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Hydralazine, Oral Tablet

Highlights for hydralazine

  1. Hydralazine oral tablet is only available as a generic drug.
  2. Hydralazine is an oral and injectable drug that’s used to treat high blood pressure. It’s used alone or in combination with other blood pressure-lowering drugs.
  3. Common side effects include headache, loss of appetite, nausea, vomiting, diarrhea, fast heart rate, and chest pain.
  4. Don’t stop taking hydralazine suddenly. Doing so may lead to uncontrolled high blood pressure. It can raise your risk for heart problems, such as chest pain or heart attack. If you need to stop taking this drug, your doctor will slowly lower your dose over two weeks.
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Warnings

Important warnings

  • Lupus Symptoms Warning: Hydralazine may cause symptoms that can feel like lupus. Symptoms can include:
    • joint pain and stiffness
    • a rash on your face
    • fever
    • tiredness
    • loss of appetite
    • nausea
    • weight loss
    • chest pain
    • kidney problems with symptoms such as pink or dark-colored urine, high blood pressure, or swelling in your face, hands, or feet
  • Nerve Damage Warning: Hydralazine may cause the following symptoms of nerve damage:
      numbness or tingling in your hands and feet
    • prickling or itching of your skin
    Tell your doctor if you have these side effects. They may suggest that you take vitamin B6 (pyridoxine) to help decrease these symptoms.
  • Heart Problems Warning: Use this drug with caution if you have heart problems. Hydralazine may cause a heart attack, especially if you already have heart issues. Tell your doctor if you have a heart condition.

About

What is hydralazine?

Hydralazine is a prescription drug. It’s available as an oral tablet and an injection. The injection is only given by a healthcare provider.

Hydralazine is only available as a generic drug. Generic drugs usually cost less than brand-name versions.

Why it's used

Hydralazine is used to treat high blood pressure. It’s used alone or in combination with other blood pressure-lowering medications.

How it works

Hydralazine belongs to a class of drugs called peripheral vasodilators. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions. 

It isn’t fully understood how hydralazine works. It’s thought that the drug acts on the blood vessels directly and relaxes them. This results in lower blood pressure levels.

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Side effects

Hydralazine side effects

Hydralazine oral tablet doesn’t cause drowsiness, but it can cause other side effects.

More common side effects

The more common side effects that can occur with hydralazine include:

  • headache
  • loss of appetite (anorexia)
  • nausea
  • vomiting
  • diarrhea
  • fast heart rate
  • chest pain

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Heart-related symptoms, such as:
    • very low blood pressure (hypotension)
    • fast heart rate
    • dizziness or disorientation
    • swelling in your arms and legs
  • Nerve problems. Symptoms can include:
    • numbness
    • tingling
    • prickling or itching of your skin
  • Depression or anxiety. Symptoms can include:
    • feeling down or not like yourself
    • changes in appetite
    • feeling worried or on edge
    • not being interested in activities you normally enjoy
  • Allergic reaction. Symptoms can include:
    • skin rash
    • itching skin
    • redness to your skin
    • fever
    • chills
    • pain in your joints
  • Trouble breathing
  • Severe constipation
  • Trouble urinating

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Interactions

Hydralazine may interact with other medications

Hydralazine oral tablet can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Examples of medications that can interact with hydralazine are listed below.

Depression medications

Monoamine oxidase inhibitors (MAOIs) can increase the effects of hydralazine. This raises your risk of side effects, such as very low blood pressure (hypotension). These drugs include:

  • isocarboxazid
  • phenelzine sulfate
  • tranylcypromine sulfate
  • selegiline

Diazoxide injection

This drug can cause a severe drop in blood pressure when used with hydralazine.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

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Other warnings

Hydralazine warnings

This drug comes with several warnings.

Allergies

Hydralazine can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it before. Taking it again could be fatal (cause death).

Alcohol interaction

The use of drinks that contain alcohol can increase the blood pressure-lowering side effects from hydralazine. If you drink alcohol, talk to your doctor.

Warnings for certain groups

For people with heart problems: Use this drug with caution if you have heart problems. Hydralazine may cause a heart attack, especially if you already have heart issues. Be sure to tell your doctor about your heart condition before taking hydralazine.

