METFORMIN

Generic Name

metformin (met FORE min)

Brand Names

Glucophage, Glucophage XR, Riomet

What is the most important information I should know about Metformin?

A small number of people who have taken metformin have developed a serious condition called lactic acidosis that has been fatal in up to 50% of cases. Lactic acidosis has occurred most often in people whose kidneys were not working properly. Liver problems may also increase the risk of developing lactic acidosis. Stop taking metformin and call your doctor immediately if you experience a feeling of general discomfort or sickness; weakness; sore or aching muscles; trouble breathing, unusual drowsiness, dizziness or lightheadedness; unusual or unexplained stomach upset (after the initial stomach upset that may occur at the start of therapy with metformin); or the sudden development of a slow or irregular heartbeat. These may be signs of lactic acidosis.

Avoid excessive alcohol intake while taking metformin. Together, alcohol and metformin may increase the risk of lactic acidosis and hypoglycemia.

Metformin does not usually cause hypoglycemia (low blood sugar). Nevertheless, hypoglycemia may occur in the treatment of diabetes, as a result of skipped meals, excessive exercise, or alcohol consumption. Know the signs and symptoms of low blood sugar, which include hunger, headache, drowsiness, weakness, dizziness, a fast heartbeat, sweating, tremor, and nausea. Carry candy or glucose tablets to treat episodes of low blood sugar.

What is Metformin?

Metformin is used to regulate blood glucose (sugar) levels. Metformin works in three ways: first, it reduces the amount of glucose produced by your liver; second, it reduces the amount of glucose absorbed from food through your stomach; and third, it makes the insulin that your body produces work better to reduce the amount of glucose already in your blood.

Metformin is used to treat non-insulin-dependent diabetes mellitus (NIDDM or Type II diabetes). Metformin may be used alone or together with insulin or other diabetes medicines.

Metformin may also be used for purposes other than those listed in this medication guide.

What should I discuss with my healthcare provider before taking Metformin?

Do not take metformin without first talking to your doctor if you

• have kidney disease
• have liver disease
• have congestive heart failure
• have acute or chronic metabolic acidosis, including diabetic ketoacidosis
• have had a heart attack or a stroke
• have a serious infection, illness, or injury
• need to have surgery
• need to have x-rays or other procedures using injectable contrast agents
• are dehydrated (have lost water from your body) due to diarrhea, vomiting, fever, heat stroke, decreased fluid intake, or any other cause
• drink alcohol
• are 80 years of age or older and have not had your kidney function tested

You may not be able to take metformin, or you may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.

Metformin is in the FDA pregnancy category B. This means that it is unlikely to harm an unborn baby. Usually, your doctor will want to prescribe insulin to control diabetes during pregnancy. Do not take metformin without first talking to your doctor if you are pregnant.

Metformin passes into breast milk and may affect a nursing baby. Do not take metformin without first talking to your doctor if you are breast-feeding a baby.

If you are over the age of 65 years, there may be an slight increase in the risk of developing lactic acidosis due to a natural decline in kidney function with advancing age. A lower dose or special monitoring may be necessary during your treatment.

How should I take Metformin?

Take metformin exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain the instructions to you.

Take the tablets with a full glass of water.

Do not crush, chew, or break the Glucophage XR tablets. Swallow them whole. They are specially formulated to release the medication slowly in the body.

To ensure that you get a correct dose, measure the metformin solution with a dose-measuring spoon, dropper, or cup, not a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist where you can get one.

Take metformin with a meal to reduce nausea, diarrhea, and upset stomach that may occur with metformin therapy. These symptoms may be more likely to occur during the first few weeks of therapy.

Occasionally, inactive ingredients in the metformin extended-release (Glucophage XR) tablets may pass through your body undissolved and appear in the stool as a soft mass. This is not harmful, and the medication has been absorbed by your body.

It is important to take metformin regularly to get the most benefit.

A decrease in vitamin B12 may also occur during metformin therapy. Your doctor may want to monitor your blood levels of vitamin B12 and you may need to take B12 supplements. A vitamin B12 deficiency may rarely cause anemia.

Your healthcare provider may recommend regular monitoring of blood sugar levels with blood or urine tests.

Your doctor may want you to have blood tests or other medical evaluations during treatment with metformin to monitor progress and side effects.

Store metformin tablets and oral solution at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and only take the next regularly scheduled dose. Do not take a double dose.

What happens if I overdose?

Seek emergency medical attention if an overdose is suspected.

