Hydralazine for high blood pressure during pregnancy


Generic Name

Hydralazine is sometimes used to treat high blood pressure during pregnancy. It can be given through a vein (intravenously, or IV) to quickly lower severe high blood pressure or by mouth as a tablet to control high blood pressure over a period of time.

How It Works

Hydralazine relaxes the smooth muscle of blood vessels. This relaxation causes the blood vessels to widen (dilate), reducing blood pressure.

Why It Is Used

Hydralazine is used to lower severe high blood pressure during pregnancy, with or without preeclampsia.

Hydralazine should not be used by women who have kidney disease or who are allergic to this medicine.

How Well It Works

Hydralazine provides dependable and effective reduction of severely high blood pressure in pregnant women.1, 2

Side Effects

The side effects of hydralazine can usually be reversed by lowering the dosage. Hydralazine side effects include:

  • Nausea or vomiting and lack of appetite.
  • Diarrhea.
  • Dizziness.
  • Fast heart rate (tachycardia).
  • Flushing.
  • Weight loss.

Rapid lowering of blood pressure with this medicine may affect blood flow to the fetus. It is therefore done under close medical supervision.

Rare side effects include:

  • Headache and dizziness.
  • Severe pain in the chest (angina).
  • Skin rash.
  • Fever.
  • Shortness of breath.

If you are being treated with hydralazine, you should report any of these less common side effects to your doctor.

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

What To Think About

Hydralazine lowers blood pressure quickly. For this reason, both mother and fetus are closely monitored during its use. Blood pressure is checked as often as every 15 minutes while the woman is being given intravenous hydralazine.

Hydralazine should not be used by women who have kidney disease or who are allergic to this medicine.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.



  1. Cunningham FG, et al. (2005). Hypertensive disorders in pregnancy. In Williams Obstetrics, 22nd ed., pp. 761–808. New York: McGraw-Hill.
  2. Roberts JM (2004). Pregnancy-related hypertension. In RK Creasy, R Resnik, eds., Maternal-Fetal Medicine, 5th ed., pp. 859–899. Philadelphia: Saunders.

Last Updated: November 14, 2008

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