mg (8.5 mL) once a day, given with meals.
- Increase the dose in increments of 500 mg (5 mL) weekly or 850 mg (8.5 mL) every 2 weeks on the basis of glycemic control and tolerability, up to a maximum dose of 2,550 mg (25.5 mL) per day, given in divided doses.
- Doses above 2,000 mg (20 mL) may be better tolerated given in divided doses 3 times a day with meals.
- Increase the dose in increments of 500 mg (5 mL) weekly or 850 mg (8.5 mL) every 2 weeks, up to a maximum dose of 2,550 mg (25.5 mL) per day, given in divided doses ()
2.1 Adult Dosage- Measure the metformin hydrochloride oral solution dose in the metformin hydrochloride oral solution specific dosing cup.
- The recommended starting dose of metformin hydrochloride oral solution is 500 mg (5 mL) orally twice a day or 850 mg (8.5 mL) once a day, given with meals.
- Increase the dose in increments of 500 mg (5 mL) weekly or 850 mg (8.5 mL) every 2 weeks on the basis of glycemic control and tolerability, up to a maximum dose of 2,550 mg (25.5 mL) per day, given in divided doses.
- Doses above 2,000 mg (20 mL) may be better tolerated given in divided doses 3 times a day with meals.
- Doses above 2,000 mg (20 mL) may be better tolerated given in divided doses 3 times a day with meals ()
2.1 Adult Dosage- Measure the metformin hydrochloride oral solution dose in the metformin hydrochloride oral solution specific dosing cup.
- The recommended starting dose of metformin hydrochloride oral solution is 500 mg (5 mL) orally twice a day or 850 mg (8.5 mL) once a day, given with meals.
- Increase the dose in increments of 500 mg (5 mL) weekly or 850 mg (8.5 mL) every 2 weeks on the basis of glycemic control and tolerability, up to a maximum dose of 2,550 mg (25.5 mL) per day, given in divided doses.
- Doses above 2,000 mg (20 mL) may be better tolerated given in divided doses 3 times a day with meals.
- Starting dose: 500 mg (5 mL) orally twice a day, with meals ()
2.2 Pediatric Dosage- Measure the metformin hydrochloride oral solution dose in the metformin hydrochloride oral solution specific dosing cup.
- The recommended starting dose of metformin hydrochloride oral solution for pediatric patients 10 years of age and older is 500 mg (5 mL) orally twice a day, given with meals.
- Increase dosage in increments of 500 mg (5 mL) weekly on the basis of glycemic control and tolerability, up to a maximum of 2,000 mg (20 mL) per day, given in divided doses twice daily.
- Increase dosage in increments of 500 mg (5 mL) weekly up to a maximum of 2,000 mg (20 mL) per day, given in divided doses twice daily ()
2.2 Pediatric Dosage- Measure the metformin hydrochloride oral solution dose in the metformin hydrochloride oral solution specific dosing cup.
- The recommended starting dose of metformin hydrochloride oral solution for pediatric patients 10 years of age and older is 500 mg (5 mL) orally twice a day, given with meals.
- Increase dosage in increments of 500 mg (5 mL) weekly on the basis of glycemic control and tolerability, up to a maximum of 2,000 mg (20 mL) per day, given in divided doses twice daily.
- Prior to initiation, assess renal function with estimated glomerular filtration rate (eGFR) ()
2.3 Recommendations for Use in Renal Impairment- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
- Do not use in patients with eGFR below 30 mL/minute/1.73 m
2()2.3 Recommendations for Use in Renal Impairment- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
- Initiation is not recommended in patients with eGFR between 30 to 45 mL/minute/1.73 m
2()2.3 Recommendations for Use in Renal Impairment- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
- Assess risk/benefit of continuing metformin hydrochloride oral solution if eGFR falls below 45 mL/minute/1.73 m
2()2.3 Recommendations for Use in Renal Impairment- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
- Discontinue if eGFR falls below 30 mL/minute/1.73 m
2()2.3 Recommendations for Use in Renal Impairment- Assess renal function prior to initiation of metformin hydrochloride oral solution and periodically thereafter.
- Metformin hydrochloride oral solution is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2.
- Initiation of metformin hydrochloride oral solution in patients with an eGFR between 30 to 45 mL/minute/1.73 m2is not recommended.
- In patients taking metformin hydrochloride oral solution whose eGFR later falls below 45 mL/min/1.73 m2, assess the benefit risk of continuing therapy.
- Discontinue metformin hydrochloride oral solution if the patient’s eGFR later falls below 30 mL/minute/1.73 m2[seeWarnings and Precautions].
- Metformin hydrochloride oral solution may need to be discontinued at time of, or prior to, iodinated contrast imaging procedures ()
2.4 Discontinuation for Iodinated Contrast Imaging ProceduresDiscontinue metformin hydrochloride oral solution at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure; restart metformin hydrochloride oral solution if renal function is stable.
