Medicine for High Blood Pressure

Which medicines are used to lower blood pressure?

There are five main classes of medicines that are used to lower blood pressure:

• Angiotensin-converting enzyme (ACE) inhibitors.
• Angiotensin receptor blockers (ARBs).
• Calcium-channel blockers.
• 'Water' tablets (thiazide diuretics).
• Beta-blockers.

The following gives a brief overview of each of the classes.

Angiotensin-converting enzyme (ACE) inhibitors

ACE inhibitors work by reducing the amount of a chemical, called angiotensin II, that you make in your bloodstream. This chemical tends to narrow (constrict) blood vessels. If there is less of this chemical, the blood vessels relax and widen and so the pressure of blood within the blood vessels is reduced.

An ACE inhibitor is particularly useful if you also have heart failure or diabetes. They are often used for people with chronic kidney disease. ACE inhibitors are not used in pregnant or breastfeeding women. You will need a blood test before starting an ACE inhibitor. This will check that your kidneys are working well. The blood test is repeated within two weeks after starting the medicine and within two weeks after any increase in dose. Then, a yearly blood test is usual.

For more information see the separate leaflet called ACE Inhibitors.

Angiotensin receptor blockers (ARBs)

These medicines are sometimes called angiotensin-II receptor antagonists. There are various types and brands. The ones available in the UK are: azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan and valsartan. They work by blocking the effect of angiotensin II on the blood vessel walls. So, they have a similar effect to ACE inhibitors (described above) and you will need blood tests at the same times as your would if you were taking ACE inhibitors.

Calcium-channel blockers

Calcium-channel blockers affect the way calcium is used in the blood vessels and heart muscle. This has a relaxing effect on the blood vessels. Calcium-channel blockers can also be used to treat angina.

For more information see the separate leaflet called Calcium-channel Blockers.

'Water' tablets

'Water' tablets (diuretics) work by increasing the amount of salt and fluid that you pass out in your urine. This has some effect on reducing the fluid in the circulation, which reduces blood pressure. They may also have a relaxing effect on the blood vessels, which reduces the pressure within the blood vessels.

The most commonly used diuretics to treat high blood pressure (hypertension) in the UK are thiazides or thiazide-like diuretics. Only a low dose of a diuretic is needed to treat high blood pressure. Therefore, you will not notice much diuretic effect (that is, you will not pass much extra urine). Thiazides are often the preferred treatment if you can't tolerate other types of medicine or if you have heart failure.

You will need a blood test before starting a diuretic, to check that your kidneys are working well. You should also have a blood test within 4-6 weeks of starting treatment with a diuretic, to check that your blood potassium has not been affected. Then, a yearly blood test is usual.

For more information see the separate leaflet called Thiazide Diuretics.

Beta-blockers

Beta-blockers are no longer usually used for blood pressure treatment alone. This is because they have been found to be less effective in preventing strokes and heart attacks than other medication choices. However, sometimes they may be used where there are other conditions present, such as heart failure or atrial fibrillation.

They work by slowing the heart rate, and reducing the force of the heart. These actions lower the blood pressure. Beta-blockers are also commonly used to treat angina and some other conditions. You should not normally take a beta-blocker if you have asthma, chronic obstructive pulmonary disease (COPD), or certain types of heart or blood vessel problems.

For more information see the separate leaflet called Beta-blockers.

What about side-effects?

All medicines have possible side-effects, and no medicine is without risk. However, most people who take medicines to lower blood pressure do not develop any side-effects, or only have mild side-effects. A full list of cautions and possible side-effects is listed on the leaflet inside the medicine packet. The most common ones are:

• ACE inhibitors - sometimes cause an irritating cough.
• ARBs - sometimes cause dizziness.
• Calcium-channel blockers - sometimes cause dizziness, facial flushing, swollen ankles, and constipation.
• 'Water' tablets (diuretics) - can cause gout attacks in a small number of users, or can make gout worse if you already have gout. Erection problems (impotence) develop in some users.
• Beta-blockers - can cause cool hands and feet, poor sleep, tiredness and impotence in some users.

