Metformin (Glucophage) for polycystic ovary syndrome

Examples

Generic Name	Brand Name
metformin hydrochloride	Glucophage

How It Works

Metformin lowers blood sugar levels by:

• Decreasing the amount of sugar produced by the liver.
• Increasing the amount of sugar absorbed by muscle cells and decreasing the body's resistance to insulin (insulin resistance).

Lower blood sugar leads to a lesser need for insulin. The body then makes less insulin. Lower insulin leads to lower androgen ("male" hormone) production.

Why It Is Used

Metformin is a diabetes medicine sometimes used for lowering insulin and blood sugar levels in women with polycystic ovary syndrome (PCOS). This helps regulate menstrual cycles, start ovulation, and lower the risk of miscarriage in women with PCOS. Long-term use also lowers diabetes and heart disease risk related to high insulin levels.¹

Metformin:¹

• Does not cause the pancreas to make more insulin. When taken alone, it will not cause low blood sugar (hypoglycemia).
• Lowers the amount of fat (lipids) in the bloodstream and lowers (lipid and triglyceride) levels.
• Reduces abnormal clotting factors and markers of inflammation that can lead to hardening of the arteries (atherosclerosis).
• Decreases the level of androgens.

Metformin can be used to treat women with polycystic ovary syndrome (PCOS) to reduce insulin levels and promote normal ovarian function. Metformin is best used in addition to eating a healthy diet, losing weight, and exercising regularly.

How Well It Works

Metformin lowers insulin, androgen, and cholesterol levels. It also improves metabolism in women who are insulin-resistant.

• Metformin treatment triggers ovulation in about 45% of women with PCOS.²
• Metformin with clomiphene (Clomid) is more likely to start ovulation than either treatment alone.² This combination treatment triggers ovulation in about 75% of women with PCOS.

Metformin may lower the risk of miscarriage and gestational diabetes in women with PCOS.¹But the safety of using metformin throughout pregnancy is not known.

Side Effects

The most common side effects of metformin are:

• Nausea.
• Loss of appetite.
• Diarrhea.
• Increased abdominal gas.
• A metallic taste.

These side effects occur 20% to 30% of the time. Side effects usually decrease over time. The dosage of metformin is usually increased gradually to prevent these possible side effects.³

Blood levels of vitamin B12 can decrease in women who take this medicine, but the lower level usually does not cause health problems.

A rare side effect of metformin use is a condition called lactic acidosis. Lactic acidosis develops when muscles release lactic acid during exercise. If the liver is not able to convert the lactic acid into sugar, the acid builds up in the blood. If not treated, this acid buildup can lead to coma and death. Metformin should not be used in women who:

• Have kidney or liver failure.
• Have low levels of oxygen in their blood (hypoxia).
• Abuse alcohol.
• Are dehydrated.

The use of metformin during pregnancy is not well researched. Be sure to discuss this with your doctor.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

You may need to stop taking metformin temporarily before major surgery or other medical procedures, such as X-rays that use contrast dyes. Talk to your doctor about this beforehand.

The effect of metformin may be increased if you also take cimetidine. Metformin also interacts with anticoagulant medicines, such as warfarin. Discuss your medicine use with your doctor.

Metformin is safe to use in teenage girls with PCOS. Some experts suggest starting long-term metformin therapy when PCOS is first diagnosed, with the goal of lowering the risks of diabetes, infertility, and heart disease. But the safety of long-term treatment is not yet known.⁴

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Author:	Kathe Gallagher, MSW Carrie Henley	Last Updated: May 19, 2006
Medical Review:	Adam Husney, MD - Family Medicine Caroline S. Rhoads, MD - Internal Medicine Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology Samuel S. Thatcher, MD, PhD - Obstetrics and Gynecology, Reproductive Endocrinology
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