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Vasodilators are agents that relax and widen blood vessels, allowing blood to flow more freely and the heart to pump more efficiently. These medications are prescribed to treat high blood pressure, sometimes in conjunction with other medications. Patients who are prescribed vasodilators may be on the medication for the rest of their lives.
While there are natural vasodilators in the body, the term usually refers to medications that produce the same response. Some vasodilators act directly on blood vessels, causing them to relax and widen. Others inhibit specific actions of the body that would cause the blood vessels to tighten and narrow. Examples of vasodilators include:
- ACE inhibitors (angiotensin-converting enzyme inhibitors). These medications block the production of a chemical (angiotensin II) that causes blood vessels to tighten. By preventing this constriction, more blood can flow into the systemic circulation. As a result, the heart’s workload is decreased. Examples of ACE inhibitors include benazepril, captopril and ramipril.
- Angiotensin II receptor blockers (ARBs). These medications produce the same effect as ACE inhibitors but use a different mechanism. Instead of preventing the production of angiotensin II, they inhibit the action of this substance by blocking it from entering angiotensin II receptors in the smooth muscles of the systemic blood vessels. Indirectly, the heart’s workload is decreased. Examples of ARBs include losartan, olmesartan and irbersartan.
- Alpha blockers. These medications reduce the workload of the heart by blocking certain chemicals from entering systemic alpha receptors and, in some instances, the central nervous system and its receptors. Examples of alpha blockers include methyldopa, doxazosin and phenoxybenzamine.
- Calcium channel blockers. These medications reduce the workload of the heart by blocking calcium ions from signaling blood vessels to constrict. They have a direct slowing effect on the heart muscle. Examples include amlodipine and felodipine.
- Nitrates. These medications work both by dilating the veins of the body to allow blood to pool and by working directly on the smooth muscles of the coronary blood vessels, causing them to relax and increasing the flow of oxygen-rich blood to the heart. Examples include isosorbide dinitrate, isosorbide mononitrate and methylclothiazide.
- Thiazide diuretics. There are four types of diuretics: loop, potassium-sparing, osmotic and thiazide. Sometimes called “water pills,” these medications promote the formation of urine in the kidneys, causing the body to flush out fluids and minerals including sodium. Low-dose thiazide diuretics are the only member of this group that also work as vasodilators. Examples of thiazide diuretics include bendroflumethiazide, hydrochlorothiazide and methylclothiazide.
- Central adrenergic inhibitors. These medications affect the signals from the brain and prevent them from narrowing blood vessels. They may also be used for other conditions, including panic attacks and migraine headaches. Examples include clonidine and guanfacine.
Most vasodilators have at least some antihypertensive properties because they widen blood vessels enough to significantly lower the patient’s blood pressure. Physicians choose the type of vasodilator based on each patient’s medical history, current symptoms and underlying associated conditions. | 
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