Vasodilators are medications that open (dilate) the blood vessels. As a result, the heart does not need to work as hard to pump blood through the blood vessels. Because there is less force in the blood vessels, blood pressure is lowered. Therefore, vasodilators are often prescribed to treat high blood pressure (hypertension), as well as to relieve symptoms associated with congestive heart failure.
Patients who are taking vasodilators are usually encouraged by their physician to make healthy lifestyle changes to help control their blood pressure. These lifestyle changes include eating a heart-healthy diet, getting regular exercise and practicing stress management techniques.
In addition to making healthy lifestyle changes, patients are generally encouraged to avoid other vasodilators, excessive alcohol use and grapefruit juice. All of these substances have been associated with very low blood pressure (hypotension) when used by people who are taking vasodilators.
In general, vasodilators (especially ACE inhibitors) should be avoided by women who are pregnant or breast feeding. Children and the elderly may also face special considerations when taking this type of medication.
About vasodilators
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.
Potential side effects with vasodilators
Below is a listing of side effects that are common to most vasodilators:
Allergic reaction (sneezing, respiratory congestion, itching or skin rashes)
Low blood pressure (hypotension)
Palpitations (pounding heart beat)
Dizziness or lightheadedness
Arrhythmia (abnormal heart rhythm)
Shallow, dry cough
Fainting (syncope)
Headache
Weight gain
Fluid retention
Drowsiness, weakness or fatigue
Abdominal discomfort
Increased sensitivity to sunlight (photosensitivity), causing severe sunburn or rash
Back or joint pain
Unusual bleeding (e.g., nosebleeds)
Unusual changes in appearance of skin (rash, blue tinge or yellow tinge [jaundice])
Drug or other interactions with vasodilators
Patients should consult their physician before taking any other medication (either prescription or over-the-counter), including nutritional supplements or herbal remedies. Substances that can intensify the effects of vasodilators and lead to severe hypotension (low blood pressure) include:
Other vasodilators or antihypertensives, unless prescribed as part of a combination therapy.
Alcohol, which is itself a vasodilator.
Medications for sexual dysfunction.
Nicotinic acid. A form of vitamin B3 that is sometimes used as a cholesterol-reducing drug.
Grapefruit juice. Grapefruit juice interferes with the liver’s ability to rid the body of vasodilators and many other substances. This could lead to a buildup of vasodilators to dangerous levels in the body. While the buildup is less likely if the juice is ingested four or more hours prior to the medicine, patients taking vasodilators are advised to speak with their physicians before drinking grapefruit juice or eating grapefruit itself.
The following substances may counteract the effects of some vasodilators and increase blood pressure:
Narcotics (prescription-strength painkillers)
Nicotine
Nonsteroidal anti-inflammatory drugs (NSAIDs)
In addition, some over-the-counter medications may adversely react with vasodilators, including those for appetite control, asthma, flu, colds, cough, sinus problems or hay fever.
Conditions of concern with vasodilators
In general, people are encouraged to discuss with their physician the risks and benefits of taking vasodilators if they have the following conditions:
Liver or kidney disease
Diabetes mellitus
Systemic lupus erythematosus (SLE)
Severe anemia
Glaucoma
Recent stroke or head injury
Over-active thyroid (hyperthyroidism)
Lifestyle considerations with vasodilators
Most patients taking vasodilators will be on the medication for a prolonged period, provided no serious side effects occur. Patients should remember that vasodilators control certain conditions, but do not cure them. Even if all their symptoms are relieved, patients should continue to take their medication exactly as directed and keep all scheduled follow-up appointments with their physician. In addition to taking medication, patients may be advised to make lifestyle modifications, especially those concerning diet, exercise and stress management.
Pregnancy use issues with vasodilators
Women who are pregnant or who may become pregnant should discuss the use of vasodilators with their physician before taking the medication. While some medication can be used during preganancy to treat pregnancy-induced hypertension, in most cases, women who are pregnant should avoid the use of vasodilators. This is especially true of ACE inhibitors, which can cause birth defects or death in the fetus if taken at any time during pregnancy. Women who become pregnant while taking ACE inhibitors should consult their physician immediately to discuss other methods of controlling high blood pressure.
ACE inhibitors and other types of vasodilators may also cause jaundice, blood problems and signs of low potassium levels in newborns.
Women who are breast feeding may be advised to avoid taking vasodilators, especially in the first month of nursing. Some types of vasodilators pass into breast milk and may be harmful for nursing children. Thiazide diuretics, in particular, may result in decreased flow of breast milk if taken during the first month of nursing.
Child use issues with vasodilators
Researchers have not yet fully examined the effect of vasodilators in children. In general, children tend to be more sensitive to the effects of medication than adults. Parents should consult a physician about using vasodilators to treat their child’s condition.
Elderly use issues with vasodilators
In general, elderly patients tend to be more sensitive to the side effects of vasodilators, especially dizziness and lightheadedness. Physicians may suggest that elderly patients start on a low dose of vasodilators until the full extent of any side effects are known.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians about their conditions. Patients may wish to ask their doctors the following questions related to vasodilators:
Why do I need a vasodilator?
Is this type better than any other antihypertensive for my high blood pressure?
If the side effects of one vasodilator are too much, can I switch to another?
How can I tell if this medication is working?
How often do I need to be monitored while on this medication?
Do any of my other regular medications interact with these drugs?
If I make lifestyle changes in diet and stress levels, can I stop taking this medication?
Are there any nutritional supplements I can take with this medication?
How much can I expect this drug to reduce my blood pressure?
