Hydralazine (Oral)

Hydralazine is an oral medication that is used to treat high blood pressure. It is also used to treat certain complications caused by hypertension in pregnant women.


In the US, hydralazine is sold under the product name, Apresoline. The drug comes in tablet form and is available only with a doctor's prescription.

Hydralazine is used to treat patients who are suffering from hypertension. The medicine is also used to mitigate high blood pressure in pregnant women, a complication that can cause eclampsia or pre-eclampsia. Hydralazine is also used in trauma cases where the patient's blood pressure has become extremely high, resulting in a hypertensive crisis.

High blood pressure is a serious condition that places extra workload on the arteries and on the heart. If the condition is allowed to persist untreated for any length of time, damage can be caused to the blood vessels that supply the kidneys, brain, and heart. This damage can cause heart failure, stroke, or kidney failure.

Hydralazine is one of a class of medications called vasodilators. It works by causing the blood vessels to relax, thus increasing the volume of blood that makes its way to the heart, improving oxygen supply and reducing the heart's workload.

This medicine cannot cure your high blood pressure, but it will help to control it.

Conditions treated

  • Hypertension

Type of medicine

  • Vasodilator
  • Tablet
  • Syrup

Side effects

In addition to the effects it is designed to have, hydralazine can cause a few unwanted effects. You may not experience any of these effects, but if you do, you may need to speak to your treating physician, as further medical attention may be necessary to control them.

If you notice any of the effects listed below, check with your GP:

  • Yellow eyes and skin
  • Weakness in feet or hands
  • Stomach or upper right abdominal pain
  • Unusual feelings of tiredness or weakness
  • Unusual bleeding or bruising
  • Sores, ulcers, or white spots in the mouth
  • Trembling or shaking of the feet or hands
  • Tightness of the chest
  • Painful, swollen, or tender lymph glands in the groin, neck, or armpit
  • Swelling of the lower legs or feet
  • Sweating
  • Itching or skin rash
  • Shortness of breath
  • Shakiness in the arms, legs, feet, or hands
  • Pale skin
  • Painful or difficult urination
  • Tingling, numbness, pain, or weakness in the feet
  • Nausea
  • Muscle pain
  • Lower back or side pain
  • Lightly colored stools
  • Joint pains
  • A general feeling of being unwell or weak
  • Sore throat and fever
  • Rapid, pounding, or irregular pulse or heartbeat
  • Feelings of dizziness, faintness, or lightheadedness when rising suddenly from a prone or seated position
  • Difficult or labored breathing
  • Dark urine
  • Cough
  • Confusion
  • Clumsiness or unsteadiness
  • Chills
  • Chest tightness or heaviness
  • Chest pain or discomfort
  • Sensations of burning, itching, crawling, numbness, tingling, prickling, or "pins and needles"
  • Burning of the mouth or face
  • Blurred vision
  • Blisters on the skin
  • Blindness or vision changes
  • Black, tarry stools
  • Back, arm, or jaw pain

The symptoms listed below could mean that you have taken an overdose of hydralazine. If you experience any of these symptoms, you must contact your emergency doctor immediately:

  • Reddening of the neck, face, and arms
  • Headache
  • Feelings of warmth

There are a number of side effects that have been reported by some people who have been treated with hydralazine that do not generally require further medical attention. These effects usually vanish on their own as your body gets used to the new drug. Your GP may also be able to recommend ways in which you can manage or reduce these effects.

If you find that any of the following effects are very persistent or troublesome, ask your GP for advice:

  • Weight loss
  • Watery eyes
  • Stuffy nose
  • Rash, hives, welts, or itching
  • Pain in the joints
  • Muscle pain, stiffness, or cramp
  • Loss of appetite
  • Feeling anxious or depressed
  • Dizziness
  • Difficulty with moving
  • Diarrhea
  • Constipation

There may be other side effects experienced by patients that are not reported in this guide. If you notice anything else untoward, check with your GP.


You must take this medication exactly as you have been instructed to by your GP. Do not take less or more of the medicine than you have been prescribed, or take it more frequently. Your dose may need regular adjustment to establish the most suitable level for your condition.

Your hypertension therapy may also include making changes to your diet, especially reducing your salt intake. Before you decide to change your diet, check with your GP for advice and further guidance.

Many patients who suffer from hypertension do not realize that they have this health condition. You may feel perfectly normal while you are taking hydralazine, but you should not stop taking it unless your doctor tells you to. In addition, be sure to keep any appointments with your GP, even if you feel fine.

You should be aware that hydralazine will not provide a cure for your hypertension, but it can help to control it. You should continue taking this medicine as you have been told to in order to keep your blood pressure under control. If you do not treat your high blood pressure, you could develop serious health conditions including kidney disease, stroke, heart failure, and blood vessel disease.

For best results, take this drug when your stomach is empty, an hour or two before a meal or a couple of hours afterwards.

If you are taking the oral solution form of this drug, you may prefer to take it mixed with apple sauce or fruit juice. Take the medication straight after mixing and be sure to take the whole dose.

Dosage rates

The dose of hydralazine that you are prescribed will vary between different people. Keep to the instructions on the dispensary label or follow your GP's directions. The information shown in this guide is based on the recommended average dose for hydralazine. If your dose is not the same as this, you must not alter it unless your GP instructs you to do so.

The dose of hydralazine that you take, the duration of your course, and the number of daily doses you are required to use will be dependent on the health condition for which you are using the drug.

