Metformin and the extended-release version, metformin ER, are generic drugs sold under brands such as Glucophage and Fortamet. Metformin is prescribed to treat type 2 diabetes in people age 10 and over. The drug increases the body's sensitivity to insulin and decreases the amount of sugar the liver produces. Many side effects are possible with metformin use.
Metformin is available in tablets in a variety of doses. For both youths and adults, starting dose is usually 500mg twice a day of the regular version or once a day of the ER version, and adults also have the option of starting with the ER version at 750mg once a day. The dose is gradually increased if necessary. Some people have fewer side effects with the extended-release version.
Common Side Effects
The most common side effects associated with metformin are loss of appetite, metallic taste, nausea, vomiting, heartburn, indigestion, intestinal gas, bloating and diarrhea. About one of every three patients experience these symptoms, and about one of 20 discontinue using metformin for these reasons, according to the MedicineNet website. These side effects can be decreased or eliminated by reducing the dose, or by using metformin ER instead of the regular version. Most people adjust to the medication quickly and the side effects disappear. Elderly people tend to be more sensitive to the effects of metformin.
Gastrointestinal symptoms that begin after several days or weeks or that occur initially, then disappear and reappear later, can be signs of a serious disorder called lactic acidosis. About one in every 30,000 metformin users develops lactic acidosis, which can be fatal. Symptoms are abnormal heartbeat, chills, difficulty breathing, drowsiness, fatigue, indigestion, light-headedness, muscle pain, and weakness.
Some people are more at risk for lactic acidosis, including people with reduced liver or kidney function, congestive heart failure, poor circulation and other serious illnesses. People who are dehydrated or who drink a great deal of alcohol also are more susceptible. Elderly people, especially those over 80, are more at risk for metformin-induced lactic acidosis as well.
Metformin ER 500 and other dosages of the medication can cause low blood sugar. People with type 2 diabetes usually are already familiar with the symptoms of hypoglycemia, which include chills, dizziness, drowsiness, headache, light-headedness, intense hunger or loss of appetite, perspiration, rapid heartbeat, shaking or tremors, and weakness. Consuming sweet carbohydrates such as fruit, fruit juice, or candy can alleviate this problem. People who experience hypoglycemia should stop taking metformin and consult with their physician.
Interactions with several drugs and herbs are possible with metformin ER 500 and other dosages. These include blood pressure medications, cimetidine, clomiphene, corticosteroids, decongestants, diuretics, fenugreek, ginseng, insulin and other diabetes medication, oral contraceptives and estrogens, and others. Additionally, people planning to have an X-ray or other scanning procedure requiring an iodine-based contrast agent should stop taking metformin ahead of time, because the contrast agent can react with metformin. The physician will advise how soon to discontinue metformin use.