Corgard

Definition

Antihypertensive drugs are medicines that help lower blood pressure.

Purpose

Antihypertensive drugs are used to help control blood pressure in people whose blood pressure is too high. Blood pressure is a measurement of the force with which blood moves through the body's system of blood vessels. Although everyone's blood pressure goes up and down in the course of a typical day -- getting higher when they are active and going down when they sleep -- some people have blood pressure that stays high all the time. This condition is known as hypertension. Hypertension is not the same as nervous tension. People who have high blood pressure are not necessarily tense, high-strung, or nervous. They may not even be aware of their condition.

Being aware of high blood pressure and doing something to control it are extremely important, however. Untreated, high blood pressure can lead to diseases of the heart and arteries, kidney damage, or stroke, and can shorten life expectancy.

Treatments for high blood pressure depend on the type of hypertension. Most cases of high blood pressure are called essential or primary hypertension, meaning that the high blood pressure is not caused by some other medical condition. For most people with primary hypertension, it is difficult to figure out the exact cause of the problem. However, such hypertension usually can be controlled by some combination of antihypertensive drugs and changes in daily habits (such as diet, exercise, and weight control).

In people with secondary hypertension, the high blood pressure may be due to medical problems such as kidney disease, narrowing of certain arteries, or tumors of the adrenal glands. Correcting these problems often cures the high blood pressure, and no further treatment is needed.

Controlling primary hypertension, on the other hand, is usually a lifelong commitment. Although people may be able to reduce the amount of medicine they take as their blood pressure improves, they usually must continue taking it for the rest of their lives.

Description

Many different types of drugs are used, alone or in combination with other drugs, to treat high blood pressure. The major categories are:

• Angiotensin-converting enzyme inhibitors, such as benazepril (Lotensin), captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), quinapril (Accupril), and ramipril (Altace). ACE inhibitors work by preventing a chemical in the blood, angiotensin I, from being converted into a substance that increases salt and water retention in the body. These drugs also make blood vessels relax, which further reduces blood pressure.
• Angiotensin II receptor antagonists, such as losartan (Cozaar) and losartan with hydrochlorothiazide (Hyzaar). These drugs act at a later step in the same process that ACE inhibitors affect. Like ACE inhibitors, they lower blood pressure by relaxing blood vessels.
• Beta blockers, such as atenolol (Tenormin), metoprolol (Lopressor), nadolol (Corgard), propranolol (Inderal), and timolol (Blocadren). Beta blockers affect the body's response to certain nerve impulses. This, in turn, decreases the force and rate of the heart's contractions, which lowers blood pressure.
• Blood vessel dilators (vasodilators), such as hydralazine (Apresoline) and minoxidil (Loniten). These drugs lower blood pressure by relaxing muscles in the blood vessel walls.
• Calcium channel blockers, such as amlopidine (Norvasc), diltiazem (Cardizem), isradipine (DynaCirc), nifedipine (Adalat, Procardia), and verapamil (Calan, Isoptin, Verelan). Drugs in this group slow the movement of calcium into the cells of blood vessels. This relaxes the blood vessels and lowers blood pressure.
• Diuretics, such as chlorthalidone (Hygroton), furosemide (Lasix), hydrochlorothiazide (Esidrix, HydroDIURIL), and metolazone (Zaroxolyn). These drugs control blood pressure by eliminating excess salt and water from the body.
• Nerve blockers, such as alpha methyldopa (Aldomet), clonidine (Catapres), guanabenz (Wytensin), guanadrel (Hylorel), guanethidine (Ismelin), prazosin (Minipress), rauwolfia derivatives (Reserpine), and terazosin (Hytrin). These drugs control nerve impulses along certain nerve pathways. This allows blood vessels to relax and lowers blood pressure.

Recommended dosage

The recommended dosage depends on the type, strength, and form of antihypertensive drug. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage.

Always take antihypertensive drugs exactly as directed. Never take larger or more frequent doses, and do not miss any doses. Some antihypertensive drugs may take several weeks to noticeably lower blood pressure. Be patient and give the medicine time to work. Once it begins to work and symptoms improve, continuing to take the medicine is just as important.

Stopping some hypertensive drugs suddenly may cause serious problems. Check with the physician who prescribed the medicine to find out if it is necessary to gradually taper down before stopping the medicine completely.

Precautions

Finding an effective combination of medicines and lifestyle changes for each patient can take time. Patients and their health care providers must work closely together during this process.

People who have high blood pressure often feel perfectly fine. However, they should continue to see their physicians even when they feel well so that the physician can keep a close watch on their condition. Patients should also keep taking their medicine even when they feel fine.

Antihypertensive drugs will not cure high blood pressure, but will help control the condition. To avoid the serious health problems that high blood pressure can cause, patients may have to take medicine for the rest of their lives. Furthermore, medicine alone may not be enough. People with high blood pressure also may need to avoid certain foods and keep their weight under control. The health care professional who is treating the condition can offer advice on what measures may be necessary. Patients being treated for high blood pressure should not change their diets without consulting their physicians.

Anyone taking antihypertensive drugs should not take any other prescription or over-the-counter medicine without first checking with his or her physician. Some medicines may increase blood pressure.

Side effects

Many patients who take antihypertensive drugs are not bothered by side effects. For some, however, the side effects are troublesome, especially when they felt fine before starting to take the drugs. Remember that the benefits of controlling high blood pressure far outweigh the risks of side effects. Knowing in advance what side effects are possible and how to deal with them if they occur may make them easier to cope with.

Interactions

Antihypertensive drugs may interact with many other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone taking antihypertensive drugs should not take any other prescription or nonprescription (over-the-counter) medicine without first checking with his or her physician.

Key Terms

Arteries

Blood vessels that carry blood away from the heart to the cells, tissues, and organs of the body.

Stroke

A serious medical event in which blood flow to the brain is stopped. This may be because of a blood clot in an artery or because an artery has burst. Strokes may cause paralysis, changes in speech, memory, and behavior or death.

Further Reading

For Your Information

Organizations

• National High Blood Pressure Education Program. 4733 Bethesda Avenue, Suite 530, Bethesda, MD 20814-4820.

Gale Encyclopedia of Medicine. Gale Research, 1999.