- What Are Vasodilators?
- Types of Vasodilators
- Common Vasodilators
- Side Effects of Vasodilators
- Vasodilator Precautions
- Vasodilators and Alcohol
- Vasodilators and Pregnancy
- What are peripheral vasodilators?
- When are peripheral vasodilators usually prescribed?
- How do peripheral vasodilators work?
- Which peripheral vasodilator is usually prescribed?
- How should I take peripheral vasodilators?
- What are the possible side-effects?
- Other considerations
- Can I buy peripheral vasodilators?
- Who cannot take peripheral vasodilators?
- Natural vasodilators to increase blood flow
- Nutrients for Lowering Blood Pressure
- Lifestyle Changes Are Safe, Effective, and Underutilized
- Supplements for Lowering Blood Pressure
- Vasodilator Drugs
- Therapeutic Uses of Vasodilators
- Side-Effects of Vasodilators
- Drug Classes and General Mechanisms of Action
- High Blood Pressure Medicines
What Are Vasodilators?
This class of drugs is often used to treat cardiovascular conditions, such as hypertension.
Vasodilators are a group of medicines that dilate (open) blood vessels, which allows blood to flow more easily.
They’re used to treat or prevent:
- High blood pressure (hypertension)
- Heart failure
- Preeclampsia (high blood pressure during pregnancy)
- Angina (chest pain caused by reduced blood flow to the heart)
- Pulmonary hypertension (high blood pressure that affects the arteries in your lungs)
Vasodilators are often combined with other drugs and are rarely used alone.
Types of Vasodilators
There are different types of vasodilators, including:
- Arterial dilators (mainly affect the arteries)
- Venous dilators (mainly affect the veins)
- Mixed dilators (affect veins and arteries)
Arterial dilators are typically prescribed to treat high blood pressure and heart failure, while venous dilators are effective for angina and heart failure.
Your doctor will decide which vasodilator is right for you.
The following are commonly prescribed vasodilators:
- ACE inhibitors
Side Effects of Vasodilators
Side Effects of vasodilators may include:
- Chest pain
- Heart palpitations (fluttering or pounding heartbeat)
- Rapid heartbeat
- Fluid retention
- Nausea or vomiting
- Excessive hair growth
- Nasal congestion
Tell your doctor about any other medical conditions you have before starting on a vasodilator.
Vasodilators may help control your high blood pressure, but they won’t cure the condition.
Your doctor may suggest that you follow a special diet while taking vasodilators. Follow these instructions carefully.
Vasodilators can cause dizziness. Don’t drive or perform activities that require alertness until you know how these medicines affect you.
Tell your healthcare provider that you’re taking a vasodilator before having any type of medical procedure, including dental procedures.
Your doctor will want to perform frequent tests to monitor your body’s response to these medicines. Keep all appointments with your doctor’s office and laboratory.
Let your doctor know about all prescription, non-prescription, illegal, recreational, herbal, nutritional, or dietary drugs you’re taking before starting on a vasodilator.
Vasodilators and Alcohol
Alcohol may interfere with how vasodilators work in your body.
Avoid drinking alcohol while taking these medicines.
Vasodilators and Pregnancy
Tell your doctor if you’re pregnant or might become pregnant while taking a vasodilator.
Some of these medicines can cause unwanted effects in unborn babies.
You’ll have to discuss the risks and benefits of taking vasodilators during pregnancy.
Also, talk to your healthcare provider before taking a vasodilator if you’re breastfeeding.
Three months after the injections, another test, X-rays known as angiograms in which a radio-opaque chemical is injected to outline the coronary arteries, showed that no new blockages had developed.
No serious unwanted effects from the growth factor were seen in the 20 recipients, and all are alive, the German team reported in Circulation, a journal published by the American Heart Association in Dallas.
F.G.F.-1 has not been patented, Dr. Stegmann said in a telephone interview. If the growth factor proves its mettle in further tests and comes to market, it will be expensive, like other genetically engineered drugs, Dr. Stegmann said. But he said there was no way to put a dollar value on such potential therapy.
