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Hydralazine

Supportive Care

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What is hydralazine?

Hydralazine (also called Apresoline®) is an antihypertensive (blood pressure lowering medicine). It relaxes the blood vessels and lowers blood pressure. High blood pressure levels can damage kidneys, and may lead to stroke or heart failure. Hydralazine is available as 10 mg, 25 mg, and 50 mg tablets taken by mouth. It is also available as a clear liquid given by vein (IV).

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Possible side effects

  • Low blood pressure (especially with the IV form)
  • Retaining sodium and water
  • Increased heart rate
  • Sudden weight gain
  • Loss of appetite
  • Short of breath
  • Swollen lymph nodes
  • Unusual weak or tired feeling
  • Headache
  • Nausea, vomiting
  • Diarrhea
  • Constipation

Call the doctor right away if you have any of the following side effects:

  • Nasal congestion
  • Low blood counts with an increased risk of bleeding, infection, and fatigue
  • Feeling dizzy and lightheaded or fainting spells
  • Swollen legs or ankles
  • Fast or irregular heartbeat, chest pain, palpitations
  • Skin rash, redness, blisters, or itching
  • Cold, tingling, or numb hands or feet
  • Joint pain, rash, fever, chills, or weakness and fatigue that will not go away (a lupus-like syndrome)

Symptoms of an allergic reaction include: rash, hives, itching, chills, fever, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck.

Not all patients who take hydralazine will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your doctor or pharmacist. 

  • Store the tablets at room temperature in a dry place.
  • Take hydralazine with food. Food increases the amount of drug that gets in your body. If you cannot take this with food every time, then always take it without food. It is important to take this medicine the same way and at the same time each day, so your blood pressure is controlled with the same amount of medicine each day.
  • This medicine may cause you to feel dizzy and lightheaded. Do not operate heavy equipment or drive a motor vehicle until you see how this medicine will affect you. To avoid feeling dizzy or having fainting spells do not sit up or stand up too quickly.
  • You or your nurse should check your blood pressure and heart rate regularly while you are taking hydralazine. Your doctor will tell you what to do if your blood pressure level is low or high. Your dose of hydralazine may change based on your blood pressure level. If your blood pressure is above _____________ or below__________, call your doctor right away. If your heart rate is _____________, call your doctor right away.
  • Hydralazine may affect the way some medicines work. Some medicines may also affect the way hydralazine works. These medicines include:
    • Other blood pressure medicines
    • Medicines for colds and coughs
    • Ibuprofen and other anti-inflammatory medicines
    • Medicines for depression
    • Female hormones (including birth control medicines)
    • Diuretics
    • Alcohol
  • Always tell your doctor if you are taking any of these medicines, or if you start taking any new medicine while you are taking hydralazine.
  • If you have a sudden onset of severe diarrhea or vomiting or if you sweat a lot, tell your doctor right away. This loss of body fluid may decrease your blood pressure.
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Always check the medication label. Many medicines look the same. Do not take any new medicine, including over-the counter medicines or supplements, without checking with your doctor or pharmacist. Talk to your doctor or pharmacist about what to do in the case of a missed dose, allergic reaction, or medical emergency. 

This information is not intended to be a complete guide and is not a substitute for talking with your provider. Medicine names, appearance, formulas, or availability may vary by clinic location. Always follow the instructions given by your care team.

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Reviewed: June 2024