Metformin is a medication prescribed by doctors, typically administered in two oral forms: tablets and solutions.
The tablet form of metformin is offered in two varieties: immediate-release and extended-release. The immediate-release variant is commonly found as a generic medication, while the extended-release variant is marketed under the brand names Fortamet and Glumetza.
Both immediate-release and extended-release tablets are also available as generic drugs, typically at a lower cost compared to their branded counterparts. However, it's worth noting that generic versions might not always be available in every strength or form offered by the branded drugs.
Why it’s used
Metformin oral tablets are prescribed to manage elevated blood sugar levels resulting from type 2 diabetes, often in conjunction with dietary adjustments and physical activity.
It is commonly integrated into combination therapy, which necessitates its use alongside other medications for optimal treatment effectiveness.
How it works
Metformin falls under the category of medications known as biguanides, which constitute a group of drugs operating in a similar manner. Typically, they are utilized for treating comparable medical conditions.
Metformin functions by:
- Diminishing the production of glucose (sugar) by the liver.
- Lowering the absorption of glucose by the body.
- Enhancing the effectiveness of insulin within the body.
Insulin is a hormone crucial for facilitating the removal of excess sugar from the bloodstream, thereby reducing blood sugar levels.
Metformin side effects
Metformin oral tablets have the potential to induce both mild and severe side effects. The following outlines some key side effects associated with metformin, although it doesn't encompass all possible reactions.
For further information regarding potential side effects of metformin or advice on managing troublesome reactions, consult your physician or pharmacist.
More common side effects:
Metformin may lead to the following more common side effects:
- Stomach issues such as diarrhea, nausea, stomach pain, heartburn, and gas. These effects may dissipate within a few days to a couple of weeks. Should they persist or worsen, seek guidance from your healthcare provider.
Serious side effects:
Contact your doctor immediately if you experience serious side effects, or dial 911 if symptoms seem life-threatening or if you suspect a medical emergency. Serious side effects may include:
- Lactic acidosis, characterized by symptoms such as tiredness, weakness, unusual muscle pain, difficulty breathing, unusual sleepiness, stomach pains accompanied by nausea or vomiting, dizziness or lightheadedness, and slow or irregular heart rate.
- Hypoglycemia (low blood sugar), which may manifest as headache, weakness, confusion, shaking or feeling jittery, drowsiness, dizziness, irritability, sweating, hunger, or a fast heart rate.
- Low levels of vitamin B12, exhibiting symptoms such as low energy, muscle weakness, loss of appetite, and tingling or numbness in the hands or feet.
Read Also: list of sulfonamide medications
Pros and Cons of metformin
Pros:
- Effective Blood Sugar Control
- Weight Neutral or Weight Loss
- Cardiovascular Benefits
- Low Risk of Hypoglycemia
Cons:
- Gastrointestinal Side Effects
- Lactic Acidosis
- Vitamin B12 Deficiency
- Renal Function Concerns
Differences Between metformin and hydrochlorothiazide
Metformin:
It is primarily used to treat type 2 diabetes mellitus, either alone or in combination with other antidiabetic medications or insulin.
Hydrochlorothiazide:
It is primarily used to treat high blood pressure (hypertension) and edema (fluid retention) associated with conditions such as congestive heart failure, liver cirrhosis, and kidney disorders. It is sometimes used in combination with other antihypertensive medications.
Alternative to metformin
Sulfonylureas:
Drugs like glipizide, glyburide, and glimepiride stimulate the pancreas to release more insulin, helping to lower blood sugar levels. They are often used when metformin alone is not effective in controlling blood sugar.
How to treat low blood sugar
Metformin has the potential to induce low blood sugar reactions, which require prompt treatment.