F.G.F.-1 is one of several substances that doctors are testing to try to grow new heart vessels. The need for such a procedure is particularly great among patients who have blocked arteries that are not amenable to bypass because they are so narrowed that surgeons cannot sew a vein or artery into them to bypass the obstruction.
Among others seeking to grow new blood vessels in diseased hearts is a team headed by Dr. Jeffrey M. Isner of St. Elizabeth’s Hospital in Boston. His team has used a different technique, known as gene therapy, to produce new blood vessels around blocked arteries in legs and is awaiting approval to use the same material (known as V.E.G.F. for vascular endothelial growth factor) in the heart.
At New York Hospital-Cornell Medical Center in New York, Dr. Wayne Isom’s team recently started testing gene therapy along with bypass surgery.
In Germany, the patients’ heart function improved as measured by a standard test known as the ejection fraction before and after the bypass and drug therapy. The test measures the amount of blood that the left ventricle, the heart’s main pumping chamber, expels with each beat and indicates how well it is pumping. An ejection fraction from 60 percent to 75 percent is considered normal, although some doctors lower the limit to 50 percent.
What are peripheral vasodilators?
Peripheral vasodilators are used in peripheral arterial disease (PAD) and intermittent claudication to try to open up (dilate) the arteries; this helps to increase the distance you can walk before pain develops.
In Raynaud’s phenomenon they are used to dilate the small blood vessels and prevent them from constricting. This helps to maintain the blood supply to the fingers, etc.
There are a number of peripheral vasodilators. They include, cilostazol, moxisylyte, naftidrofuryl, pentoxifylline and nifedipine. These medicines are available as tablets and capsules and come in various brand names.
Inositol nicotinate and pentoxifylline are not considered effective for PAD. Pentoxifylline and moxisylyte are not considered effective for Raynaud’s phenomenon.
When are peripheral vasodilators usually prescribed?
If your have intermittent claudication, a vasodilator is usually only prescribed if self-help measures such as exercise have not improved your symptoms and you do not wish to be considered for surgery. However, they do not work in all cases. Therefore, there is no point in continuing with these medicines if you do not notice an improvement in symptoms within a few weeks. If your symptoms do not improve, your doctor will usually advise you to stop treatment. If symptoms improve, you can continue with treatment. Your doctor will usually review your treatment regularly to ensure that it is still being of benefit.
If you have Raynaud’s phenomenon, nifedipine is usually only prescribed after self-help measures (such as keeping the whole body warm, including the hands and feet, and stopping smoking) have been tried and your symptoms have not improved. Usually a short course of nifedipine is prescribed to begin with. This is in order to see if nifedipine will work for you.
How do peripheral vasodilators work?
Peripheral vasodilators work in slightly different ways to one another.
- Cilostazol and inositol nicotinate work by widening the arteries that supply blood to the legs. Cilostazol also improves circulation by keeping platelets in the blood from sticking together and clotting.
- Naftidrofuryl works by widening blood vessels to improve the flow of blood to these areas and also by allowing your body to make better use of the oxygen in your blood.
- Nifedipine is a type of medicine called a calcium-channel blocker. It is sometimes used to treat high blood pressure but it is also a peripheral vasodilator. It works by widening the blood vessels and stopping them from going into a spasm or narrowing.
- Moxisylyte is a type of medicine called an alpha-blocker. It works by relaxing the blood vessels, which in turn maintains the supply of blood to the fingers, toes, ears or nose.
- Pentoxifylline works by decreasing the thickness of the blood. Blood is then able to flow more easily, especially in the small blood vessels of the hands and feet.
Which peripheral vasodilator is usually prescribed?
Peripheral arterial disease (PAD): national guidelines only recommend the use of naftidrofuryl for people with intermittent claudication caused by PAD. Other peripheral vasodilators are not normally prescribed because there is little evidence that any of the others work very well for this condition. However, cilostazol is licensed for the treatment of PAD in selected patients who do not respond to other treatments.
