Hydralazine for high blood pressure (Apresoline)

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Hydralazine is used to control high blood pressure.

Treatment with hydralazine is usually long-term.

The most common side-effects are palpitations, swollen feet or ankles, and headache.

Type of medicineVasodilator antihypertensive medicine
Used forThe treatment of high blood pressure
Also calledApresoline®
Available asTablets

Most people with hypertension (high blood pressure) do not feel unwell, but it is important that your high blood pressure is treated even if you feel fine. If left untreated, high blood pressure is a risk factor that can increase your chance of developing heart disease, a stroke, and other serious conditions. Hydralazine will be prescribed alongside other medicines to control high blood pressure.

Hydralazine works by relaxing the muscles in the walls of your blood vessels. This means that your blood vessels widen, which reduces your blood pressure and allows blood and oxygen to circulate more freely around your body. Hydralazine will only be prescribed for you if other treatments are not suitable or effective, as it can increase the amount of water and salt in your body and can increase your heart rate. The other medicines you are prescribed to take alongside it will help to control these side-effects.

Hydralazine is occasionally prescribed by hospital doctors for other heart conditions. If you have been prescribed it for a reason other than high blood pressure, speak with your doctor if you have any questions about your treatment.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking hydralazine it is important that your doctor or pharmacist knows:

  • If you have a condition called systemic lupus erythematosus (this is an inflammatory condition also called lupus or SLE).
  • If you have kidney or liver problems.
  • If you have a problem with your blood vessels, such as coronary artery disease or cerebrovascular disease.
  • if you have a heart condition or have recently had a heart attack.
  • If you are pregnant or breast-feeding.
  • If you have a rare inherited blood disorder called porphyria.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to any medicine.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about hydralazine and a full list of the side-effects which you may experience from taking it.
  • Take hydralazine exactly as your doctor tells you to. It is usual to take one tablet twice daily. Try to take your doses at similar times of day each day, as this will help you to remember to take them. There are two strengths of hydralazine tablet - it is usual to take the 25 mg strength tablet to begin with, but this may then be increased to the higher 50 mg strength. Increasing your dose gradually allows your doctor to make sure that you have the dose that best helps your condition, but also keeps unwanted side-effects to a minimum.
  • Swallow the tablets whole with a drink of water. It is not important whether you take your dose before or after food.
  • If you forget to take a dose, take it as soon as you remember unless your next dose is due. If your next dose is due, then take the dose which is due but leave out the forgotten one. Do not take two doses together to make up for a missed dose.
  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress. You will need to have regular blood pressure measurements and also some blood tests from time to time.
  • Drinking alcohol while you are on hydralazine may increase the chance that you experience side-effects and is not recommended.
  • Your doctor will advise you on what lifestyle changes you can make to help your condition. These may include losing weight if you are overweight, taking regular physical activity, eating a healthy diet, stopping smoking, and reducing the amount of salt in your meals and caffeine in your drinks. It is important that you follow any advice you are given.
  • If you buy any medicines, check with a pharmacist that they are suitable for you to take. This is because some medicines (particularly some anti-inflammatory painkillers) interfere with hydralazine.
  • Treatment with hydralazine is usually long-term unless you experience an adverse effect. Continue to take the tablets unless you are advised otherwise.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking hydralazine. This is because some anaesthetics can affect your blood pressure.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with hydralazine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common hydralazine side-effectsWhat can I do if I experience this?
A fast heartbeat, palpitations, feeling flushed, swollen feet or ankles, chest painsIf any of these symptoms continue or cause you concern, speak with your doctor
HeadacheAsk your pharmacist to recommend a suitable painkiller
Feeling dizzyIf this happens, sit down for a while. Do not drive or use tools or machines until you feel better
Feeling or being sick, diarrhoeaEat simple meals and drink plenty of water to replace lost fluids
Joint or muscle pain, fever, tiredness and generally feeling unwellSpeak with your doctor about this as soon as possible. It may be an early sign of systemic lupus erythematosus-like syndrome

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the sight and reach of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep-out-of date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

  • Manufacturer's PIL, Apresoline® Tablets 25 mg; Amdipharm Mercury Company Limited, The electronic Medicines Compendium. Dated September 2012.
  • British National Formulary; 65th Edition (Mar 2013) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr Helen Huins
Document ID:
615 (v24)
Last Checked:
Next Review:
The Information Standard - certified member

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