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Metformin ER 500mg Osmotic Tabs

Manufacturer MYLAN Active Ingredient Metformin Extended-Release Tablets(met FOR min) Pronunciation met-FOR-min
WARNING: Rarely, metformin may cause too much lactic acid in the blood (lactic acidosis). The risk is higher in people who have kidney problems, liver problems, heart failure, use alcohol, or take certain other drugs, including topiramate. The risk is also higher in people who are 65 or older and in people who are having surgery, an exam or test with contrast, or other procedures. If lactic acidosis happens, it can lead to other health problems and can be deadly. Kidney tests may be done while taking this drug.Do not take this drug if you have a very bad infection, low oxygen, or a lot of fluid loss (dehydration).Call your doctor right away if you have signs of too much lactic acid in the blood (lactic acidosis) like confusion; fast breathing; fast or slow heartbeat; a heartbeat that does not feel normal; very bad stomach pain, upset stomach, or throwing up; feeling very sleepy; shortness of breath; feeling very tired or weak; very bad dizziness; feeling cold; or muscle pain or cramps. @ COMMON USES: It is used to lower blood sugar in patients with high blood sugar (diabetes).
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Drug Class
Antidiabetic agent
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Pharmacologic Class
Biguanide
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Pregnancy Category
Not available
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FDA Approved
Oct 2000
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DEA Schedule
Not Controlled

Overview

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What is this medicine?

Metformin ER is a medicine used to help control high blood sugar levels in people with type 2 diabetes. It works by helping your body use insulin more effectively, reducing the amount of sugar your liver makes, and decreasing the amount of sugar your body absorbs from food. The 'ER' means Extended-Release, so it releases the medicine slowly over time, allowing you to take it less often.
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How to Use This Medicine

Taking Your Medication Correctly

To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. Take your medication with meals to help your body absorb it properly. Even if you start to feel better, continue taking your medication as directed by your doctor or healthcare provider.

If you are taking your medication once daily, take it with your evening meal. Swallow the tablet whole - do not chew, break, or crush it. If you have difficulty swallowing, consult with your doctor for guidance.

Storing and Disposing of Your Medication

To maintain the effectiveness and safety of your medication, store it at room temperature, protected from light and moisture. Keep it in a dry place, away from the bathroom. Ensure that all medications are kept in a secure location, out of the reach of children and pets.

What to Do If You Miss a Dose

If you miss a dose, skip it and resume your regular dosing schedule unless your doctor advises you to do otherwise. Do not take two doses at the same time or take extra doses to make up for the missed one.
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Lifestyle & Tips

  • Take Metformin ER with your evening meal to help reduce stomach upset and improve absorption.
  • Swallow the tablet whole; do not crush, chew, or break it, as this will affect its extended-release properties.
  • Follow a healthy diet plan as recommended by your doctor or dietitian.
  • Engage in regular physical activity as advised by your healthcare provider.
  • Limit alcohol intake, as excessive alcohol can increase the risk of a serious side effect called lactic acidosis.
  • Stay well-hydrated, especially during illness, exercise, or hot weather.
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Available Forms & Alternatives

Available Strengths:

Dosing & Administration

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Adult Dosing

Standard Dose: Initial: 500 mg ER orally once daily with the evening meal. Titrate gradually.
Dose Range: 500 - 2500 mg

Condition-Specific Dosing:

Type 2 Diabetes Mellitus: Initial: 500 mg ER orally once daily with the evening meal. Increase dose by 500 mg weekly to a maximum of 2000 mg once daily. If glycemic control is not achieved, consider 1000 mg twice daily. Max dose 2500 mg/day (some formulations).
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Pediatric Dosing

Neonatal: Not established
Infant: Not established
Child: Not established for ER formulation under 10 years. For children 10-16 years with Type 2 Diabetes: Initial 500 mg ER orally once daily with evening meal. Titrate by 500 mg weekly to a maximum of 2000 mg once daily.
Adolescent: Initial 500 mg ER orally once daily with evening meal. Titrate by 500 mg weekly to a maximum of 2000 mg once daily.
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Dose Adjustments

Renal Impairment:

Mild: eGFR 60-89 mL/min/1.73m²: No dose adjustment needed. Monitor eGFR annually.
Moderate: eGFR 45-59 mL/min/1.73m²: Not recommended to initiate. If already on metformin, reduce dose by 50% or discontinue if eGFR falls below 45. Monitor eGFR every 3-6 months. eGFR 30-44 mL/min/1.73m²: Not recommended to initiate. If already on metformin, discontinue. Monitor eGFR every 3 months.
Severe: eGFR < 30 mL/min/1.73m²: Contraindicated.
Dialysis: Contraindicated in patients undergoing dialysis due to increased risk of lactic acidosis.

