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Vasodilators are a type of medicine that can be used to lower high blood pressure.

They work by allowing the blood vessels to relax and widen, allowing the blood to flow through them more easily. They include hydralazine and minoxidil. 


How do direct-acting vasodilators work?

They work by allowing the blood vessels to relax and widen, making it easier for blood to flow through. ‘Vaso’ refers to the blood vessels and ‘dilators’ means that it makes them wider. They act directly on the blood vessels, as opposed to the hormones or nerves which control the blood vessels.


Who can take direct-acting vasodilators?

If you have high blood pressure, your doctor or nurse might suggest you take medicines to lower it. It can take some trial and error to find the right one or the right combination.

Vasodilators are usually used if other drugs are not working well or are not suitable for you. For example, if you have side effects, have other health problems or are taking certain medications. They’re usually used alongside other blood pressure medications. 

Hydralazine may be given to people with heart failure.

They’re not usually given as a first treatment because they can cause your body to hold onto salt and water and can increase your heart rate, but you will be given medicines to control this.


Who won’t be given direct-acting vasodilators?

If you have other health conditions or are taking certain other medications, vasodilators might not be suitable for you, or you will need to be closely monitored. For example, if you:

  • are pregnant, breastfeeding or planning to get pregnant
  • have heart problems such as a fast or irregular heartbeat, valve problems or an enlarged heart
  • have coronary heart disease or angina (chest pain)
  • have had a stroke or heart attack
  • have kidney or liver problems
  • have lupus, also known as SLE

Your doctor will consider your overall health and any treatments you’re having before giving you any new medicines.


Do direct-acting vasodilators have side effects?

All medicines can have side effects, including blood pressure medicines. It’s likely you won’t have any side effects at all with alpha-blockers, or you might have some that are minor and don’t cause you too many problems. The other medicines you’ll be taking with them should help with the side effects.

If you have side effects which don’t improve and are affecting your day-to-day life, you should be able to try a lower dose or a different medicine.

Possible side-effects of direct-acting vasodilators include:

  • headaches
  • a fast or irregular heart beat that you can feel (palpitations)
  • low blood pressure
  • a sudden drop in blood pressure when you go from lying ­or sitting down to standing up (postural hypotension)
  • joint or muscle pain
  • feeling or being sick, or having diarrhoea
  • chest pain
  • feeling flushed, fever, or skin rashes
  • feeling dizzy
  • blocked nose
  • swollen feet or ankles or weight gain, caused by fluid retention
  • fine body hair becoming darker and thicker (with minoxidil)

The leaflet that comes with the medication will have a full list of side effects.


Taking direct-acting vasodilators

They’re normally taken as one tablet, twice a day.

Check with your doctor or pharmacist before taking any other medicines at the same time as direct acting vasodilators, as they can interact, including medicines you buy over the counter such as painkillers and anti-inflammatories.  

If you start taking high blood pressure medicines, it’s likely you will need to keep taking them for the long term. If your blood pressure stays under control for several years, you might be able to take a lower dose or stop taking them altogether.

It’s important that you don’t simply stop taking them because your blood pressure will quickly rise again. Always let your doctor, nurse or pharmacist know if you’re struggling because there could be other options you can try.


Read more

Non-standard medicines for high blood pressure information sheet 

   Download our Non-standard medicines information sheet [PDF 23,510KB].



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