For mild hypoglycemia (with blood sugar levels between 55–70 mg/dL), the recommended treatment is consuming 15–20 grams of glucose, a type of sugar. You can ingest one of the following options:
- 3–4 glucose tablets
- A tube of glucose gel
- 1/2 cup of juice or regular, nondiet soda
- 1 cup of nonfat or 1 percent cow’s milk
- 1 tablespoon of sugar, honey, or corn syrup
- 8–10 pieces of hard candy, such as lifesavers
After treating the low blood sugar reaction, it's crucial to test your blood sugar levels 15 minutes later. If your blood sugar remains low, repeat the treatment mentioned above. Once your blood sugar returns to the normal range, consume a small snack if your next scheduled meal or snack is more than an hour away.
Failure to address low blood sugar can lead to severe consequences such as seizures, loss of consciousness, and potential brain damage, or even fatality. If you lose consciousness due to low blood sugar or are unable to swallow, someone will need to administer an injection of glucagon to address the low blood sugar reaction. In such cases, seeking immediate medical attention, potentially in an emergency room, may be necessary.
Metformin may interact with other medications
Metformin oral tablets have the potential to interact with various other medications, and these interactions can lead to different effects. Some interactions may hinder the efficacy of a drug, while others might exacerbate side effects.
Here's a list of medications that can interact with metformin, although it's not exhaustive:
- Other antidiabetic medications
- Drugs that affect kidney function, such as certain diuretics (water pills)
- Drugs that impact liver function, like alcohol or certain medications for hepatitis or HIV
- Medications that alter the acidity of the stomach, such as proton pump inhibitors (PPIs)
- Some antibiotics
- Certain heart medications, like beta-blockers or calcium channel blockers
- Corticosteroids
- Estrogens and oral contraceptives
Before starting metformin, ensure you inform your doctor and pharmacist about all the prescription, over-the-counter, and other medications you're taking, as well as any vitamins, herbs, or supplements. Sharing this information can help prevent potential interactions.
If you have any concerns or questions regarding drug interactions that may affect you, don't hesitate to consult your doctor or pharmacist.
Diabetes drugs:
Using certain diabetes medications alongside metformin can lead to low blood sugar levels. In such cases, your doctor might adjust the dosage of your other diabetes medications. Examples include insulin and insulin-releasing medications like glyburide.
Blood pressure drugs:
Diuretics, which lower blood pressure, can potentially increase blood sugar levels and interfere with metformin's effectiveness. Examples are furosemide and hydrochlorothiazide. Nifedipine, a calcium channel blocker for blood pressure, may increase metformin levels in your body, raising the risk of side effects.
Cholesterol drug:
Combining nicotinic acid with metformin might reduce metformin's efficacy in lowering blood sugar.
Glaucoma drugs:
Taking metformin alongside certain glaucoma medications may heighten the risk of lactic acidosis. Examples include acetazolamide, brinzolamide, dorzolamide, and methazolamide.
Topiramate:
Using metformin with topiramate, which treats nerve pain and seizures, may increase the risk of lactic acidosis, making them unsuitable for simultaneous use.
Phenytoin:
Concurrently using phenytoin for seizures with metformin might reduce metformin's effectiveness in lowering blood sugar levels.
Stomach problem drugs:
Combining metformin with cimetidine, used for heartburn and other stomach issues, could raise the risk of lactic acidosis. Alternative medications may be considered instead of cimetidine if you're on metformin.
Phenothiazines:
Taking metformin alongside phenothiazines, antipsychotic medications like chlorpromazine, fluphenazine, and prochlorperazine, could decrease metformin's effectiveness in lowering blood sugar.
Hormone drugs:
Certain hormone medications, such as corticosteroids (inhaled and oral) like budesonide, fluticasone, prednisone, and estrogens including hormonal birth control, conjugated estrogens, and estradiol, may reduce metformin's efficacy in lowering blood sugar levels.
Tuberculosis drug:
Combining isoniazid with metformin might diminish metformin's effectiveness in lowering blood sugar.
