Drug Facts
Composition & Profile
Identifiers & Packaging
16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Metformin Hydrochloride Extended-Release Tablets, USP are available containing 500 mg or 1000 mg of metformin hydrochloride, USP. The 500 mg tablets are pink, film-coated, round, unscored tablets imprinted with M over MN2 in black ink on one side of the tablet and blank on the other side. They are available as follows: NDC 0378-6002-91 bottles of 60 tablets The 1000 mg tablets are pink, film-coated, round, unscored tablets imprinted with M over MN1 in black ink on one side of the tablet and blank on the other side. They are available as follows: NDC 0378-6001-91 bottles of 60 tablets 16.2 Storage Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature.] Avoid excessive heat and humidity. Protect from light and moisture. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep tightly closed.; PACKAGE/LABEL PRINCIPAL DISPLAY PANEL – 500 mg NDC 0378-6002-91 Once-a-Day Metformin HCl Extended-Release Tablets, USP 500 mg Rx only 60 Tablets Each film-coated tablet contains: Metformin hydrochloride, USP 500 mg Usual Dosage: See accompanying prescribing information. Extended-release tablets should not be broken, crushed or chewed. Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.] Protect from light and moisture. Avoid excess heat and humidity. Manufactured for: Mylan Pharmaceuticals Inc. Morgantown, WV 26505 U.S.A. Made in India Mylan.com RMX6002D3 Keep this and all medication out of the reach of children. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep container tightly closed. Code No.: MH/DRUGS/25/NKD/89 Metformin Hydrochloride Extended-Release Tablets 500 mg Bottle Label; PACKAGE/LABEL PRINCIPAL DISPLAY PANEL – 1000 mg NDC 0378-6001-91 Once-a-Day Metformin HCl Extended-Release Tablets, USP 1000 mg Rx only 60 Tablets Each film-coated tablet contains: Metformin hydrochloride, USP 1000 mg Usual Dosage: See accompanying prescribing information. Extended-release tablets should not be broken, crushed or chewed. Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.] Protect from light and moisture. Avoid excess heat and humidity. Manufactured for: Mylan Pharmaceuticals Inc. Morgantown, WV 26505 U.S.A. Made in India Mylan.com RMX6001D3 Keep this and all medication out of the reach of children. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep container tightly closed. Code No.: MH/DRUGS/25/NKD/89 Metformin Hydrochloride Extended-Release Tablets 1000 mg Bottle Label
- 16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Metformin Hydrochloride Extended-Release Tablets, USP are available containing 500 mg or 1000 mg of metformin hydrochloride, USP. The 500 mg tablets are pink, film-coated, round, unscored tablets imprinted with M over MN2 in black ink on one side of the tablet and blank on the other side. They are available as follows: NDC 0378-6002-91 bottles of 60 tablets The 1000 mg tablets are pink, film-coated, round, unscored tablets imprinted with M over MN1 in black ink on one side of the tablet and blank on the other side. They are available as follows: NDC 0378-6001-91 bottles of 60 tablets 16.2 Storage Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature.] Avoid excessive heat and humidity. Protect from light and moisture. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep tightly closed.