Hepatic Impairment:

Mild: Use with caution. Increased risk of lactic acidosis.
Moderate: Generally avoided due to increased risk of lactic acidosis.
Severe: Contraindicated due to increased risk of lactic acidosis.

Pharmacology

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Mechanism of Action

Metformin is a biguanide that improves glucose tolerance in patients with type 2 diabetes by lowering both basal and postprandial plasma glucose. Its primary mechanism of action is to decrease hepatic glucose production. It also decreases intestinal absorption of glucose and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. Metformin does not stimulate insulin secretion and, therefore, does not cause hypoglycemia in monotherapy.
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Pharmacokinetics

Absorption:

Bioavailability: Approximately 50-60% (for immediate release, ER may vary slightly)
Tmax: 7-8 hours (for ER formulation)
FoodEffect: Food decreases the extent of absorption and slightly prolongs Tmax for ER formulations, but it is recommended to take with food to improve gastrointestinal tolerability.

Distribution:

Vd: 654 ± 358 L (for immediate release)
ProteinBinding: < 5%
CnssPenetration: Limited

Elimination:

HalfLife: Approximately 6.2 hours (plasma); 17.6 hours (blood)
Clearance: Renal clearance is approximately 3.5 times greater than creatinine clearance, indicating tubular secretion.
ExcretionRoute: Renal (primarily unchanged in urine)
Unchanged: > 90%
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Pharmacodynamics

OnsetOfAction: Days to weeks for full therapeutic effect
PeakEffect: Typically seen after several weeks of consistent dosing and titration.
DurationOfAction: Approximately 24 hours for ER formulation (allows once-daily dosing)
Confidence: High

Safety & Warnings

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BLACK BOX WARNING

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 distress. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels (>5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate/pyruvate ratio; metformin plasma levels generally >5 mcg/mL. If metformin-associated lactic acidosis is suspected, discontinue metformin and institute general supportive measures promptly in a hospital setting. Prompt hemodialysis is recommended. Risk factors include renal impairment, concomitant use of certain drugs (e.g., carbonic anhydrase inhibitors), age 65 years 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.
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Side Effects

Urgent Side Effects: Seek Medical Help Right Away

Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
 Stomach problems that occur later during treatment, which may be a sign of lactic acidosis (an acid health problem in the blood)
Low blood sugar, which may be more likely when this medication is used with other diabetes drugs. Symptoms may include:
+ Dizziness
+ Headache
+ Feeling sleepy or weak
+ Shaking
+ Fast heartbeat
+ Confusion
+ Hunger
+ Sweating

If you experience low blood sugar, follow your doctor's instructions for treatment, which may include taking glucose tablets, liquid glucose, or some fruit juices.

Other Possible Side Effects

Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. Contact your doctor or seek medical help if you experience any of the following side effects or if they bother you or do not go away:

 Stomach pain or heartburn
Gas
 Diarrhea, upset stomach, or vomiting
Feeling tired or weak
 Headache

This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
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Seek Immediate Medical Attention If You Experience:

  • **Symptoms of Lactic Acidosis (SERIOUS, seek immediate medical attention):** unusual muscle pain, trouble breathing, unusual sleepiness, stomach pain, nausea, vomiting, diarrhea, feeling cold, dizziness, lightheadedness, slow or irregular heartbeat.
  • **Symptoms of Vitamin B12 Deficiency (report to doctor):** unusual tiredness, weakness, numbness or tingling in hands or feet, sore tongue, memory problems.
  • **Common side effects (usually mild and temporary):** diarrhea, nausea, vomiting, stomach upset, gas, metallic taste in mouth. These often improve over time.
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Before Using This Medicine

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reaction you experienced, including the symptoms that occurred.
 Certain health conditions, including:
+ Acidic blood problems
+ Kidney disease
+ Liver disease
Recent medical events, such as a heart attack or stroke
 Any difficulties with eating or drinking, including situations where you may be required to fast before a procedure or surgery

Additionally, if you are scheduled to undergo an exam or test that involves contrast agents, or have had one within the past 48 hours, discuss this with your doctor.