Thyroid drugs:
Certain thyroid medications, like desiccated thyroid, levothyroxine, liothyronine, and liotrix, could reduce metformin's effectiveness in lowering blood sugar levels.
Discussing all medications, including over-the-counter drugs and supplements, with your doctor or pharmacist is crucial to avoid potential interactions and ensure your health and safety.
How to take metformin
The dosage of metformin prescribed by your doctor will be determined by several factors, including:
- The type and severity of the condition being treated with metformin.
- Your age.
- The specific form of metformin you are taking.
- Any other medical conditions you may have.
Usually, your doctor will initiate treatment with a low dosage and gradually adjust it over time to achieve the optimal dosage for you. The goal is to find the smallest effective dosage.
Below are the common or recommended dosages for different forms and strengths of metformin. However, it's important to follow the dosage prescribed by your doctor:
Generic: Metformin
- Form: Immediate-release oral tablet
- Strengths: 500 mg, 850 mg, 1,000 mg
- Form: Extended-release oral tablet
- Strengths: 500 mg, 750 mg, 1,000 mg
Brand: Fortamet
- Form: Extended-release oral tablet
- Strengths: 1,000 mg
Brand: Glumetza
- Form: Extended-release oral tablet
- Strengths: 500 mg, 1,000 mg
Your doctor will determine the appropriate dosage based on your individual needs and medical history.
Dosage for type 2 diabetes
Here are the recommended dosages for metformin for different age groups:
Adult dosage (ages 18–79 years):
Immediate-release tablets:
- Typical starting dosage: 500 mg twice per day or 850 mg once per day with meals.
- Dosage changes: Your doctor may increase your dosage by 500 mg weekly or 850 mg every 2 weeks, up to a maximum of 2,550 mg per day in divided doses. If prescribed a dose greater than 2,000 mg per day, you may need to take the medication three times per day.
- Maximum dosage: 2,550 mg per day.
Extended-release tablets:
- Typical starting dosage: 500 mg once per day with the evening meal. For Fortamet, the starting dosage is 500–1,000 mg once per day with the evening meal.
- Dosage changes: Your doctor will increase your dose by 500 mg weekly. If glucose control is not achieved with once-daily dosing, your doctor may switch to twice-daily dosing.
- Maximum dosage: 2,000 mg per day (Fortamet maximum dose is 2,000 mg per day).
Child dosage (ages 10–17 years):
Immediate-release tablets:
- Typical starting dosage: 500 mg twice per day.
- Dosage changes: Your doctor will increase your dosage by 500 mg weekly in divided doses.
- Maximum dosage: 2,000 mg per day.
Extended-release tablets:
- This medication is not studied in children under 18 years of age.
Child dosage (ages 0–9 years):
- This medication is not studied in children under 10 years of age and should not be used.
Senior dosage (ages 80 years and older):
- People aged 80 years and older should not start taking metformin unless they have normal kidney function due to the higher risk of lactic acidosis. If taken at this age, the maximum dose should be avoided.
Conclusion
While metformin is an effective medication for managing type 2 diabetes, it does come with potential side effects. These can range from mild stomach discomfort to more serious issues like lactic acidosis. Common side effects include gastrointestinal symptoms such as diarrhea, nausea, and stomach pain. However, more severe side effects like lactic acidosis, though rare, can be life-threatening and require immediate medical attention.
It's important for patients to be aware of the possible side effects of metformin and to consult with their healthcare provider if they experience any concerning symptoms. Additionally, patients should inform their doctor about any other medications they are taking to avoid potentially harmful interactions. Overall, metformin can be a valuable tool in managing diabetes when used appropriately and under medical supervision.
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The content is intended to augment, not replace, information provided by your clinician. It is not intended nor implied to be a substitute for professional medical advice. Reading this information does not create or replace a doctor-patient relationship or consultation. If required, please contact your doctor or other health care provider to assist you to interpret any of this information, or in applying the information to your individual needs.