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What to know about hydralazine and heart rate

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Does hydralazine lower heart rate?Other side effectsWhat hydralazine is forMedications for an increased heart rateContacting a doctorSummary
Hydralazine is in a class of medications called vasodilators. Doctors may prescribe it for hypertension or high blood pressure. While it helps lower blood pressure, hydralazine can actually increase heart rate.
Medically reviewed by Monica Kean, PharmD
Updated on October 18, 2023

If you have hypertension, your doctor may suggest taking hydralazine to keep it in check. Before taking the medication, you may wish to discuss the possible side effects with your doctor.

Does hydralazine lower heart rate?

A person is tipping medication out of a bottle.
Photography by Prostooleh/Getty Images

Hydralazine does not typically lower heart rate. Instead, an increased heart rate is a possible side effect.

Tachycardia is the medical term for a heart rate of more than 100 beats per minute in adults. Taking hydralazine can cause tachycardia. If this happens, a doctor may prescribe another medication, such as a beta-blocker, to help lower your heart rate.

Hydralazine works by stimulating the sympathetic nervous system. By stimulating the heart, hydralazine can cause

an increase in heart rate.

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Other side effects of hydralazine

Aside from an increased heart rate, hydralazine can cause other side effects. It’s best to discuss the possible side effects with your doctor before beginning the medication.

Possible side effects of hydralazine include:

  • headaches
  • diarrhea
  • constipation
  • loss of appetite
  • vomiting
  • upset stomach
  • nasal congestion
  • teary eyes
  • rash

In some cases, severe side effects may develop. These can include:

  • muscle pain
  • joint pain
  • chest pain
  • rapid heartbeat
  • fainting
  • swelling in your feet or ankles
  • fever

It is important to seek immediate medical help if you develop serious side effects.

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When might doctors recommend hydralazine?

Doctors recommend hydralazine for hypertension or high blood pressure. They will typically prescribe oral hydralazine for primary hypertension or essential hypertension.

You may require hydralazine intravenously to quickly reduce high blood pressure in an emergency situation.

When combined with isosorbide dinitrate, hydralazine may also be suitable for treating eclampsia along with heart failure with reduced ejection fraction (HFrEF).

What medications can treat an increased heart rate?

Although hydralazine does not lower heart rate, doctors can recommend other medications for an increased heart rate, irregular heart rate, or atrial fibrillation.

Possible medications include:

  • beta-blockers
  • calcium channel blockers
  • digoxin, a cardiac glycoside

If hydralazine is responsible for increased heart rate, your doctor may recommend changing your blood pressure medication or taking medication alongside it to manage your heart rate.

When should you contact a doctor?

You may wish to contact your doctor if you currently take hydralazine and have questions about your current treatment plan. You may wish to discuss any mild side effects you are experiencing.

If you are experiencing any more severe side effects, it is important to seek more immediate medical help. These can include side effects such as chest pain, swelling, and fainting.

You should also seek medical help if you experience symptoms of a rapid heart rate or tachycardia. These can include:

  • shortness of breath
  • fatigue
  • nausea
  • discomfort or pain in the chest
  • a fluttering sensation in the chest
  • palpitations
  • dizziness or lightheadedness
  • syncope or fainting

In severe cases, tachycardia can cause cardiac arrest or unconsciousness.


Hydralazine is a vasodilator medication doctors may prescribe to treat high blood pressure. An increased heart rate is a possible side effect.

If you experience an increased heart rate when taking hydralazine, a doctor may recommend medications to lower your heart rate. Examples include beta-blockers and calcium channel blockers.

It’s best to let your doctor know if you are experiencing any side effects of hydralazine, including an increased heart rate. Symptoms of a rapid heart rate or tachycardia include shortness of breath, pain or discomfort in your chest, dizziness, palpitations, fainting, and more.

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