- PACKAGE/LABEL PRINCIPAL DISPLAY PANEL – 500 mg NDC 0378-6002-91 Once-a-Day Metformin HCl Extended-Release Tablets, USP 500 mg Rx only 60 Tablets Each film-coated tablet contains: Metformin hydrochloride, USP 500 mg Usual Dosage: See accompanying prescribing information. Extended-release tablets should not be broken, crushed or chewed. Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.] Protect from light and moisture. Avoid excess heat and humidity. Manufactured for: Mylan Pharmaceuticals Inc. Morgantown, WV 26505 U.S.A. Made in India Mylan.com RMX6002D3 Keep this and all medication out of the reach of children. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep container tightly closed. Code No.: MH/DRUGS/25/NKD/89 Metformin Hydrochloride Extended-Release Tablets 500 mg Bottle Label
- PACKAGE/LABEL PRINCIPAL DISPLAY PANEL – 1000 mg NDC 0378-6001-91 Once-a-Day Metformin HCl Extended-Release Tablets, USP 1000 mg Rx only 60 Tablets Each film-coated tablet contains: Metformin hydrochloride, USP 1000 mg Usual Dosage: See accompanying prescribing information. Extended-release tablets should not be broken, crushed or chewed. Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.] Protect from light and moisture. Avoid excess heat and humidity. Manufactured for: Mylan Pharmaceuticals Inc. Morgantown, WV 26505 U.S.A. Made in India Mylan.com RMX6001D3 Keep this and all medication out of the reach of children. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure. Keep container tightly closed. Code No.: MH/DRUGS/25/NKD/89 Metformin Hydrochloride Extended-Release Tablets 1000 mg Bottle Label
Overview
Metformin hydrochloride extended-release tablets, USP contain the biguanidine antihyperglycemic agent, metformin, in the form of monohydrochloride salt. The chemical name of metformin hydrochloride is 1,1-Dimethybiguanide monohydrochloride with a molecular formula of C 4 H 11 N 5 •HCl and a molecular weight of 165.6. Its structural formula is: Metformin hydrochloride, USP is a white crystalline powder that is freely soluble in water and is practically insoluble in acetone, ether, and chloroform. The pKa of metformin is 12.4. The pH of a 1% aqueous solution of metformin hydrochloride is 6.68. Metformin hydrochloride extended-release tablets deliver 500 mg or 1000 mg of metformin hydrochloride. In addition to the active ingredient metformin hydrochloride, each tablet contains the following inactive ingredients: cellulose acetate, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone, red iron oxide, sodium lauryl sulfate, talc, titanium dioxide, triacetin, triethyl citrate and yellow iron oxide. In addition, the black imprinting ink contains ammonium hydroxide, black iron oxide, propylene glycol and shellac glaze. Meets USP Dissolution Test 5. Metformin hydrochloride structural formula
Indications & Usage
Metformin hydrochloride extended-release tablets are indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Metformin hydrochloride extended-release tablets are a biguanide indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. ( 1 )
Dosage & Administration
• Swallow metformin hydrochloride extended-release tablets whole and never crush, cut or chew ( 2.1 ) • Starting dose: 500 mg orally once daily with the evening meal ( 2.1 ) • Increase the dose in increments of 500 mg weekly, up to a maximum of 2000 mg once daily with the evening meal ( 2.1 ) • Patients receiving metformin hydrochloride (HCl) tablets may be switched to metformin hydrochloride extended-release tablets once daily at the same total daily dose, up to 2000 mg once daily ( 2.1 ) Renal Impairment: • Prior to initiation, assess renal function with estimated glomerular filtration rate (eGFR) ( 2.2 ) o Do not use in patients with eGFR below 30 mL/minute/1.73 m 2 ( 2.2 ) o Initiation is not recommended in patients with eGFR between 30 to 45 mL/minute/1.73 m 2 ( 2.2 ) o Assess risk/benefit of continuing if eGFR falls below 45 mL/minute/1.73 m 2 ( 2.2 ) o Discontinue if eGFR falls below 30 mL/minute/1.73 m 2 ( 2.2 ) Discontinuation for Iodinated Contrast Imaging Procedures: • Metformin hydrochloride extended-release tablets may need to be discontinued at time of, or prior to, iodinated contrast imaging procedures ( 2.3 ) 2.1 Adult Dosage and Administration • Swallow metformin hydrochloride extended-release tablets whole and never crush, cut or chew. • The recommended starting dose of metformin hydrochloride extended-release tablets is 500 mg orally once daily with the evening meal. • Increase the dose in increments of 500 mg weekly on the basis of glycemic control and tolerability, up to a maximum of 2000 mg once daily with the evening meal. • If glycemic control is not achieved with metformin hydrochloride extended-release tablets 2000 mg once daily, consider a trial of metformin hydrochloride extended-release tablets 1000 mg twice daily. • Patients receiving metformin hydrochloride (HCl) may be switched to metformin hydrochloride extended-release tablets once daily at the same total daily dose, up to 2000 mg once daily. 2.2 Recommendations for Use in Renal Impairment • Assess renal function prior to initiation of metformin hydrochloride extended-release tablets and periodically thereafter. • Metformin hydrochloride extended-release tablets are contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m 2 • Initiation of metformin hydrochloride extended-release tablets in patients with an eGFR between 30 to 45 mL/minute/1.73 m 2 is not recommended. • In patients taking metformin hydrochloride extended-release tablets whose eGFR later falls below 45 mL/min/1.73 m 2 , assess the benefit risk of continuing therapy. • Discontinue metformin hydrochloride extended-release tablets if the patient’s eGFR later falls below 30 mL/minute/1.73 m 2 [ see Contraindications (4) and Warnings and Precautions (5.1) ]. 2.3 Discontinuation for Iodinated Contrast Imaging Procedures Discontinue metformin hydrochloride extended-release tablets 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 m 2 ; 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 extended-release tablets if renal function is stable.
