It's more common to classify vasodilator drugs based on the way they work to widen blood vessels. Some act directly on blood vessels, making them relax and become wider. Others inhibit specific actions of the body that would cause the blood vessels to tighten and become narrower.
Many vasodilator drugs have other effects that can sometimes provide additional benefits. For example, some calcium channel blockers not only dilate blood vessels but also lessen the heart's mechanical and electrical functions, which in turn can enhance their blood-pressure-lowering action and may also help regulate arrhythmias (irregular heart rhythms).
Doctors decide which type of vasodilator drug to prescribe based on medical history, current symptoms and other medical conditions. Vasodilator drugs are rarely used alone -- they're usually prescribed in combination with other types of blood pressure drugs.
Once people who have high blood pressure begin taking vasodilator drugs, they generally need to keep taking them for the rest of their lives. Without these medicines, they would be at risk of developing serious health problems. And medicine alone may not be enough. People who are taking vasodilator drugs are usually encouraged by their doctors to make healthy lifestyle changes, like eating a heart-healthy diet, getting regular exercise and practicing stress-management techniques.