Metformin Drug Information

Metformin hydrochloride tablets are 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. Metformin hydrochloride tablets are biguanide 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.

m 2 Initiation is not recommended in patients with eGFR between 30

to 45 mL/minute/

m 2 Assess risk/benefit of continuing if eGFR falls below 45 mL/minute/1.73

m 2 Discontinue if eGFR falls below 30 mL/minute/

m 2 2.1 Adult Dosage Metformin Hydrochloride Tablets

The recommended starting dose of metformin hydrochloride tablets are 500 mg orally twice a day or 850 mg once a day, given with meals. Increase the dose in increments of 500 mg weekly or 850 mg every 2 weeks on the basis of glycemic control and tolerability, up to a maximum dose of 2550 mg per day, given in divided doses. Doses above 2000 mg may be better tolerated given 3 times a day with meals.

Pediatric Dosage for metformin hydrochloride tablets

The recommended starting dose of metformin hydrochloride tablets for pediatric patients 10 years of age and older is 500 mg orally twice a day, given with meals. Increase dosage in increments of 500 mg weekly on the basis of glycemic control and tolerability, up to a maximum of 2000 mg per day, given in divided doses twice daily.

Recommendations for Use in Renal Impairment Assess renal function prior to initiation

of metformin hydrochloride tablets and periodically thereafter. Metformin hydrochloride tablets are contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/

m 2. Initiation of metformin hydrochloride tablets in patients with an eGFR

between 30 to 45 mL/minute/

m 2 is not recommended.

In patients taking metformin hydrochloride tablets whose eGFR later falls below 45 mL/min/

m 2, assess the benefit risk of continuing therapy. Discontinue metformin hydrochloride

tablets if the patient’s eGFR later falls below 30 mL/minute/

m 2 . 2.4 Discontinuation for Iodinated Contrast Imaging Procedures Discontinue metformin

hydrochloride tablets at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/

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 tablets if renal function is stable.

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. Metformin Hydrochloride Tablets In a U.S. clinical trial of metformin hydrochloride tablets in patients with type 2 diabetes mellitus, a total of 141 patients received metformin hydrochloride tablets up to 2550 mg per day. Adverse reactions reported in greater than 5% of metformin hydrochloride tablets treated patients and that were more common than in placebo-treated patients, are listed in Table 1. Table 1: Adverse Reactions from a Clinical Trial of Metformin Hydrochloride Tablets Occurring >5% and More Common than Placebo in Patients with Type 2 Diabetes Mellitus Metformin Hydrochloride Tablets (n=141) Placebo (n=145) Diarrhea 53% 12% Nausea/Vomiting 26% 8% Flatulence 12% 6% Asthenia 9% 6% Indigestion 7% 4% Abdominal Discomfort 6% 5% Headache 6% 5% Diarrhea led to discontinuation of metformin hydrochloride tablets in 6% of patients.

Additionally, the following adverse reactions were reported in ≥1 % to ≤5% of metformin hydrochloride tablets treated patients and were more commonly reported with metformin hydrochloride tablets than placebo: abnormal stools, hypoglycemia, myalgia, lightheaded, dyspnea, nail disorder, rash, sweating increased, taste disorder, chest discomfort, chills, flu syndrome, flushing, palpitation. In metformin hydrochloride tablets clinical trials of 29-week duration, a decrease to subnormal levels of previously normal serum vitamin B 12 levels was observed in approximately 7% of patients. Pediatric Patients In clinical trials with metformin hydrochloride tablets in pediatric patients with type 2 diabetes mellitus, the profile of adverse reactions was similar to that observed in adults.

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.

• Table 3 presents clinically significant drug interactions with metformin hydrochloride tablets.
• Table 3: Clinically Significant Drug Interactions with Metformin Hydrochloride 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 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 tablet 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 / multidrug and toxin extrusion inhibitors) could increase systemic exposure to metformin and may increase the risk for lactic acidosis.
• Intervention: Consider the benefits and risks of concomitant use with metformin hydrochloride 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 tablets.
• Insulin Secretagogues or Insulin Clinical Impact: Coadministration of metformin hydrochloride 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 tablets, observe the patient closely for loss of blood glucose control. When such drugs are withdrawn from a patient receiving metformin hydrochloride 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 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 Alcohol can potentiate the effect of metformin on lactate metabolism. Warn patients against excessive alcohol intake

Pregnancy Risk Summary Limited data with metformin hydrochloride 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 . There are risks to the mother and fetus associated with poorly controlled diabetes mellitus in pregnancy . 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 2- and 5-times, respectively, a 2550 mg clinical dose, based on body surface area . The estimated background risk of major birth defects is 6 to 10% in women with pre-gestational diabetes mellitus with an HbA1C >7 and has been reported to be as high as 20 to 25% in women with a 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 to 4% and 15 to 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 post-marketing 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 hydrochloride did not adversely affect development outcomes when administered to pregnant rats and rabbits at doses up to 600 mg/kg/day. This represents an exposure of about 2 and 5 times a 2550 mg clinical dose based on body surface area comparisons for rats and rabbits, respectively.

Determination of fetal concentrations demonstrated a partial placental barrier to metformin.

Pediatric Use Metformin Hydrochloride Tablets The safety and effectiveness of metformin hydrochloride tablets for the treatment of type 2 diabetes mellitus have been established in pediatric patients 10 to 16 years old. Safety and effectiveness of metformin hydrochloride tablets have not been established in pediatric patients less than 10 years old. Use of metformin hydrochloride tablets in pediatric patients 10 to 16 years old for the treatment of type 2 diabetes mellitus is supported by evidence from adequate and well-controlled studies of metformin hydrochloride tablets in adults with additional data from a controlled clinical study in pediatric patients 10 to 16 years old with type 2 diabetes mellitus, which demonstrated a similar response in glycemic control to that seen in adults . In this study, adverse reactions were similar to those described in adults.

A maximum daily dose of 2000 mg of metformin hydrochloride tablets is recommended..

m 2 ). Hypersensitivity to metformin. Acute or chronic metabolic acidosis, including

diabetic ketoacidosis, with or without coma. Severe renal impairment (eGFR below 30 mL/min/

m 2 ) Hypersensitivity to metformin Acute or chronic metabolic acidosis, including

diabetic ketoacidosis, with or without coma.

Overdose of metformin hydrochloride has occurred, including ingestion of amounts greater than 50 grams. Hypoglycemia was reported in approximately 10% of cases, but no causal association with metformin has been established. Lactic acidosis has been reported in approximately 32% of metformin overdose cases . Metformin is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions.

Therefore, hemodialysis may be useful for removal of accumulated drug from patients in whom metformin overdosage is suspected.