Raynaud’s phenomenon: nifedipine is recommended to reduce the number and severity of ‘vasospastic’ attacks – when the blood vessels become narrower (constrict). Other peripheral vasodilators are not normally prescribed, as there is a lack of any studies to show that they work very well for Raynaud’s phenomenon. Sometimes, if you cannot tolerate the side-effects of nifedipine, your doctor may consider prescribing a different calcium-channel blocker such as nicardipine, amlodipine or felodipine. These medicines are not licensed to treat Raynaud’s disease. Rarely, naftidrofuryl or inositol nicotinate may also be prescribed by some doctors to treat Raynaud’s phenomenon.
How should I take peripheral vasodilators?
How you take nifedipine will depend upon the pattern of your symptoms and how well your symptoms improve with treatment.
All other vasodilators are taken every day.
What are the possible side-effects?
Most people who take peripheral vasodilators have no side-effects, or only minor ones. It is not possible in this leaflet to list all the possible side-effects for these medicines. For more detailed information, see the leaflet that comes within the medicine packet.
Nifedipine – some people develop flushing and headache. Serious side-effects are rare.
Naftidrofuryl – the most commonly reported side-effects are feeling sick, skin rash, stomach pains and runny stools (diarrhoea). On rare occasions, some people taking naftidrofuryl have developed a liver disorder. If you notice any yellowing of your skin or the whites of your eyes, speak with your doctor straightaway.
Cilostazol – the most common side-effects include headache and diarrhoea. Less common side-effects include dizziness, weakness, feeling or being sick, indigestion, tummy (abdominal) pain, fast heartbeat, chest pain, runny nose, bruising, swollen ankles or feet, skin rash and itching.
Inositol nicotinate – side-effects are thought to be uncommon but may include flushing, dizziness, headache, feeling sick, being sick (vomiting), fainting and a rash.
Moxisylyte – the most common side-effects include mild nausea, diarrhoea, dizziness with a spinning sensation (vertigo), headache, facial flushing and a rash. On rare occasions, some people taking moxisylyte have developed a liver disorder. If you notice any yellowing of your skin or the whites of your eyes, speak with your doctor straightaway.
Pentoxifylline – the most common side-effects include nausea, vomiting, and dizziness which may occur. Uncommonly, some people experience a fast or irregular heartbeat.
If you are taking nifedipine, do not drink grapefruit juice. This can interact with the medicine and alter its effect.
Can I buy peripheral vasodilators?
No – you cannot buy oral peripheral vasodilators; you need a prescription to obtain these medicines.
Who cannot take peripheral vasodilators?
Most people are able to take a peripheral vasodilator; however, in some cases these medicines are best avoided.
Nifedipine – should not be given to people who:
- Have severe damage to the heart muscle (cardiogenic shock).
- Have a valve in the heart that does not open fully (advanced aortic stenosis).
- Are within one month of having had a heart attack.
- Have acute attacks of angina.
Naftidrofuryl – should not be given to people with a history of kidney stones.
Cilostazol – should not be given to people with:
- Severe kidney or liver problems.
- Heart failure.
- Heart rhythm problems.
- Uncontrolled high blood pressure.
- A stomach ulcer.
- A history of having had surgery in the previous three months.
- A history of having had a stroke in the previous six months.
Inositol nicotinate – should not be given to people who have had a recent heart attack (myocardial infarction) or stroke.
Moxisylyte – is safe to use in most people.
Pentoxifylline – should not be given to people who have had:
- A stroke.
- Extensive back of the eye (retinal) bleeding.
- A heart attack.
- Heart rhythm problems.
For more detailed information, see the leaflet that comes with the medicine packet.
How to use the Yellow Card Scheme
If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at www.mhra.gov.uk/yellowcard.
The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:
- The side-effect.
- The name of the medicine which you think caused it.
- The person who had the side-effect.
- Your contact details as the reporter of the side-effect.
It is helpful if you have your medication – and/or the leaflet that came with it – with you while you fill out the report.