This medication can interact with other substances, so it is crucial to provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
 Natural products and vitamins you are using
* Any health problems you have

Before starting, stopping, or changing the dose of any medication, including this one, consult with your doctor to ensure your safety. Verify that it is safe to take this medication with all your other medications and health conditions.
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Precautions & Cautions

It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Before consuming alcohol, discuss the potential risks with your doctor.

If you experience low blood sugar, avoid driving, as it increases the risk of accidents. Monitor your blood sugar levels as directed by your doctor. Regular blood tests, as advised by your doctor, are also crucial to ensure the medication's effectiveness and safety.

During stressful periods, such as illness, infection, injury, or surgery, your blood sugar levels may be more challenging to control. Changes in physical activity, exercise, or diet can also impact your blood sugar levels. Adhere to the diet and exercise plan recommended by your doctor to maintain optimal blood sugar control.

If you experience diarrhea or vomiting, contact your doctor promptly, as you may need to increase fluid intake to prevent dehydration. In hot weather or during intense physical activity, drink plenty of fluids to avoid fluid loss.

Long-term treatment with metformin may lead to a decrease in vitamin B-12 levels. If you have a history of low vitamin B-12 levels, consult your doctor. You may notice the appearance of the tablet in your stool, but this is a normal occurrence and not a cause for concern. If you have any questions or concerns, discuss them with your doctor.

If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects. Women of childbearing age who have not been ovulating may experience a return of fertility while taking this medication. To avoid pregnancy, use birth control measures while taking this drug.

If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor. It is crucial to discuss the potential benefits and risks of this medication to both you and your baby.
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Overdose Information

Overdose Symptoms:

  • Lactic acidosis (most serious concern, see symptoms above)
  • Hypoglycemia (low blood sugar), especially if taken with other antidiabetic agents or alcohol
  • Severe gastrointestinal upset

What to Do:

In case of suspected overdose, seek immediate medical attention or call a poison control center (1-800-222-1222). Treatment for lactic acidosis involves immediate discontinuation of metformin, general supportive measures, and prompt hemodialysis to correct acidosis and remove metformin.

Drug Interactions

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Contraindicated Interactions

  • Iodinated contrast media (hold metformin at time of or prior to procedure and for 48 hours after, re-evaluate renal function before restarting)
  • Alcohol (acute or chronic excessive intake due to increased risk of lactic acidosis)
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Major Interactions

  • Carbonic anhydrase inhibitors (e.g., topiramate, zonisamide, acetazolamide, dichlorphenamide) - may increase risk of lactic acidosis.
  • Drugs that reduce metformin clearance (e.g., cimetidine, ranolazine, dolutegravir, isavuconazonium) - may increase metformin levels and risk of lactic acidosis.
  • Drugs that affect renal function (e.g., NSAIDs, ACE inhibitors, ARBs, diuretics) - may increase risk of lactic acidosis by impairing renal clearance of metformin.
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Moderate Interactions

  • Cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, trimethoprim, vancomycin) - may compete for renal tubular transport, potentially increasing metformin levels.
  • Nifedipine - may increase metformin absorption and Cmax.
  • Glucocorticoids, sympathomimetics, diuretics, thyroid products, phenothiazines, estrogens, oral contraceptives, phenytoin, nicotinic acid, calcium channel blockers, isoniazid - may cause hyperglycemia, requiring dose adjustment of metformin.
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Minor Interactions

  • Not specifically categorized as minor, but general caution with any drug affecting glucose levels.

Monitoring

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Baseline Monitoring

Renal function (eGFR)

Rationale: To assess baseline kidney function and determine appropriate dosing, as metformin is renally eliminated and contraindicated in severe renal impairment.

Timing: Prior to initiation of therapy.

HbA1c

Rationale: To establish baseline glycemic control.

Timing: Prior to initiation of therapy.

Vitamin B12 levels

Rationale: To establish baseline levels, as long-term metformin use can be associated with vitamin B12 deficiency.

Timing: Prior to initiation of therapy, especially in patients at risk for deficiency.

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Routine Monitoring

Renal function (eGFR)

Frequency: At least annually; more frequently (e.g., every 3-6 months) in patients at risk for renal impairment (e.g., elderly, those with comorbidities).

Target: > 60 mL/min/1.73m² for full dose; > 45 mL/min/1.73m² for continued use with caution.