Warnings & Precautions
• Lactic Acidosis: See boxed warning ( 5.1 ) • Vitamin B 12 Deficiency: Metformin may lower vitamin B 12 levels. Measure hematological parameters annually and vitamin B 12 at 2 to 3 year intervals and manage any abnormalities ( 5.2 ) • Hypoglycemia with Concomitant Use with Insulin and Insulin Secretagogues: Increased risk of hypoglycemia when used in combination with insulin and/or an insulin secretagogue. Lower dose of insulin or insulin secretagogue may be required ( 5.3 ) 5.1 Lactic Acidosis 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 extended-release tablets. In metformin hydrochloride extended-release tablet 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 extended-release tablets 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 (2.2) , Clinical Pharmacology (12.3) ]: o Before initiating metformin hydrochloride extended-release tablets, obtain an estimated glomerular filtration rate (eGFR). o Metformin hydrochloride extended-release tablets are contraindicated in patients with an eGFR less than 30 mL/min/1.73 m 2 [see Contraindications (4) ]. o Initiation of metformin hydrochloride extended-release tablets is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m 2 . o Obtain an eGFR at least annually in all patients taking metformin hydrochloride extended-release tablets. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently. o In patients taking metformin hydrochloride extended-release tablets whose eGFR falls below 45 mL/min/1.73 m 2 , assess the benefit and risk of continuing therapy. • Drug interactions — The concomitant use of metformin hydrochloride extended-release tablets 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 [see Drug Interactions (7) ] . Consider more frequent monitoring of patients. • 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 extended-release tablets 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 m 2 ; 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 extended-release tablets 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 extended-release tablets 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 extended-release tablets. • Excessive alcohol intake — Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving metformin hydrochloride extended-release tablets. • 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 extended-release tablets in patients with clinical or laboratory evidence of hepatic disease. 5.2 Vitamin B 12 Deficiency In clinical trials of 29-week duration with metformin hydrochloride tablets, a decrease to subnormal levels of previously normal serum vitamin B 12 levels was observed in approximately 7% of patients. Such decrease, possibly due to interference with B 12 absorption from the B 12 -intrinsic factor complex, may be associated with anemia but appears to be rapidly reversible with discontinuation of metformin or vitamin B 12 supplementation. Certain individuals (those with inadequate vitamin B 12 or calcium intake or absorption) appear to be predisposed to developing subnormal vitamin B 12 levels. Measure hematologic parameters on an annual basis and vitamin B 12 at 2 to 3 year intervals in patients on metformin hydrochloride extended-release tablets and manage any abnormalities [ see Adverse Reactions (6.1) ]. 5.3 Hypoglycemia with Concomitant Use with Insulin and Insulin Secretagogues Insulin and insulin secretagogues (e.g., sulfonylurea) are known to cause hypoglycemia. Metformin hydrochloride extended-release tablets may increase the risk of hypoglycemia when combined with insulin and/or an insulin secretagogue. Therefore, a lower dose of insulin or insulin secretagogue may be required to minimize the risk of hypoglycemia when used in combination with metformin hydrochloride extended-release tablets [ see Drug Interactions (7) ]. 5.4 Macrovascular Outcomes There have been no clinical studies establishing conclusive evidence of macrovascular risk reduction with metformin hydrochloride extended-release tablets.
