Drugs used to treat high blood pressure, a condition also known as hypertension
Centrally acting drugs
Other antihypertensive drugs
High blood pressure (see Hypertension) requires treatment mainly because it increases the risk of both coronary artery disease and stroke. Antihypertensive drugs are most often used when changes in your lifestyle, such as improving your diet, doing more exercise, and giving up smoking, fail to produce an adequate fall in blood pressure over a short period of time. Antihypertensives are also used to treat hypertension in pregnancy (see Pre-eclampsia and eclampsia).
What are the types?
There are many different types of antihypertensive drugs. The types that are most commonly used are beta-blocker drugs, ACE inhibitor drugs, angiotensin II blocker drugs, calcium channel blocker drugs, and diuretic drugs. Less commonly, alpha-blocker drugs, centrally acting drugs, and other drugs, including diazoxide, hydralazine, and minoxidil, are used.
Most types of antihypertensive drug reduce high blood pressure by increasing the diameter of the blood vessels (a process known as vasodilation) or by reducing the force with which the heart pumps the blood. ACE inhibitors, alpha-blockers, angiotensin II blockers, calcium channel blockers, and centrally acting drugs act in a variety of ways to cause vasodilation. Beta-blockers lower blood pressure by reducing the force with which the heart pumps. This effect is achieved by blocking the action of substances produced naturally by the body that increase heart rate and blood pressure. Diuretics cause the kidneys to excrete more water and salts than usual, which reduces the volume of blood that is present in the circulation and thereby lowers blood pressure.
How are they used?
Antihypertensives are normally taken orally over long periods of time and often for life. However, in some cases it is possible to reduce the dose gradually and eventually stop the drugs if blood pressure returns to normal following long-term changes in weight or lifestyle. The choice of drug depends on several factors, including age, other medical conditions that might be present, and severity of the high blood pressure. Certain drugs are especially likely to cause side effects in elderly people.
At the beginning of treatment for mild or moderate hypertension, a single drug is usually used. For some people this may be an ACE inhibitor or angiotensin II blocker, whereas for others the initial treatment may be with a calcium channel blocker or diuretic. If a single drug does not reduce your blood pressure sufficiently, a combination of these drugs may be used. Some people who have moderate hypertension also require an additional drug, in which case an alpha-blocker or beta-blocker may also be prescribed.
If you have mild or moderate hypertension, your doctor will usually start you on a low dose of a drug. The dose is then gradually increased until your blood pressure is normal or until you experience side effects.
People with severe hypertension are usually treated with a combination of several drugs, which may need to be given in high doses. Your doctor may need to try a number of drugs before finding a combination that controls your blood pressure without producing unacceptable side effects.
Everybody receiving treatment for hypertension will have their blood pressure monitored regularly.
What are the side effects?
All antihypertensive drugs, in particular ACE inhibitors and alpha-blockers, can cause a sudden drop in blood pressure (see Hypotension) when you first take them. This drop in blood pressure can cause light-headedness. Some drugs may also cause drowsiness. If you experience these side effects, your doctor may reduce the dose or may give you a different drug. You should not stop taking an antihypertensive without first consulting your doctor.
Other side effects are associated with specific types of antihypertensive drugs. Several types of these drugs, especially beta-blockers and some diuretics, may cause erectile dysfunction; ACE inhibitors sometimes cause a dry cough and calcium channel blockers may cause swollen ankles, flushing, and headaches. Long-term use of diuretics may increase the risk of gout. Minoxidil may result in excessive hair and hydralazine may cause palpitations.
Do not suddenly stop taking an antihypertensive drug without first consulting your doctor. Abrupt withdrawal of the drug could cause a rapid increase in blood pressure.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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