For hypertension (oral solution):

  • Adults: 40 mg to 200 mg daily, split across two or four doses.
  • Children: The dose and use of the drug will be decided by your GP and is based on body weight. Usually, the dose is 0.75 mg to 7.5 mg per kg of body weight daily, split into two or four doses.

For hypertension (tablets):

  • Adults: Initially, 10 mg four times daily. Your dose may be adjusted by your GP as required, but it does not usually exceed more than 50 mg four times daily.
  • Children: The dose and use of the drug will be decided by your GP and is based on bodyweight. Usually, the starting dose is 0.75 mg per kg of bodyweight daily, split into four doses. Your child's dose may be adjusted by your GP as required, but it does not usually exceed more than 7.5 mg per kg of bodyweight or 200 mg daily.

In order to get the most benefit from using hydralazine it is important to use it regularly and at the same times each day. It may take a few weeks before you begin to feel the full benefit of hydralazine. You must not stop taking hydralazine abruptly, as this could make your condition worse. Your doctor will tell you how to gradually decrease the dose of this drug if necessary.

If you forget to take one of your doses of hydralazine, take it immediately if you can. Note that if your next dose is due, you should skip it and revert to your usual dosing regimen. You should not take twice the dose you have been prescribed as this could cause side effects.


Drug interactions

There are some medicines that should not be used together, as doing so could cause an interaction. In some cases, it may be appropriate to use two drugs at the same time, depending on your condition, even though interactions could take place. Under these circumstances, your GP may elect to change the dose or frequency of one or both of your medications. Be sure to tell your GP if you are using any other prescription or over the counter drugs.

Other interactions

Some drugs should not be used when you are eating particular food groups as this could cause an interaction. In addition, some drugs preclude the use of alcohol or tobacco, as this could also cause interactions.

Using hydralazine with enteral nutrition or when eating could cause some side effects, although it may be unavoidable sometimes. If you do need to use this drug with food, your doctor may advise you to change the dose or frequency of use, or provide you with specific guidance about the use of food, tobacco, or alcohol.

Medical interactions

Some historical or existing medical problems can affect how hydralazine works. You must tell your GP if you have any other health issues, especially any of the following mentioned below.

If you have any of the following conditions, you should use hydralazine with extreme caution, as this medicine can make all these conditions worse:

  • Systemic lupus erythematosus
  • Stroke
  • Peripheral neuritis (nerve problem)
  • Hypotension (low blood pressure)
  • Heart rhythm problems
  • History of heart attack
  • Blood disease
  • Angina (severe chest pain)

Patients should be aware that hydralazine must not be used in people who have ever suffered from coronary heart disease or mitral valvular rheumatic heart disease.

Hydralazine must be used with caution by patients who have a history of kidney disease, as the effects of the drug could be increased due to its slower removal from the body.

If you suffer from phenylketonuria, you should note that the oral solution version of hydralazine contains aspartame, which can cause this condition to become worse.


When you decide to use any form of medication, you should have a discussion with your GP about the benefits of doing so and also the risks. When deciding whether to commence treatment with hydralazine, you should bear in mind the following considerations:


If you have ever noted any allergic or other bad reactions to hydralazine or to any other form of medications, you must tell your GP. In addition, you should tell your GP if you have any known allergies to certain food groups, food colors, preservatives, or animal derivatives.


There have been no specific studies into the effect of hydralazine in pediatric patients. However, it is thought that the drug is safe to use in children. If you have any concerns in this regard, you should discuss the use of this drug with your GP.


It is thought that the use of hydralazine in geriatric patients is safe. However, elderly patients are more likely to have kidney problems, and the dose may therefore need to be adjusted accordingly.

Pregnancy and breastfeeding

There is no evidence to indicate that using hydralazine in pregnant women could cause harm to the unborn baby. However, if you are expecting a baby, you may wish to discuss any concerns that you have with your doctor before you begin taking hydralazine.

Similarly, studies have indicated only a minimal risk to a nursing infant when the mother is taking hydralazine. You may wish to discuss this further with your midwife or GP, and perhaps consider using an alternative feeding solution for your child while you are receiving treatment with this medicine.

Medical considerations

You must attend your GP regularly for checks to make sure that your body is reacting to hydralazine as desired and to discuss any side effects that you have noticed. It may be necessary for you to have blood tests as part of this process.

This medicine can make some people feel dizzy and it can sometimes cause headaches. If you are affected in this way, do not drive, operate machinery or participate in any other activities that could be dangerous.

You must not use any other medicines while you are taking hydralazine unless your doctor has cleared their use first. This includes over the counter medications for coughs, colds, hay fever, diet control, or sinus problems, as these could increase your blood pressure.


Keep this medication in a closed container and at room temperature, away from direct sunlight, heat sources, and damp. Do not freeze the medicine.

Keep hydralazine well away from children and pets. If a pet does consume any of your medicine, contact your vet as soon as possible.

Do not keep any medicine that you no longer need or that has become out-of-date.


Hydralazine is a vasodilator that is used to treat patients who have high blood pressure. The drug is also used to control high blood pressure during pregnancy, a complication that sometimes causes serious conditions called eclampsia or pre-eclampsia. Hydralazine is also used in trauma cases where a hypertensive crisis occurs.

Hydralazine cannot cure your high blood pressure, but it is very effective in helping to control it.