Metformin Hydrochloride

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 )

Metformin Hydrochloride Extended-Release Tablets are available as: Extended-release tablets: 500 mg white, film-coated, oval-shaped tablets with “M500” on one side. Extended-release tablets : 1,000 mg white, film-coated, oval-shaped tablets with “M1000” on one side. Metformin Hydrochloride Extended-Release Tablets: 500 mg and 1,000 mg ( 3 )

Metformin Hydrochloride Extended-Release Tablets are contraindicated in patients with: Severe renal impairment (eGFR below 30 mL/minute/1.73 m 2 ) [see Warnings and Precautions ( 5.1 )] . Known hypersensitivity to metformin. Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma. Severe renal impairment: (eGFR below 30 mL/minute/1.73 m 2 ) ( 4 , 5.1 ) Known hypersensitivity to metformin ( 4 ) Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma ( 4 )

Lactic Acidosis : See boxed warning. ( 5.1 ) Vitamin B 12 Deficiency : Metformin may lower vitamin B 12 levels. Monitor 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, hypothermia, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. Metformin-associated lactic acidosis was characterized by elevated blood lactate concentrations (>5 mmol/Liter), 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 Tablets-treated patients with a diagnosis or strong suspicion of lactic acidosis, prompt hemodialysis is recommended to correct the acidosis and remove accumulated metformin (metformin HCl is dialyzable, with a clearance of up to 170 mL/minute 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 ) and Clinical Pharmacology ( 12.3 )]: Before initiating Metformin Hydrochloride Extended-Release Tablets, obtain an estimated glomerular filtration rate (eGFR). Metformin Hydrochloride Extended-Release Tablets are contraindicated in patients with an eGFR less than 30 mL/minute/1.73 m 2 [see Contraindications ( 4 )]. Initiation of Metformin Hydrochloride Extended-Release Tablets is not recommended in patients with eGFR between 30 to 45 mL/minute/1.73 m 2 . Obtain an eGFR at least annually in all patients taking Metformin Hydrochloride Extended-Release Tablets. In patients at increased risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently. In patients taking Metformin Hydrochloride Extended-Release Tablets whose eGFR later falls below 45 mL/minute/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 )]. Therefore, 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 [see Use in Specific Populations ( 8.5 )]. Radiological 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/minute/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 also cause prerenal azotemia. When such events occur, discontinue Metformin Hydrochloride Extended-Release Tablets. Excessive Alcohol Intake: Alcohol potentiates the effect of metformin on lactate metabolism, and this may increase the risk of metformin-associated lactic acidosis. Warn patients 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 HCl 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 )] . […]

The following adverse reactions are discussed in more detail in other sections of 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 )] Adverse reactions occurring >5% in Metformin Hydrochloride Extended-Release Tablets clinical trials: hypoglycemia, diarrhea, and nausea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Oceanside Pharmaceuticals at 1-800-321-4576 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

6.1 Clinical Trials 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 clinical trials conducted in the U.S., over 1,000 patients with type 2 diabetes mellitus have been treated with Metformin Hydrochloride Extended-Release Tablets 1,500 to 2,000 mg/day in active-controlled and placebo-controlled studies with the 500 mg dosage form. In the add-on to sulfonylurea study, patients receiving background glyburide therapy were randomized to receive add-on treatment of either one of three different regimens of Metformin Hydrochloride Extended-Release Tablets or placebo. In total, 431 patients received Metformin Hydrochloride Extended-Release Tablets and glyburide and 144 patients received placebo and glyburide. Adverse reactions reported in greater than 5% of patients treated with Metformin Hydrochloride Extended-Release Tablets that were more common in the combined Metformin Hydrochloride Extended-Release Tablets and glyburide group than in the placebo and glyburide group are shown in Table 1. In 0.7% of patients treated with Metformin Hydrochloride Extended-Release Tablets and glyburide, diarrhea was responsible for discontinuation of study medication compared to no patients in the placebo and glyburide group. Table 1: Adverse Reactions Reported by >5% Adverse reactions that were more common in the Metformin Hydrochloride Extended-Release Tablets-treated than in the placebo-treated patients. of Patients for the Combined Metformin Hydrochloride Extended-Release Tablets Groups Versus Placebo Group Adverse Reaction Metformin Hydrochloride Extended-Release Tablets + Glyburide (n=431) Placebo + Glyburide (n=144) Hypoglycemia 14% 5% Diarrhea 13% 6% Nausea 7% 4% Laboratory Tests Vitamin B 12 Concentrations In clinical trials of 29-week duration with metformin HCl 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 Hydrochloride Extended-Release Tablets. 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.