While taking nitrates, you should avoid smoking. Smoking can decrease the effect of the medicine. You should also avoid alcohol, because it can increase the effect of the medicine.
What else should I tell my doctor?
Talk to your doctor about your medical history before you start taking nitrates. The risks of taking the medicine need to be weighed against the good it will do. Here are some things to consider if you and your doctor are deciding whether you should take a nitrate.
- You are thinking of becoming pregnant, you are pregnant, or you are breast-feeding your baby.
- You are over 60. Dizziness is more common in older patients.
- You have recently had a stroke.
- You have recently had a heart attack.
- You have kidney or liver disease.
- You have an overactive thyroid.
- You often have severe headaches.
- You have anemia.
- You have glaucoma.
What are the side effects?
Sometimes a medicine causes unwanted effects. These are called side effects. Not all of the side effects for nitrates are listed here. If you feel these or any other effects, you should check with your doctor.
Common side effects:
- Flushing of your face and neck
- Upset stomach or throwing up
- Low blood pressure (hypotension)
- Irregular heart rhythms (arrhythmia)
Less common side effects:
Rare side effects:
- Dry mouth
- Skin rash and peeling
- Blurry vision
Again, tell your doctor right away if you have any of these side effects. Do not stop taking your medicine unless your doctor tells you to. If you stop taking your medicine without checking with your doctor, it can make your condition worse.
Vasodilators are medications used to open up blood vessels and prevent heart-related health conditions, but there are also natural vasodilators that can dilate vessels and increase blood flow.
Vasodilators impact the muscle walls of the arteries and veins. They prevent the muscles from tightening and the wall from narrowing, which then allow blood to flow more freely through vessels. When blood is flowing easily, the heart doesn’t have to work as hard and blood pressure is reduced.
The production of NO—nitric oxide—is important for the regulation of blood flow. Abnormal NO production occurs in different disease situations. It can have a negative impact on blood flow and vascular functions. Nitric oxide is produced from the amino acid L-arginine by action from nitric oxide synthase (NOS). Vascular actions of NO can include preventing sympathetic vasoconstriction, acting as an anti-inflammatory, having an anti-thrombotic effect, and preventing muscle hyperplasia. On the other hand, when NO production is hampered, it can lead to hypertension, thrombosis, vascular hypertrophy and stenosis, or excess inflammation.
Nitric oxide is a strong vasodilator; something you can get from flavonoid and L-arginine rich foods. There are many natural vasodilator foods to choose from. Read on for a comprehensive list of some of the best natural vasodilator food options.
Natural vasodilators to increase blood flow
Nitric oxide can reduce blood pressure as well as prevent artery blockage and stroke. Boosting nitric oxide levels with food is sometimes a preferred option. No matter what your taste buds are like, you are bound to find something on the following list of natural vasodilators that you can enjoy.
Raw cacao bean increases nitric oxide and is also full of antioxidants. It can lower blood pressure and impact markers of inflammation. Keep in mind that it is loaded with sugar, so it should be consumed occasionally. Remember that we are referring to dark chocolate only.
Related: How to lower blood pressure quickly and naturally
Research suggests that vitamin C protects nitric oxide molecules from free radical damage, making it a good natural vasodilator. Foods like oranges, lemons, and grapefruit contain large amounts of vitamin C. This vitamin is known to raise levels of nitric oxide synthase, which again is the enzyme that converts L-arginine into nitric oxide.
This fruit is capable of boosting nitric oxide, reducing inflammation, and reducing oxidative stress, which are all factors related to coronary artery disease. Polyphenols in pomegranate help convert nitrite into nitric oxide, making it a viable natural vasodilator.
This nut is high in L-arginine, so it can keep blood vessels open. Many other nuts are also good sources of L-arginine. Nutritionists suggest soaking nuts for five to six hours before consuming them. If you don’t like walnuts, you can consider almonds, cashews, pine nuts, Brazil nuts, or macadamia nuts.