Oral solution: 500 mg/5 mL in 5 mL, 8.5 mL, and 10 mL fills in strawberry flavor
- Females and Males of Reproductive Potential: Advise premenopausal females of the potential for an unintended pregnancy. ()
8.3 Females and Males of Reproductive PotentialDiscuss the potential for unintended pregnancy with premenopausal women as therapy with metformin hydrochloride oral solution may result in ovulation in some anovulatory women.
- Geriatric Use: Assess renal function more frequently. ()
8.5 Geriatric UseControlled clinical studies of metformin HCl tablets did not include sufficient numbers of elderly patients to determine whether they respond differently from younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy and the higher risk of lactic acidosis. Assess renal function more frequently in elderly patients [see
Warnings and Precautions]. - Hepatic Impairment: Avoid use in patients with hepatic impairment. ()
8.7 Hepatic ImpairmentUse of metformin in patients with hepatic impairment has been associated with some cases of lactic acidosis. Metformin hydrochloride oral solution is not recommended in patients with hepatic impairment. [see
Warnings and Precautions].
Metformin hydrochloride oral solution is contraindicated in patients with:
- Severe renal impairment (eGFR below 30 mL/min/1.73 m
2) [seeWarnings and Precautions (].)5.1 Lactic AcidosisThere have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. These cases had a subtle onset and were accompanied by nonspecific symptoms such as malaise, myalgias, abdominal pain, respiratory distress, or increased somnolence; however, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. Metformin-associated lactic acidosis was characterized by elevated blood lactate concentrations (> 5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate: pyruvate ratio; metformin plasma levels were generally > 5 mcg/mL. Metformin decreases liver uptake of lactate increasing lactate blood levels which may increase the risk of lactic acidosis, especially in patients at risk.
If metformin-associated lactic acidosis is suspected, general supportive measures should be instituted promptly in a hospital setting, along with immediate discontinuation of metformin hydrochloride oral solution. In metformin hydrochloride oral solution-treated patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin (metformin hydrochloride is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions). Hemodialysis has often resulted in reversal of symptoms and recovery.
Educate patients and their families about the symptoms of lactic acidosis and, if these symptoms occur, instruct them to discontinue metformin hydrochloride oral solution and report these symptoms to their healthcare provider.
For each of the known and possible risk factors for metformin-associated lactic acidosis, recommendations to reduce the risk of and manage metformin-associated lactic acidosis are provided below:
- Renal impairment—The postmarketing metformin-associated lactic acidosis cases primarily occurred in patients with significant renal impairment.
The risk of metformin accumulation and metformin-associated lactic acidosis increases with the severity of renal impairment because metformin is substantially excreted by the kidney. Clinical recommendations based upon the patient’s renal function include [see
Dosage and Administration , Clinical Pharmacology]:- Before initiating metformin hydrochloride oral solution, obtain an estimated glomerular filtration rate (eGFR).
- Metformin hydrochloride oral solution is contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2[seeContraindications].
- Initiation of metformin hydrochloride oral solution is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2.
- Obtain an eGFR at least annually in all patients taking metformin hydrochloride oral solution. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently.
- In patients taking metformin hydrochloride oral solution whose eGFR falls below 45 mL/min/1.73 m2, assess the benefit and risk of continuing therapy.
- Drug interactions— The concomitant use of metformin hydrochloride oral solution with specific drugs may increase the risk of metformin-associated lactic acidosis: those that impair renal function, result in significant hemodynamic change, interfere with acid-base balance, or increase metformin accumulation. Consider more frequent monitoring of patients[see Drug Interactions ].
- Age 65 or greater— The risk of metformin-associated lactic acidosis increases with the patient’s age because elderly patients have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients. Assess renal function more frequently in elderly patients.
- Radiologic studies with contrast —Administration of intravascular iodinated contrast agents in metformin-treated patients has led to an acute decrease in renal function and the occurrence of lactic acidosis. Stop metformin hydrochloride oral solution at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of hepatic impairment, alcoholism or heart failure; or in patients who will be administered intra- arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure, and restart metformin hydrochloride oral solution if renal function is stable.
- 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 oral solution should be temporarily discontinued while patients have restricted food and fluid intake.
- Hypoxic states —Several of the postmarketing cases of metformin-associated lactic acidosis occurred in the setting of acute congestive heart failure (particularly when accompanied by hypoperfusion and hypoxemia). Cardiovascular collapse (shock), acute myocardial infarction, sepsis, and other conditions associated with hypoxemia have been associated with lactic acidosis and may cause prerenal azotemia. When such an event occurs, discontinue metformin hydrochloride oral solution.
- Excessive alcohol intake —Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving metformin hydrochloride oral solution.
- Hepatic impairment —Patients with hepatic impairment have developed cases of metformin- associated lactic acidosis. This may be due to impaired lactate clearance resulting in higher lactate blood levels. Therefore, avoid use of metformin hydrochloride oral solution in patients with clinical or laboratory evidence of hepatic disease.
- Hypersensitivity to metformin.
- Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.