Action Threshold: If eGFR falls below 45 mL/min/1.73m², reassess dose; if below 30 mL/min/1.73m², discontinue.

HbA1c

Frequency: Every 3-6 months, or as clinically indicated.

Target: Individualized, typically < 7% for most adults.

Action Threshold: If target not met, consider dose adjustment or addition of other antidiabetic agents.

Blood glucose (fasting and postprandial)

Frequency: Daily or as directed by healthcare provider.

Target: Individualized, e.g., FBG 80-130 mg/dL, PPG < 180 mg/dL.

Action Threshold: Persistent high readings indicate need for dose adjustment or therapy change.

Vitamin B12 levels

Frequency: Periodically, especially in patients on long-term therapy or with symptoms of deficiency (e.g., anemia, neuropathy).

Target: Normal range (e.g., 200-900 pg/mL).

Action Threshold: If low, consider supplementation.

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Symptom Monitoring

  • Symptoms of lactic acidosis: malaise, myalgia, respiratory distress, somnolence, abdominal distress, hypothermia, hypotension, resistant bradyarrhythmias.
  • Symptoms of vitamin B12 deficiency: fatigue, weakness, numbness or tingling, memory problems, glossitis.
  • Gastrointestinal side effects: diarrhea, nausea, vomiting, abdominal bloating, flatulence, anorexia.

Special Patient Groups

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Pregnancy

Metformin crosses the placenta. While insulin is generally preferred for glycemic control in pregnancy, metformin may be considered in some cases, particularly for gestational diabetes or polycystic ovary syndrome (PCOS) related infertility. Data suggest it does not increase the risk of major birth defects. Discuss risks and benefits with your healthcare provider.

Trimester-Specific Risks:

First Trimester: Limited data, but no clear evidence of increased teratogenic risk.
Second Trimester: Generally considered safe for continued use if initiated prior to pregnancy or if benefits outweigh risks.
Third Trimester: Generally considered safe for continued use if initiated prior to pregnancy or if benefits outweigh risks.
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Lactation

Metformin is excreted into breast milk in small amounts. The amount ingested by the infant is generally considered low and unlikely to cause adverse effects in healthy, full-term infants. It is generally considered compatible with breastfeeding. Monitor breastfed infants for signs of hypoglycemia or gastrointestinal upset.

Infant Risk: Low risk (L2)
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Pediatric Use

Approved for children 10 years and older with type 2 diabetes. Renal function should be monitored closely, similar to adults. Gastrointestinal side effects may be prominent.

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Geriatric Use

Use with caution in elderly patients due to increased likelihood of decreased renal function. Renal function should be assessed more frequently. The risk of lactic acidosis increases with age and impaired renal function.

Clinical Information

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Clinical Pearls

  • Metformin ER should be taken with the evening meal to minimize GI side effects and optimize absorption.
  • Patients should be educated on the symptoms of lactic acidosis and instructed to seek immediate medical attention if they occur.
  • The osmotic tablet formulation (e.g., Fortamet, Glumetza) may result in the tablet shell being passed in the stool; this is normal and does not mean the medication was not absorbed.
  • Long-term metformin use can lead to vitamin B12 deficiency; consider periodic monitoring and supplementation, especially in patients with risk factors or symptoms.
  • Metformin is often the first-line pharmacologic agent for type 2 diabetes due to its efficacy, favorable weight profile (weight-neutral or modest weight loss), and low risk of hypoglycemia when used as monotherapy.
  • Always hold metformin before and for 48 hours after administration of iodinated contrast media or major surgical procedures, and re-evaluate renal function before restarting.
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Alternative Therapies

  • Sulfonylureas (e.g., glipizide, glyburide, glimepiride)
  • DPP-4 inhibitors (e.g., sitagliptin, saxagliptin)
  • SGLT2 inhibitors (e.g., canagliflozin, empagliflozin)
  • GLP-1 receptor agonists (e.g., liraglutide, semaglutide)
  • Thiazolidinediones (e.g., pioglitazone, rosiglitazone)
  • Insulin
  • Alpha-glucosidase inhibitors (e.g., acarbose, miglitol)
  • Meglitinides (e.g., repaglinide, nateglinide)
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Cost & Coverage

Average Cost: Varies widely, typically $10-$50 per 30 tablets (500mg ER)
Generic Available: Yes
Insurance Coverage: Tier 1 (Preferred Generic)
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General Drug Facts

If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more details. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide information about the medication taken, the amount, and the time it happened.