Boxed Warning
LACTIC ACIDOSIS Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset of metformin-associated lactic acidosis is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, somnolence, and abdominal pain. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels (> 5 mmol/Liter), anion gap acidosis (without evidence of ketonuria or ketonemia), an increased lactate/pyruvate ratio; and metformin plasma levels generally > 5 mcg/mL [ see Warnings and Precautions (5.1) ]. Risk factors for metformin-associated lactic acidosis include renal impairment, concomitant use of certain drugs (e.g., carbonic anhydrase inhibitors such as topiramate), age 65 years old or greater, having a radiological study with contrast, surgery and other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, and hepatic impairment. Steps to reduce the risk of and manage metformin-associated lactic acidosis in these high risk groups are provided [ see Dosage and Administration (2.2) , Contraindications (4) , Warnings and Precautions (5.1) ]. If metformin-associated lactic acidosis is suspected, immediately discontinue metformin hydrochloride extended-release tablets and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended [ see Warnings and Precautions (5.1) ]. WARNING: LACTIC ACIDOSIS See full prescribing information for complete boxed warning. • Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Symptoms included malaise, myalgias, respiratory distress, somnolence, and abdominal pain. Laboratory abnormalities included elevated blood lactate levels, anion gap acidosis, increased lactate/pyruvate ratio; and metformin plasma levels generally > 5 mcg/mL. ( 5.1 ) • Risk factors include renal impairment, concomitant use of certain drugs, age > 65 years old, radiological studies with contrast, surgery and other procedures, hypoxic states, excessive alcohol intake, and hepatic impairment. Steps to reduce the risk of and manage metformin- associated lactic acidosis in these high risk groups are provided in the Full Prescribing Information. ( 5.1 ) • If lactic acidosis is suspected, discontinue metformin hydrochloride extended-release tablets and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended. ( 5.1 )
Contraindications
Metformin hydrochloride extended-release tablets are contraindicated in patients with: • Severe renal impairment (eGFR below 30 mL/min/1.73 m 2 ) [ see Warnings and Precautions (5.1) ]. • 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 m 2 ) ( 4 , 5.1 ) • Hypersensitivity to metformin ( 4 ) • Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma ( 4 )
Adverse Reactions
The following adverse reactions are also discussed elsewhere in the labeling: • Lactic Acidosis [ see Boxed Warning and Warnings and Precautions (5.1) ] • Vitamin B 12 Deficiency [ see Warnings and Precautions (5.2) ] • Hypoglycemia [ see Warnings and Precautions (5.3) ] Common adverse reactions are diarrhea, nausea/vomiting, abdominal pain, constipation, abdomen distention, dyspepsia/heartburn, flatulence, dizziness, headache, upper respiratory infection, taste disturbance ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Studies Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. In placebo-controlled trials, 781 patients were administered metformin hydrochloride extended-release tablets. Adverse reactions reported in greater than 5% of the patients treated with metformin hydrochloride extended-release tablets and that were more common than in placebo-treated patients are listed in Table 1. Table 1: Adverse Reactions from Clinical Trials of Metformin Hydrochloride Extended-Release Tablets Occurring > 5% and More Common than Placebo in Patients with Type 2 Diabetes Mellitus Adverse Reaction Metformin Hydrochloride Extended-Release Tablets (n = 781) Placebo (n = 195) Diarrhea 10% 3% Nausea/Vomiting 7% 2% Diarrhea led to the discontinuation of metformin hydrochloride extended-release tablets in 0.6% of patients. Additionally, the following adverse reactions were reported in 1.0% to 5.0% of patients treated with metformin hydrochloride extended-release tablets and were more commonly reported than in placebo-treated patients: abdominal pain, constipation, abdomen distention, dyspepsia/heartburn, flatulence, dizziness, headache, upper respiratory infection, taste disturbance. Laboratory Tests Vitamin B 12 Concentrations In clinical trials of 29-week duration with metformin hydrochloride tablets, a decrease to subnormal levels of previously normal serum vitamin B 12 levels was observed in approximately 7% of patients. 6.2 Postmarketing Experience The following adverse reactions have been identified during post approval use of metformin. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Cholestatic, hepatocellular, and mixed hepatocellular liver injury have been reported with postmarketing use of metformin.