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 Hydrochloride Extended-Release Tablets 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 )

Females and Males of Reproductive Potential: Advise premenopausal females of the potential for an unintended pregnancy. ( 8.3 ) Geriatric Use: Assess renal function more frequently. ( 8.5 ) Hepatic Impairment: Avoid use in patients with hepatic impairment. ( 8.7 )

8.1 Pregnancy Risk Summary Limited data with Metformin Hydrochloride Extended-Release Tablets in pregnant women are not sufficient to determine a drug-associated risk for major birth defects or miscarriage. Published studies with metformin use during pregnancy have not reported a clear association with metformin and major birth defect or miscarriage risk [see Data]. There are risks to the mother and fetus associated with poorly controlled diabetes mellitus in pregnancy [see Clinical Considerations] . No adverse developmental effects were observed when metformin was administered to pregnant Sprague Dawley rats and rabbits during the period of organogenesis at doses up to 3 and 1 times, respectively, a 2,000 mg clinical dose, based on body surface area [see Data] . The estimated background risk of major birth defects is 6–10% in women with pregestational diabetes mellitus with an HbA1c >7 and has been reported to be as high as 20–25% in women with an HbA1c >10. The estimated background risk of miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2–4% and 15–20%, respectively. Clinical Considerations Disease-associated maternal and/or embryo/fetal risk Poorly controlled diabetes mellitus in pregnancy increases the maternal risk for diabetic ketoacidosis, pre-eclampsia, spontaneous abortions, preterm delivery, stillbirth and delivery complications. Poorly controlled diabetes mellitus increases the fetal risk for major birth defects, stillbirth, and macrosomia-related morbidity. Data Human Data Published data from postmarketing studies have not reported a clear association with metformin and major birth defects, miscarriage, or adverse maternal or fetal outcomes when metformin was used during pregnancy. However, these studies cannot definitely establish the absence of any metformin-associated risk because of methodological limitations, including small sample size and inconsistent comparator groups. Animal Data Metformin HCl was not teratogenic or embyrolethal when administered to rats prior to pregnancy through the period of organogenesis at doses up to 900 mg/kg, or when administered to rabbits during the period of organogenesis at doses up to 90 mg/kg.

8.2 Lactation Risk Summary Limited published studies report that metformin is present in human milk [see Data] . However, there is insufficient information to determine the effects of metformin on the breastfed infant and no available information on the effects of metformin on milk production. Therefore, the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for Metformin Hydrochloride Extended-Release Tablets and any potential adverse effects on the breastfed child from Metformin Hydrochloride Extended-Release Tablets or from the underlying maternal condition. Data Published clinical lactation studies report that metformin is present in human milk which resulted in infant doses approximately 0.11% to 1% of the maternal weight-adjusted dosage and a milk/plasma ratio ranging between 0.13 and 1. However, the studies were not designed to definitely establish the risk of use of metformin during lactation because of small sample size and limited adverse event data collected in infants.

8.3 Females and Males of Reproductive Potential Discuss the potential for unintended pregnancy with premenopausal women as therapy with Metformin Hydrochloride Extended-Release Tablets may result in ovulation in some anovulatory women.

8.4 Pediatric Use Safety and effectiveness of Metformin Hydrochloride Extended-Release Tablets in pediatric patients have not been established.

8.5 Geriatric Use Clinical studies of Metformin Hydrochloride Extended-Release Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. 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 Dosage and Administration ( 2.2 ) and Warnings and Precautions ( 5.1 ).]

8.6 Renal Impairment Metformin is substantially excreted by the kidney, and the risk of metformin accumulation and lactic acidosis increases with the degree of renal impairment. Metformin Hydrochloride Extended-Release Tablets are contraindicated in severe renal impairment, patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m 2 . [see Dosage and Administration ( 2.2 ), Contraindications ( 4 ), Warnings and Precautions ( 5.1 ), and Clinical Pharmacology ( 12.3 ).]

8.7 Hepatic Impairment Use of metformin in patients with hepatic impairment has been associated with some cases of lactic acidosis. Metformin Hydrochloride Extended-Release Tablets are not recommended in patients with hepatic impairment . [see Warnings and Precautions ( 5.1 ).]

Metformin is a biguanide that improves glucose tolerance in patients with type 2 diabetes, lowering both basal and postprandial plasma glucose. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. With metformin therapy, insulin secretion remains unchanged while fasting insulin levels and day-long plasma insulin response may decrease.