Examples

Nifedipine is a tocolytic medication sometimes used during preterm labor to slow uterine contractions. Nifedipine is taken only by mouth (orally) as a tablet or capsule.

Use of nifedipine for the treatment of preterm labor is an unlabeled use of the drug. Nifedipine, a calcium channel blocker, is more commonly used to treat high blood pressure and heart disease.

How It Works

Smooth muscle tissue, like the uterus, needs calcium to contract. Nifedipine blocks the passage of calcium into certain tissues, relaxing the uterine muscles and smooth muscles of blood vessels throughout the body.

Why It Is Used

Nifedipine is used for the treatment of preterm labor when:

• Regular contractions of the uterus have thinned (effaced) the cervix and opened (dilated) it less than 4cm, and the mother's amniotic sac has not broken.
• The mother is healthy.
• The fetus is alive and not in distress.
• Labor needs to be delayed for 24 to 48 hours. This is typically necessary with corticosteroid treatment to help fetal lungs mature. Sometimes labor is delayed so the mother can be moved to a hospital with special facilities for treating premature infants.
• Beta-sympathetic medications (ritodrine and terbutaline) have not stopped uterine contractions.
• The mother is at high risk of suffering the side effects of beta-sympathetic medications (ritodrine and terbutaline) due to such conditions as diabetes, heart disease, or lung disease.¹
• Treatment with other tocolytic medications was stopped because of side effects.

How Well It Works

Small studies so far show that nifedipine may work better than other drugs to slow or stop preterm labor, with fewer problems for newborns.²

Side Effects

Side effects of nifedipine can include:

• Dizziness, lightheadedness, and nervousness.
• Skin flushing or redness.
• Headache.
• Nausea.
• Muscle cramps or tremors.
• Low blood pressure in the mother and a possible decrease in the blood supply to the fetus.

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

What To Think About

• A mother's blood pressure is checked frequently while she takes this medication.
• Pregnant women with liver disease should not take nifedipine.
• Nifedipine should not be used together with magnesium sulfate.

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Citations

1. Dyson DC, et al. (1998). Monitoring women at risk for preterm labor. New England Journal of Medicine, 338(1): 15–19.

2. Haas DM (2005). Preterm birth, search date June 2005. Online version of Clinical Evidence (14): 1–20.