Medication for High Blood Pressure

What is the aim of treatment?

• The usual target is to reduce blood pressure to 140/90 or below.
• In some cases, the target is to get it below 130/80 mmHg. For example, if you have a cardiovascular disease such as a stroke or heart disease, if you have certain kidney diseases, and for some people with diabetes.

Which drugs are used to lower blood pressure?

There are five main classes of drugs that are used to lower blood pressure. There are various types and brands of drug in each class. The following gives a brief overview of each of the classes. However, for detailed information about your own medication you should read the leaflet that comes inside the drug packet.

Angiotensin-converting enzyme (ACE) inhibitors

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

There are various types and brands of ACE inhibitors. For example, captopril, cilazapril, enalapril, fisinopril, lisinopril, perindopril, quinapril, ramipril, and trandolapril. An ACE inhibitor is particularly useful if you also have heart failure or diabetes. ACE inhibitors should not be taken by people with certain types of kidney problems, people with some types of artery problems, and if you are pregnant. You will need a blood test before starting an ACE inhibitor to check that your kidneys are working well. The blood test is repeated within two weeks after starting the drug, and within two weeks after any increase in dose. Then, a yearly blood test is usual.

Angiotensin Receptor Blockers

These drugs are sometimes called angiotension II receptor antagonists. There are various types and brands. For example, 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).

Calcium-channel blockers

These drugs affect the way calcium is used in the blood vessels and heart muscle. This has a relaxing effect on the blood vessels. Again, there are various types and brands. For example, amlodipine, diltiazem, felodipine, isradipine, lacidipine, lercanidipine, nicardipine, nifedipine, nisoldipine, and verapamil. Calcium-channel blockers can also be used to treat angina.

Diuretics ('water tablets')

The most commonly used diuretic to treat high blood pressure in the UK is called bendroflumethiazide - but there are others. For example, chlorothiazide, chlorthalidone, cyclopenthiazide, hydrochlorothiazide, and indapamide. 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. 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). 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 to check that your blood potassium has not been affected within 4-6 weeks of starting treatment with a diuretic. Then, a yearly blood test is usual.

Beta-blockers

Again, there are various types and brands. For example, acebutolol, atenolol, bisoprolol, metoprolol, oxprenolol, pindolol, propanaolol, sotalol, and timolol. 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 take a beta-blocker if you have asthma, chronic obstructive pulmonary disease (COPD), or certain types of heart or blood vessel problems.

What about side-effects?

All drugs have possible side-effects, and no drug is without risk. However, most people who take drugs 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 drug packet. The most common ones are:

• ACE inhibitors - sometimes cause an irritating cough.
• Angiotensin receptor blockers - sometimes cause dizziness.
• Calcium channel blockers - sometimes cause dizziness, facial flushing, swollen ankles, and constipation.
• Diuretics - can cause gout attacks in a small number of users, or can make gout worse if you already have gout. Impotence develops 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 drug 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 drugs for high blood pressure

Apart from the five main classes of drugs listed above, sometimes other drugs are used to lower blood pressure. For example, methyldopa or alpha blockers are sometimes used if there are problems with the more commonly used drugs.

Combinations of drugs

One drug can reduce high blood pressure to the target level in less than half of cases. It is common to need two or more different drugs to reduce high blood pressure to a target level. In about a third of cases, three drugs 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 drug) to control your blood pressure. This is just an example, and various combinations of drugs 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 some benefit from any reduction of high blood pressure.

So, which is the best drug or combination of drugs?

The one or ones chosen may depend on such things as: if you have other medical problems; your ethnic origin; if you take other medication; possible side-effects; your age; etc.

For example: beta-blockers and calcium channel blockers can also treat angina; ACE inhibitors also treat heart failure; some drugs are not suitable if you are pregnant; some are thought to be better if you have diabetes; some tend to work better than others in people of Afro-Caribbean origin; etc.

If you do not have any other medical problems that warrants a particular drug, then current UK guidelines give the following recommendations as to usual drugs 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/CD approach as follows:

• If you are less than 55 years old and are not of black African or Caribbean origin then initial treatment should be with 'A' (an ACE inhibitor, or an angiotensin receptor blocker 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 initial treatment should be with 'C' or 'D' (a calcium-channel blocker or a diuretic).
• Then, if the target blood pressure is not reached, combine 'A' with 'C' or 'D' (an ACE inhibitor or an angiotensin receptor blocker plus a calcium-channel blocker or diuretic).
• Then, if target blood pressure is still not reached, combine 'A' with 'C' and 'D' (an ACE inhibitor or an angiotensin receptor blocker, and a calcium-channel blocker, and a diuretic).
• If a fourth drug is needed to achieve the target blood pressure, consider adding of one of the following:
  • A beta-blocker
  • Another diuretic
  • An alpha-blocker

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

How long is medication for high blood pressure 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, in people who have made significant changes to lifestyle which can affect blood pressure (such as lost a lot of weight, or stopped heavy drinking, etc). Your doctor can advise. If you stop medication, you need regular blood pressure checks. In some cases the blood pressure remains normal. However, in others it starts to rise again. Medication can then be started again.

Further help and information

Blood Pressure Association

60 Cranmer Terrace, London, SW17 0QS
Tel: 020 8772 4994 Web: www.bpassoc.org.uk

High Blood Pressure Foundation

Dept of Medical Sciences, Western General Hospital, Edinburgh, EH4 2XU
Tel: 0131 332 9211 Web: www.hbpf.org.uk