If you do develop a side-effect, a different medicine may suit you better. There is a lot of choice so one can usually be found to suit. See your doctor if you develop any problem which you think is due to your medication.

Other medicines for high blood pressure

Apart from the five main classes of medicines listed above, sometimes other medicines are used to lower blood pressure. For example:

Methyldopa or alpha-blockers are sometimes used if there are problems with the more commonly used medicines. Doxazosin is an alpha-blocker commonly added when blood pressure is high despite the treated person being on other medicines.

Spironolactone is another stronger 'water' tablet (diuretic) sometimes used as an add-on option for blood pressure which is difficult to control. Spironolactone is not usually given alongside ACE inhibitors or ARBs because the combination can cause potassium levels in the body to become dangerously high. Regular blood tests to check for this are needed if you are on this medication or medicine combination.

Combinations of medicines

One medicine alone may not be enough. One medicine alone can reduce high blood pressure (hypertension) to the target level in less than half of cases. It is common to need two or more different medicines to reduce high blood pressure to a target level. In about a third of cases, three medicines or more are needed to get blood pressure to the target level.

So, for example, you may need an ACE inhibitor plus a calcium-channel blocker (and sometimes also another medicine) to control your blood pressure. This is just an example, and various combinations of medicines can be used.

In some cases, despite treatment, the target level is not reached. However, although to reach a target level is ideal, you will gain benefit from any reduction of high blood pressure.

So, which is the best medicine or combination of medicines?

The one or ones chosen may depend on factors such as:

• Whether you have other medical problems.
• Your ethnic origin.
• Whether you take other medication.
• Possible side-effects.
• Your age.

For example:

• Beta-blockers and calcium-channel blockers can also treat angina.
• ACE inhibitors also treat heart failure.
• Some medicines are not suitable if you are pregnant.
• Some medicines are thought to be better if you have diabetes.
• Some medicines tend to work better than others in people of Afro-Caribbean origin.

If you do not have any other medical problems that warrant a particular medicine then current UK guidelines give the following recommendations as to usual medicines that should be used. These recommendations are based on treatments and combinations of treatments that are likely to give the best control of the blood pressure with the least risk of side-effects or problems.

Treatment is guided by the A/C, A+C, A+C+D approach, where:

• A = ACE inhibitor or ARB.
• C = calcium-channel blocker.
• D = diuretic.

The suggested stepwise approach is as follows:

• If you are less than 55 years old and are not of black African or Caribbean origin then your doctor may begin treatment with an 'A' (an ACE inhibitor, or an ARB if an ACE inhibitor causes problems or side-effects).
• If you are 55 years or older, or are of black African or Caribbean origin then your doctor may begin treatment with a 'C' (a calcium-channel blocker).
• Then, if your blood pressure has not reached the target, your doctor may combine 'A' with 'C' (an ACE inhibitor or an ARB plus a calcium-channel blocker). The National Institute for Health and Care Excellence (NICE) recommend that ARBs may work better than ACE inhibitors in people of black African or Caribbean origin.
• If your target blood pressure is still not reached, your doctor may combine 'A' with 'C' and 'D' (that is, adding a diuretic).
• Many people of black African or Caribbean origin have high blood pressure, and most need two or more medicines to control their blood pressure. One study found that a combination of amlodipine (a 'C'' drug) with perindopril (an 'A' drug) or hydrochlorothiazide (a 'D' drug) was more effective at controlling blood pressure than the A drug combined with the D drug.
• If a fourth medicine is needed to achieve the target blood pressure, your doctor may add one of the following:
• A beta-blocker.
• Another diuretic.
• An alpha-blocker.

However, individuals can vary. Sometimes, if one medicine does not work so well or causes side-effects, a switch to a different class of medicine may work well.

How long is medication needed for?

In most cases, medication is needed for life. However, in some people whose blood pressure has been well controlled for three years or more, medication may be able to be stopped. In particular, this may be possible for people who have made significant changes to lifestyle (such as having lost a lot of weight, or stopped heavy drinking, etc). Your doctor can advise you.

If you stop medication, you should have regular blood pressure checks. In some cases the blood pressure remains normal. However, in others it starts to rise again. If this happens, medication can then be started again.