By Medically reviewed by hellodoktor

Generic Name: Hydralazine Brand Name(s): Generics only. No brands available.


What is hydralazine used for?

Hydralazine is used with or without other medications to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Hydralazine is called a vasodilator. It works by relaxing blood vessels so blood can flow through the body more easily.

Hydralazine may also be used with other medications to treat heart failure.

How should I take hydralazine?

Hydralazine is usually given as an injection at your doctor’s office, hospital, or clinic. If you will be using hydralazine injection at home, a health care provider will teach you how to use it. Be sure you understand how to use hydralazine injection. Follow the procedures you are taught when you use a dose. Contact your health care provider if you have any questions.

Do not use hydralazine injection if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.

Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.

How do I store hydralazine?

Hydralazine is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store hydralazine in the bathroom or the freezer. There may be different brands of hydralazine that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush hydralazine down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using hydralazine?

Before using this drug, tell your doctor if:

  • You are pregnant or breastfeeding. This is because, while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
  • You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • You have allergy with any of active or inactive ingredients of hydralazine or other medications.
  • You have any other illnesses, disorders, or medical conditions.
  • You have blood problems (e.g., porphyria), blood vessel problems, heart problems, low blood pressure, low levels of vitamin B6 in your blood, kidney problems, or lupus.
  • You have a history of stroke.
  • You have or have ever had coronary artery disease, rheumatic heart disease, kidney or liver disease, or a heart attack.
  • You are having surgery, including dental surgery, tell the doctor or dentist that you are taking hydralazine.

Ask your doctor about the safe use of alcohol while you are taking hydralazine. Alcohol can make the side effects from hydralazine worse.

Is it safe during pregnancy or breastfeeding?

There isn’t enough information about the safety of using hydralazine during pregnancy and breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking hydralazine.

Side effects

What side effects can occur from hydralazine?

Check with your doctor if any of these most common side effects persist or become bothersome:

Seek medical attention right away if any of these severe side effects occur:

  • Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue)
  • Chest pain
  • Decreased or difficult urination
  • Depression
  • Fainting
  • Fast or irregular heartbeat
  • Fever, chills, or sore throat
  • Joint pain
  • Mental or mood changes
  • Numbness of an arm or leg
  • Numbness or tingling of the skin
  • Persistent fatigue or weakness
  • Severe or persistent headache or dizziness
  • Unusual bruising or bleeding
  • Vision changes
  • Yellowing of the eyes or skin

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with hydralazine?

Hydralazine may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products that may interact with this drug are:

  • Medicines that may affect your blood vessels, medicines that treat high blood pressure (e.g., diazoxide), or other vasodilators (e.g., isosorbide, nitroglycerin) because they may increase the risk of hydralazine’s side effects. Check with your doctor or pharmacist if you have questions about which medicines may affect your blood vessels.
  • Monoamine oxidase (MAO) inhibitors (e.g., phenelzine) because the risk of serious side effects may be increased.
  • Beta-blockers (e.g., propranolol) because the risk of their side effects may be increased by hydralazine injection.
  • Epinephrine because its effectiveness may be decreased by hydralazine injection.

Does food or alcohol interact with hydralazine?

Hydralazine may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with hydralazine?

Hydralazine may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using hydralazine.

What is the dose of hydralazine for an adult?

Usual Adult Dose for Hypertension

Initial dose: 10 mg orally 4 times a day for the first 2 to 4 days. Increase to 25 mg orally 4 times a day for the balance of the first week.

For the second and subsequent weeks, increase dosage to 50 mg orally 4 times a day.

Maintenance dose: Adjust dosage to the lowest effective levels.

Usual Adult Dose for Hypertensive Emergency

Usual dose: 20 to 40 mg IV or IM, repeated as necessary. Certain patients (especially those with marked renal damage) may require a lower dose.

Usual Adult Dose for Congestive Heart Failure

Initial dose: 10 mg orally 4 times a day.

Maintenance dose: Doses up to 800 mg three times daily have been effective in reducing afterload in the treatment of congestive heart failure.

What is the dose of hydralazine for a child?

Safety and effectiveness in pediatric patients have not been established in controlled clinical trial, although there is experience with the use of Hydralazine hydrochloride in pediatric patients. The usual recommended parenteral dosage, administered intramuscularly or intravenously, is 1.7-3.5 mg/kg of body weight daily, divided into four to six doses.

How is hydralazine available?

Hydralazine is available in the following dosage forms and strengths:

  • Solution, Injection, as hydrochloride: 20 mg/mL (1mL)
  • Tablet, Oral, as hydrochloride: 10 mg, 25 mg, 50 mg, 100 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of hydralazine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: July 26, 2017 | Last Modified: September 12, 2019

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