Drug Interactions
Table 2 presents clinically significant drug interactions with metformin hydrochloride extended-release tablets. Table 2: Clinically Significant Drug Interactions with Metformin Hydrochloride Extended-Release Tablets Carbonic Anhydrase Inhibitors Clinical Impact: Carbonic anhydrase inhibitors frequently cause a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Concomitant use of these drugs with metformin hydrochloride extended-release tablets may increase the risk for lactic acidosis. Intervention: Consider more frequent monitoring of these patients. Examples: Topiramate, zonisamide, acetazolamide or dichlorphenamide. Drugs that Reduce Metformin Clearance Clinical Impact: Concomitant use of drugs that interfere with common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE] inhibitors) could increase systemic exposure to metformin and may increase the risk for lactic acidosis [see Clinical Pharmacology (12.3) ]. Intervention: Consider the benefits and risks of concomitant use with metformin hydrochloride extended-release tablets. Examples: Ranolazine, vandetanib, dolutegravir, and cimetidine. Alcohol Clinical Impact: Alcohol is known to potentiate the effect of metformin on lactate metabolism. Intervention: Warn patients against excessive alcohol intake while receiving metformin hydrochloride extended-release tablets. Insulin Secretagogues or Insulin Clinical Impact: Coadministration of metformin hydrochloride extended-release tablets with an insulin secretagogue (e.g., sulfonylurea) or insulin may increase the risk of hypoglycemia. Intervention: Patients receiving an insulin secretagogue or insulin may require lower doses of the insulin secretagogue or insulin. Drugs Affecting Glycemic Control Clinical Impact: Certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control. Intervention: When such drugs are administered to a patient receiving metformin hydrochloride extended-release tablets, observe the patient closely for loss of blood glucose control. When such drugs are withdrawn from a patient receiving metformin hydrochloride extended-release tablets, observe the patient closely for hypoglycemia. Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid. • Carbonic anhydrase inhibitors may increase risk of lactic acidosis. Consider more frequent monitoring ( 7 ) • Drugs that reduce metformin clearance (such as ranolazine, vandetanib, dolutegravir, and cimetidine) may increase the accumulation of metformin. Consider the benefits and risks of concomitant use ( 7 ) • Alcohol can potentiate the effect of metformin on lactate metabolism. Warn patients against excessive alcohol intake ( 7 ) Drug Interactions In Vivo Assessment of Drug Interactions Table 5: Effect of Coadministered Drug on Plasma Metformin Systemic Exposure Coadministered Drug Dose of Coadministered Drug All metformin hydrochloride and coadministered drugs were given as single doses Dose of Metformin Hydrochloride Geometric Mean Ratio (ratio with/without coadministered drug) No Effect = 1.00 AUC AUC = AUC inf C max No dosing adjustments required for the following: Glyburide 5 mg 850 mg metformin 0.91 Ratio of arithmetic means 0.93 Furosemide 40 mg 850 mg metformin 1.09 1.22 Nifedipine 10 mg 850 mg metformin 1.16 1.21 Propranolol 40 mg 850 mg metformin 0.90 0.94 Ibuprofen 400 mg 850 mg metformin 1.05 1.07 Cationic drugs eliminated by renal tubular secretion may reduce metformin elimination [ See Warnings and Precautions (5.1) and Drug Interactions (7) . ] Cimetidine 400 mg 850 mg metformin 1.40 1.61 Carbonic anhydrase inhibitors may cause metabolic acidosis [ See Warnings and Precautions (5.1) and Drug Interactions (7) .] Topiramate 5 mg At steady state with topiramate 100 mg every 12 hours and metformin 500 mg every 12 hours; AUC = AUC 0-12h 5 mg metformin 1.25 1.17 Table 6: Effect of Metformin on Coadministered Drug Systemic Exposure Coadministered Drug Dose of Coadministered Drug All metformin hydrochloride and coadministered drugs were given as single doses Dose of Metformin Hydrochloride Geometric Mean Ratio (ratio with/without coadministered drug) No Effect = 1.00 AUC AUC = AUC inf unless otherwise noted C max No dosing adjustments required for the following: Glyburide 5 mg 850 mg glyburide 0.78 Ratio of arithmetic means, p-value of difference < 0.05 0.63 Furosemide 40 mg 850 mg furosemide 0.87 0.69 Nifedipine 10 mg 850 mg nifedipine 1.10 AUC 0-24hr reported 1.08 Propranolol 40 mg 850 mg propranolol 1.01 1.02 Ibuprofen 400 mg 850 mg ibuprofen 0.97 Ratio of arithmetic means 1.01 Cimetidine 400 mg 850 mg cimetidine 0.95 1.01
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