Reviewed on 10/25/2021

What Is Hydralazine and How Does It Work?

Hydralazine is a prescription medication used to treat the symptoms of Severe Essential Hypertension, Chronic Hypertension, Hypertensive Crisis, and Congestive Heart Failure.

  • Hydralazine is available under the following different brand names: Apresoline

What Are Dosages of Hydralazine?

Adult and pediatric dosage

Injectable solution

  • 20mg/mL


  • 10mg
  • 25mg
  • 50mg
  • 100mg

Severe Essential Hypertension

  • 10 mg orally every 6 hours for 2-4 days; 25 mg every 6 hours daily for the first week; increase to 50 mg every 6 hours from second week on; adjust dose to lowest effective levels
  • 20-40 mg IM/IV; repeat as necessary
  • Change to oral therapy as soon as possible
  • Pediatric: 1.7-3.5 mg/kg per day IM or IV divided in 4-6 doses

Hypertension (Chronic)

  • Initial: 10 mg orally every 6 hours for 2-4 days; may increase gradually by 10-25 mg/dose every 2-5 days up to 50 mg orally every 6 hours (some patients require 300 mg/day)

Hypertensive Crisis

  • 10-40 mg IV/IM; not to exceed 20 mg/dose; repeat as needed
  • Pregnancy-associated: 5-10 mg IV/IM initially; then 5-10 mg every 20-30 minutes as needed or 0.5-10 mg/hr IV infusion
  • Infants or older: 0.1-0.2 mg/kg IV/IM every 4-6 hours as needed; may increase to usual dose of 1.7-3.5 mg/kg divided every 4-6 hours; not to exceed 20 mg/dose IM or IV or 2 mg/kg every 3-6 hours with cumulative dose not to exceed 9 mg/kg

Congestive Heart Failure

  • Initial dose: 10-25 mg orally every 6-8 hours, titrate dose every 204 weeks
  • Maintenance dose: 225-300 mg/day orally divided every 6-8 hours
  • Infants: 01.-0.5 mg/kg dose IV every 6-8 hours; not to exceed 2 mg/kg
  • Infants and older: 0.75-3 mg/kg per day orally divided every 6-12 hours not to exceed 200 mg/day or 7 mg/kg per day
  • Children and adolescents: 0.15-0.2 mg/kg dose IV every 4-6 hours, not to exceed 20 mg dose

Dosage Considerations – Should be Given as Follows: 

  • See "Dosages."

What Are Side Effects Associated with Using Hydralazine?

Common side effects of Hydralazine include:

  • chest pain, 
  • fast heart rate, 
  • headache, 
  • nausea, 
  • vomiting, 
  • diarrhea, and 
  • loss of appetite

Serious side effects of Hydralazine include:

  • hives, 
  • difficulty breathing, 
  • swelling of the face, lips, tongue, or throat, 
  • chest pain or pressure, 
  • pain spreading to jaw or shoulder
  • fast or pounding heartbeats, 
  • lightheadedness
  • numbness, tingling, or burning pain in hands or feet, 
  • painful or difficult urination
  • little or no urination, 
  • joint pain or swelling with fever, 
  • swollen glands, 
  • muscle aches, 
  • vomiting, 
  • unusual thoughts or behavior, and
  • patchy skin color

Rare side effects of Hydralazine include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Hydralazine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them.  Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

  • Hydralazine has no known severe interactions with other drugs.
  • Hydralazine has serious interactions with the following drugs:
    • iofexidine
    • ionafarnib
    • pexidartinib, and
    • pretomanid
  • Hydralazine has moderate interactions with at least 102 other drugs.
  • Hydralazine has minor interactions with at least 14 other drugs.

This information does not contain all possible interactions or adverse effects.  Visit the RxList Drug Interaction Checker for any drugs interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use.  Keep a list of all your medications with you, and share this information with your doctor and pharmacist.  Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Hydralazine?


Effects of drug abuse

  • None

Short-Term Effects

  • See “What are Side Effects Associated with Using Hydralazine?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Hydralazine?”


  • May induce SLE-type syndrome (usually at >200 mg/day); instruct patients to report joint/chest pain or fever; discontinue therapy unless benefits outweigh risks; steroid therapy may be necessary long-term
  • Use caution in CVA, severe renal impairment, volume depletion, preexisting hypotension, concurrency with other hypotensive agents, CAD (potential contraindication)
  • Use caution in mitral valvular disease; may increase pulmonary artery pressure
  • Discontinue slowly to avoid rapid rise in blood pressure
  • Use with caution in patients with pulmonary hypertension; may cause hypotension
  • Increases fluid and sodium retention; may require treatment or increase in diuretic dose
  • Peripheral neuritis, including numbness, paresthesia, and tingling, reported; treat symptoms with pyridoxine
  • Blood dyscrasias, including reduction in red blood cell count, agranulocytosis, leukopenia, reported with therapy; discontinue therapy if any of the hematologic effects occur

Pregnancy and Lactation

  • Use with caution if benefits outweigh risks.  
  • Excreted in breast milk; use caution

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