For pregnant women: Hydralazine is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Tell your doctor if you’re pregnant or plan to become pregnant. Hydralazine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

For women who are breastfeeding: Small amounts of hydralazine may pass into breast milk. However, this drug doesn’t typically cause side effects in a child who is breastfed. If you breastfeed your baby, talk to your doctor about the safety of this drug.

For seniors: Older adults may process drugs more slowly. A normal adult dose may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dose or a different schedule.

For children: This drug hasn’t been studied in children younger than 18 years, but it has been used in children.

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Dosage

How to take hydralazine

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Dosage for high blood pressure (hypertension)

Generic

  • Form: oral tablet
  • Strengths: 10 mg, 25 mg, 50 mg, and 100 mg

Adult dosage (ages 18–64 years)

  • Starting dosage: 10 mg taken by mouth 4 times per day for 2–4 days
  • Dosage adjustments: Your doctor may slowly increase your dose up to 50 mg taken 4 times per day.

Child dosage (ages 1–17 years)

  • Starting dosage: 0.75 mg per kg of body weight per day taken by mouth in four divided doses
  • Dosage adjustments: Your doctor may slowly increase your dose over 3–4 weeks.
  • Maximum dosage: 7.5 mg per kg of body weight or 200 mg per day
  • Note: This drug hasn’t been studied in clinical trials for children younger than 18 years, but it has been used in children.

Senior dosage (ages 65 years and older)

There are no specific recommendations for senior dosing. Older adults may process drugs more slowly. A normal adult dose may cause levels of this drug to be higher than normal in your body. If you’re a senior, you may need a lower dose or a different schedule.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.

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Take as directed

Take as directed

Hydralazine is used for long-term treatment. It comes with serious risks if you don't take it as prescribed.

If you don't take it at all

If you don’t take hydralazine as prescribed by your doctor, your blood pressure may stay high (hypertension). This increases your chance of having a stroke and heart attack.

If you stop taking it suddenly

Don’t stop taking hydralazine suddenly. Doing so may lead to uncontrolled high blood pressure. This can put you at a higher risk for heart problems, such as chest pain or a heart attack. If you need to stop taking this drug, your doctor will slowly decrease your dose over two weeks.

If you don’t take it on schedule

Not taking this drug on schedule can put you at a higher risk for heart problems, such as chest pain or heart attack.

What to do if you miss a dose

If you forget to take your dose, take it as soon as you remember. If it’s just a few hours until the time for your next dose, then wait and only take one dose at that time. Never try to catch up by taking two doses at once. This could cause toxic side effects.

If you take too much

You may have severe side effects, such as:

  • very low blood pressure (hypotension)
  • irregular heart rate
  • headache
  • redness and warmth to your skin (flushing)
  • heart attack
  • shock

If you think that you’ve taken too much hydralazine, call your doctor or go to the emergency room right away.

How to tell this drug is working

You may be able to tell if this drug is working if your blood pressure goes down. Your doctor will also monitor your blood pressure to make sure that this medication is working for you.

Important considerations

Important considerations for taking hydralazine

Keep these considerations in mind if your doctor prescribes hydralazine for you.

General

  • Take this drug at the time(s) recommended by your doctor.
  • You can cut or crush the tablet.
  • Hydralazine can be taken with or without food. You should try to stay consistent in how you take this drug. If you usually take it with food, always take it with food and vice versa. This will help reduce your risk of side effects.
  • Taking hydralazine with food can increase the level of the drug in your bloodstream. This may raise your chance for side effects such as an excessive drop in blood pressure or dizziness.

Storage

  • Store hydralazine at room temperature between 68°F and 77°F (20°C and 25°C).
  • Don’t freeze this medication.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry it with you or in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff your pharmacy’s label to clearly identify the medication. Keep the original prescription label with you when traveling.
  • Don’t put this medicine in the car, especially when the temperature is hot or freezing.

Self-management

You may need to check your blood pressure and heart rate at home. You should keep a log with the date, time of day, and your blood pressure readings. Bring this diary with you to your doctor appointments.

You may also need to buy your own blood pressure monitoring machine. These are available for purchase at most pharmacies.

Clinical monitoring

Before starting and during your treatment with hydralazine, your doctor may check your:

  • blood pressure
  • blood tests to check for side effects from the drug
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Alternatives

Are there any alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

Disclaimer:  Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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