This type of lettuce has the highest source of nitrates. It can be a little bitter, so many people mix it in with other types of lettuce or sauté it with other vegetables. Arugula is also called garden rocket or salad rocket. It is often referred to in England as a “fancy pants” (more sophisticated) kind of leaf lettuce.
In its fresh form (not canned), this leafy vegetable is packed with nitrates. This versatile veggie can be added to soups, stews, pasta dishes, or even pizza.
A number of studies call beetroot an excellent vasodilator, especially when it comes to lowering blood pressure. Beets are also a source of anti-oxidants and betalains, which are good anti-inflammatories.
While this does not contain a lot of nitrates, it does boost the enzyme nitric oxide synthase. Research indicates that garlic supplements can lower blood pressure and have many other health benefits. Garlic is a very popular vegetable among many different cultures and can be used in countless dishes.
This popular herb, which is also found in many different supplements, is a natural vasodilator. The great thing about parsley is that it also contains other properties that promote good health. Since parsley does not have a strong flavor, it is used often in restaurants.
The ginger root is known as a vasodilator. It can open up blood vessels to allow blood to pass through. It also has anti-inflammatory properties. The root of the ginger can be consumed fresh, powdered, dry as a spice, in oil form, or as a juice. There are many other health benefits linked to ginger root besides the fact that it can act like a vasodilator.
This spice has a warming impact, which can help dilate blood vessels. Using excessive amounts of cayenne is not recommended, but including a little in meals can be helpful.
Fresh rosemary can increase blood flow and is a great food additive. Poultry and lamb are good examples of foods that many people sprinkle with rosemary.
This amino acid can be found in protein-rich foods, such as chicken, turkey, and dairy products. Arginine is a precursor to nitric oxide, so it is one of the best natural vasodilator options.
This has been used for centuries to address blood circulation problems and heart issues. It can interact with other heart medications, so it is important to use Hawthorne under the supervision of a qualified healthcare professional.
Research has shown that coffee can boost vasodilation and blood flow. One study conducted in 2015 showed that men are less likely to experience erectile dysfunction due to poor blood flow when they drink two or more cups of coffee each day.
When it comes to the best natural vasodilator options, it is nice to see that there are a wide variety of foods to choose from. While this should bring some reassurance, especially to those who are not keen on vasodilator medications, any use of foods to control vascular health should be discussed with a doctor. Taking treatment into your own hands can be dangerous. When planned in consultation with a healthcare professional though, foods can make a big difference when it comes to vasodilation.
19 foods that increase blood flow
Essential oils for circulation: 10 best oils to improve blood circulation
Tweet this: Dietary changes, lifestyle strategies, and supplements have the potential to reverse high blood pressure without the need for a lifelong prescription.
Nutrients for Lowering Blood Pressure
Hypertension affects 33 percent of American adults, yet only 1 percent of hunter–gatherer populations following a traditional diet develop high blood pressure (5). The Standard American Diet, full of added sugars, refined grains, and industrial seed oils, sets the stage for hypertension to develop. The following nutrients and food guidelines, as part of a Paleo diet, can help lower blood pressure.
Excess sugar intake increases blood pressure, and reducing added sugars lowers blood pressure (5, 6, 7). Added sugars can lurk in surprising foods, including salad dressings, canned beans, and bacon.
High potassium intake is associated with lower blood pressure (8, 9, 10). The average American only consumes 2,800 mg per day, far below the recommended 4,700 mg (11). Paleo diets, on the other hand, average 10,500 mg per day. Starchy vegetables and tubers are terrific sources.
Increasing serum measurements of DHA/EPA, markers of fish intake, are related to lower blood pressure (12, 13, 14). However, steer clear of most fish oil supplements and instead have patients obtain beneficial nutrients from whole foods whenever possible. A recent analysis showed that the three top-selling fish oils in the United States contained oxidized lipids that may be causing more harm than good (15). Beyond DHA and EPA, fish also have selenium, zinc, iron, and a highly absorbable protein that also may reduce blood pressure (16). Aim for cold-water fatty fish three times a week.