An overdose of metformin is likely to cause lactic acidosis. Symptoms of lactic acidosis include a feeling of general discomfort or sickness; weakness; sore or aching muscles; trouble breathing; unusual drowsiness, dizziness or lightheadedness; unusual or unexplained stomach upset (after the initial stomach upset that may occur at the start of therapy with metformin); and the sudden development of a slow or irregular heartbeat.

What should I avoid while taking Metformin?

Avoid excessive alcohol intake while taking metformin. Together, alcohol and metformin may increase the risk of lactic acidosis and hypoglycemia.

Follow diet, medication, and exercise routines closely. Changing any of these things can affect blood sugar levels.

Tell your doctor or other health care provider that you are taking this medication if you need to have surgery or x-ray procedures that require injection of contrast agents. Treatment with metformin may need to be stopped for a short period of time.

Tell your doctor that you are taking metformin if you become ill, if you have a heart attack; if you have a stroke; if you develop congestive heart failure; if you experience diarrhea, vomiting, fever, or dehydration from any cause; or if you decrease the amount of food or liquid in your normal diet. You may need to stop your treatment with metformin for a short amount of time until you are feeling better.

What are the possible side effects of Metformin?

Stop taking metformin and seek emergency medical attention if you experience an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives).

A small number of people who have taken metformin have developed a serious condition called lactic acidosis that has been fatal in up to 50% of cases. Lactic acidosis has occurred most often in people whose kidneys were not working properly. Liver problems may also increase the risk of developing lactic acidosis. Stop taking metformin and call your doctor immediately if you experience a feeling of general discomfort or sickness; weakness; sore or aching muscles; trouble breathing, unusual drowsiness, dizziness or lightheadedness; unusual or unexplained stomach upset (after the initial stomach upset that may occur at the start of therapy with metformin); or the sudden development of a slow or irregular heartbeat. These may be signs of lactic acidosis.

Metformin does not usually cause hypoglycemia (low blood sugar). Nevertheless, hypoglycemia may occur in the treatment of diabetes, as a result of skipped meals, excessive exercise, or alcohol consumption. Know the signs and symptoms of low blood sugar, which include hunger, headache, drowsiness, weakness, dizziness, a fast heartbeat, sweating, tremor, and nausea. Carry candy or glucose tablets to treat episodes of low blood sugar.

Other, less serious side effects may be more likely to occur. Continue to take metformin and talk to your doctor if you experience

• nausea, vomiting, abdominal pain, or diarrhea at the start of therapy
• abdominal bloating or increased gas production
• decreased appetite or changes in taste (metallic taste in your mouth)

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

What other drugs will affect Metformin?

Before taking this medication, tell your doctor if you are taking any of the following medications

• a diuretic (water pill) such as furosemide (Lasix), bumetanide (Bumex), ethacrynic acid (Edecrin), torsemide (Demadex), amiloride (Midamor), triamterene (Dyazide, Maxzide, Dyrenium), spironolactone (Aldactone), hydrochlorothiazide (HydroDiuril), chlorothiazide (Diuril), chlorthalidone (Hygroton), indapamide (Lozol), metolazone (Zaroxolyn, Mykrox), and others
• a phenothiazine such as chlorpromazine (Thorazine), prochlorperazine (Compazine), promethazine (Phenergan), and others
• an estrogen (Premarin, Prempro, Ogen, and others) or birth control pill (Ovral, Lo-Ovral, Ortho-Novum, Triphasil, Levlen, Tri-Levlen, Alesse, and others)
• a calcium channel blocker such as nifedipine (Adalat, Procardia), verapamil (Calan, Verelan, Isoptin), diltiazem (Cardizem, Dilacor XR), felodipine (Plendil), bepridil (Vascor), amlodipine (Norvasc), and others
• a steroid medication such as prednisone (Deltasone), methylprednisolone (Medrol), dexamethasone (Decadron), and others
• a thyroid medication (Synthroid, Levoxyl, Levothroid, and others)
• digoxin (Lanoxin, Lanoxicaps)
• procainamide (Pronestyl)
• quinidine (Cardioquin, others)
• cimetidine (Tagamet, Tagamet HB) or ranitidine (Zantac, Zantac 75)
• morphine (Astramorph, MS Contin, Roxanol, and others)
• trimethoprim (Proloprim, Trimpex, Septra, Bactrim)
• phenytoin (Dilantin)
• isoniazid (Nydrazid)
• nicotinic acid or niacin (Nicobid, Nicolar, others)

You may not be able to take metformin, or you may require a dosage adjustment or special monitoring if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with metformin or affect your condition. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including vitamins, minerals, and herbal products.

Where can I get more information?

Your pharmacist has more information about metformin written for health professionals that you may read.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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