Hydralazine for High Blood Pressure During Pregnancy

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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 whether or not a woman has 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

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Call 911 or other emergency services right away if you have:

  • Trouble breathing.
  • Swelling of your face, lips, tongue, or throat.

Call your doctor if you have:

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

Common side effects of this medicine include:

  • Diarrhea.
  • Fast heart rate (tachycardia).
  • Headache.
  • Nausea or vomiting.
  • Lack of appetite.

The rapid lowering of blood pressure with this medicine may affect blood flow to the fetus. So it is done under close medical supervision.

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.

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Advice for women

When you are pregnant or breast-feeding, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant or breast-feeding.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

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



  1. Cunningham FG, et al. (2010). Pregnancy hypertension. In Williams Obstetrics, 23nd ed., pp. 706–755. New York: McGraw-Hill.
  2. Roberts JM, Funai EF (2009). Pregnancy-related hypertension. In RK Creasy, R Resnik, eds., Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 6th ed., pp. 651–688. Philadelphia: Saunders.


ByHealthwise Staff
Primary Medical ReviewerSarah Marshall, MD - Family Medicine
Specialist Medical ReviewerWilliam Gilbert, MD - Maternal and Fetal Medicine
Last RevisedNovember 5, 2012

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