Vasodilators are medicines that act directly on muscles in blood vessel wallsto make blood vessels widen (dilate).

Vasodilators are used to treat high blood pressure (hypertension). By widening the arteries, these drugs allow blood to flow through more easily, reducingblood pressure. Controlling high blood pressure is important because the condition puts a burden on the heart and the arteries, which can lead to permanent damage over time. If untreated, high blood pressure increases the risk ofheart attacks, heart failure, stroke, or kidney failure. Vasodilators usuallyare prescribed with other types of blood pressure drugs and rarely are usedalone.

Examples of vasodilators are hydralazine (Apresoline) and minoxidil (Loniten). The vasodilator hydralazine also may be used to control high blood pressurein pregnant women or to bring down extremely high blood pressure in emergency situations. In the forms used for treating high blood pressure (tablets orinjections), these drugs are available only with a physician's prescription.A liquid form of minoxidil, used to promote hair growth in people with certain kinds of baldness and is applied directly to the scalp, is sold without a prescription.

Seeing a physician regularly while taking a vasodilator is important, especially during the first few months. The physician will check to make sure the medicine is working as it should and will watch for unwanted side effects. People who have high blood pressure often feel fine. But even when they feel well, patients should keep seeing their physicians and taking their medicine.

Vasodilators 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 may also need to avoid certain foods and keep their weight under control. The healthcare professional who is treating the condition can offer advice on what measures may be necessary.

Some people feel dizzy or have headaches while using this medicine. These problems are especially likely to occur in older people, who are more sensitivethan younger people to the medicine's effects. Anyone who takes these drugs should not drive, use machines, or do anything else that might be dangerous until they know how the drugs affect them.

People who have certain medical conditions or who are taking certain other medicines may have problems if they take vasodilators. Before taking these drugs, be sure to let the physician know about any of these conditions:

Anyone who has had an unusual reaction to a vasodilator in the past should let his or her physician know before taking this type of drug again. The physician should also be told about any allergies to foods, dyes, preservatives, orother substances.

Several problems--from excess hair growth to blood abnormalities--have been reported in babies whose mothers take this vasodilators during pregnancy. In studies of laboratory animals, hydralazine causes birth defects in mice and rabbits, but not in rats. The effects of taking vasodilators during pregnancy have not been specifically studied in humans. Women who are pregnant or who may become pregnant should check with their physicians before using this medicine. Women who become pregnant while taking a vasodilator should tell their physicians right away.

Using a vasodilator to lower blood pressure may worsen the problems that result from heart disease, blood vessel disease, or a recent heart attack or stroke. This medicine may also make angina (chest pain) worse. And in people withpheochromocytoma (tumor of the adrenal medulla), vasodilators may make the tumor more active. Before using a vasodilator, people with any of these medical problems should make sure their physicians are aware of their conditions.

Anyone who has unusual symptoms while taking a vasodilator should get in touch with his or her physician.

Vasodilators may interact with other medicines. Do not take any other medicine without the approval of the physician who prescribed the vasodilator. In particular, avoid using over-the-counter medicines for appetite control,colds, cough, sinus problems, asthma, hay fever and other allergies, as these may increase blood pressure. At the other extreme, dangerously low blood pressure may result when drugs such as the blood pressure medicine guanethidine(Ismelin) or nitrates, used to treat chest pain, are combined with vasodilators.

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