There are many different types of blood pressure medicine. Some are used very often because they are effective and cause relatively few side-effects. Then there are others that are not used so commonly.

These “non-standard” blood pressure medicines would only usually be used in special circumstances – for example if you are pregnant or breastfeeding, if you are having difficult side-effects from other medicines, or if your blood pressure is not being controlled enough with other medicines.

Alpha-blockers

Alpha-blockers block the effects of a hormone called adrenaline. When adrenaline enters your blood stream it causes your blood vessels to ­narrow. This gives your blood less space to move through, which will raise your blood pressure.

Alpha-blockers lower your blood pressure by ­stopping adrenaline from having its full effect. This allows your blood vessels to relax and widen, making it easier for blood to flow through.

Who might be given alpha-blockers?

You would rarely be given an alpha-blocker would as a first choice of medicine for high blood ­pressure. They would normally be used as a third or fourth choice. Alpha-blockers may also be given to men with an enlarged prostate or to people ­who have a phaeochromocytoma (rare tumour of the adrenal gland which raises blood pressure).

Who would not be given alpha-blockers?

If you are pregnant, breastfeeding or planning a pregnancy, you should not be given an alpha-blocker.

Alpha-blockers are not normally given to women as they can cause stress incontinence and loss of bladder control. You will not be given an alpha-blocker if you have a history of postural ­hypotension (a sudden drop in blood pressure when sitting up or standing up) or if you have ever fainted after passing urine.

You may not be given an alpha-blocker if you have a history of heart failure, decreased liver or kidney function, or have Parkinson’s disease.

Alpha-blockers used in the UK

Do alpha-blockers have side-effects?

Some people taking an alpha-blocker will ­experience side-effects. There is no way to predict if you will or not, until you start taking them.

Possible side-effects of alpha-blockers include:

• sudden drops in blood pressure when ­sitting up or standing up
• headaches or nausea
• swollen legs or ankles
• tiredness, weakness or feeling lethargic
• sleep disturbance
• tremor
• rash or itchiness of the skin
• rarely, they may cause problems with erections in men.

Centrally-acting drugs (central alpha antagonists)

Centrally-acting drugs work directly on the part of the brain that controls blood pressure. They soften the force of your heart beat and block nerve ­signals that can narrow your smaller blood vessels. These actions make it easier for blood to flow which helps lower your blood pressure.

Who might be given centrally-acting drugs?

You would rarely be given a centrally-acting drug as a first choice of medicine for high blood ­pressure. They would normally be used as a third or fourth choice. However, if you are pregnant or planning a pregnancy you may be given a ­medicine called methyldopa as it has been shown to be safe during pregnancy and breastfeeding.

Who would not be given ­centrally-acting drugs?

If you have heart disease, angina, kidney or liver disease, Parkinson’s disease or a history of ­depression you may need to be monitored closely while taking these medicines. Some centrally-acting drugs may interfere with tests for phaeo­chromo­cytoma.

Centrally-acting drugs used in UK

Do centrally acting drugs have side-effects?

Some people taking a centrally-acting drug will ­experience side-effects. There is no way to predict if you will or not, until you start taking them.

Possible side-effects of ­centrally-acting drugs include:

• feeling drowsy, tired, or dizzy
• dry mouth 
• upset stomach or nausea
• swollen legs or feet
• headache
• sleep disturbance

Less common side-effects may be depression, anxiety and problems with erections in men.

Methyldopa can sometimes cause liver problems. If you experience a fever after taking this medicine you should report it immediately. It may also ­trigger postural hypotension (a sudden drop in blood pressure when sitting up or standing up) or a slow heartbeat.

Direct-acting vasodilators

Direct-acting vasodilators relax the muscles in your blood vessel walls. This allows the blood vessels to widen and makes it easier for blood to flow. This effect lowers your blood pressure.

Who might be given direct-acting vasodilators?

You would rarely be given a vasodilator as a first choice of medicine for high blood pressure. They would normally be used as a third or fourth. One medicine called hydralazine may be given to ­people who have heart failure.

Who would not be given direct-acting vasodilators?

If you are pregnant, breastfeeding or planning a pregnancy, you should not be given a vasodilator.

If you have heart disease, angina, diabetes or ­uremia (build up of waste in your blood) you may not be given a vasodilator, or will need to be closely monitored. Caution may also be required if you have recently had a stroke or heart attack or if you have kidney disease. If you have a phaeo­chromocytoma you will not be given a vasodilator.

Direct-acting vasodilators used in the UK

Do direct-acting vasodilators have side-effects?

Some people taking a vasodilator will experience side-effects. There is no way to predict if you will or not, until you start taking them.

Possible side-effects of ­direct-acting vasodilators include:

• headaches
• a flushed appearance or skin rashes
• rapid or irregular heart beat
• weight gain
• swelling of feet or lower legs
• upset stomach
• excess body hair growth (with minoxidil)

Less commonly, you may experience chest pain, shortness of breath or numbness.

Aliskiren (Rasilez)

Aliskiren (brand name Rasilez) is a new type of blood pressure medicine called a “direct renin ­inhibitor”.

Aliskiren works by blocking the effects of a ­chemical called renin. Renin is involved in producing a hormone called angiotensin, which raises your blood pressure. By blocking renin, aliskiren reduces the amount of angiotensin in your body.

Who might be given aliskiren?

Aliskiren is not usually given as a first choice of blood pressure medicine. You would only usually be given it if you are not already taking an ACE ­inhibitor or an angiotensin receptor blocker (ARB).

Who would not be given aliskiren?

If you are pregnant, breastfeeding or planning a pregnancy, you should not be given aliskiren.

You may not be given this kind of medicine if have kidney problems, diabetes or hyperkalaemia (high potassium levels in your blood). If you have heart failure, severe kidney impairment or a history of dialysis then you may need to be monitored closely.

Does it have side-effects?

Aliskiren is a relatively new medicine and not much is yet known about its possible side-effects. As with all medicines, there is no way to predict if you will experience side effects or not, until you start taking the medicine.

The most common known side-effect of aliskiren is diarrhoea. Other less common side-effects include: 

• headache
• inflammation of the nasal passages
• skin rash
• swelling of the limbs.

Other things to be aware of about non-standard medicines

You may wish to ask your doctor for advice on when and how to take your medicines. For ­example, it may be better to take an alpha-blocker before going to bed rather than in the morning. This is because it can cause problems with ­dizziness. Other medicines may affect your ability to drive or to use heavy machinery. Others can be affected if you drink alcohol.

Check with your doctor or pharmacist before ­taking any other medicines in combination with your non-standard medicine – this includes over-the-counter treatments. Your doctor will not give you a non-standard medicine if they feel that it could conflict with other conditions that you have or other medicines that you are taking.

As with other blood pressure lowering medicines, once you start taking your medicine (whichever it may be), be prepared to stay on it for the long term. Some people stop taking their blood ­pressure medicines when they think their blood pressure is under control, but doing this can put your health at risk.  If you have any concerns about your medicine, speak to your doctor or pharmacist.

Published May 2009