High magnesium intake is associated with lower blood pressure and may have a synergistic effect with potassium. Increasing both nutrients while moderately reducing sodium can lower blood pressure to the same extent as a single medication (17). Magnesium stimulates vasodilators and can inhibit free radical formation in blood vessels (18). Nuts, seeds, spinach, beet greens, and chocolate are good whole food sources.
Adequate vitamin K2 helps keep calcium from residing in blood vessels, thereby preventing hypertension and calcification (19). Vitamins K1 and K2 have different forms and functions. Vitamin K1 is abundant in leafy greens and many other foods, while vitamin K2 sources are more uncommon: natto (fermented soy), some cheeses, butter from grass-fed cows, goose liver, and egg yolks.
Vitamin D deficiency is associated with increased risk of developing hypertension (20), and large doses of vitamin D (50,000 IU per week) have been shown to lower blood pressure over eight weeks (21). One mechanism by which vitamin D may lower blood pressure is through suppressing renin, which regulates mean arterial blood pressure (22). Sun exposure is an easy and cheap way to get vitamin D.
Despite what mainstream medicine claims, restricting salt too much can actually increase the risk of death from CVD (23). Unless your patient is part of the small minority of salt-sensitive people, there is no reason to advise consuming less than 1.5 teaspoons, or 3,600 mg, per day, which is the average American consumption.
Lifestyle Changes Are Safe, Effective, and Underutilized
What we eat is only part of the picture of good health. Lifestyle choices carry equal weight, yet they are often only considered as afterthoughts. Take some time to seriously discuss with patients what changes need to be made.
Over one-third of U.S. adults are now obese. It’s no secret that gaining weight increases blood pressure, and losing weight in a healthy manner lowers blood pressure (35, 36, 37).
Some patients will cringe at the suggestion of exercise, because they envision a chronic cardio scenario like a mouse on a running wheel. Spread the good news: exercise of all kinds—endurance, dynamic resistance, HIIT, isometric resistance—has the potential to reduce blood pressure (38). Whatever exercise your patients will actually do on a regular basis is the best recipe for success. In patients with extreme hypertension, be cautious with exercises that may further increase blood pressure to an unsafe zone (39).
Short and poor-quality sleep are both associated with raised blood pressure (40). On the other side of the spectrum, excessively long sleep may also be harmful. One study found increased blood pressure in those who got fewer than five hours of sleep per night and in those who averaged more than nine hours of sleep per night, when compared with people who slept around seven hours (41). I suspect that it’s not the long sleep itself that is the problem, but that some underlying condition is both increasing sleep requirement and raising blood pressure.
Sunlight exposure increases the vasodilator nitric oxide and can lower blood pressure. UVB rays also help manufacture subcutaneous vitamin D3, a nutrient already discussed above (42).
Meditation of all types is associated with blood pressure control, enhanced insulin resistance, and reduced lipid peroxidation (43). Its relaxing effects on the nervous system are effective in both young and older adults (44, 45).
I have several articles about the importance of stress management, as stress is a major risk factor for high blood pressure and CVD (46). Self-care, proper sleep, and letting go of “busyness” are several strategies.
Knowing what changes to make is only the first step; following through in sustainable, practical ways is the tougher aspect of healthy living. This is where health coaching, one of the fastest-growing professional fields, can make all the difference. Many patients know what diet and lifestyle changes are needed, but they have trouble following through day to day. A health coach can provide the more frequent support and accountability that a general healthcare provider cannot.
Supplements for Lowering Blood Pressure
Below are supplements I recommend for lowering blood pressure. However, prescription medications should be considered if diet and lifestyle aren’t adequate or if blood pressure has been high for a while because high blood pressure is such a significant risk factor for CVD and death.
CoQ10 is an antioxidant that has vasodilation effects (53). Levels are generally lower in patients with high blood pressure, CVD, and type 2 diabetes. Newer formulas help improve absorption of this fat-soluble supplement.
Allicin, found in garlic, is a vasodilating agent and can reduce blood pressure (54, 55). Because heat during processing can lower the allicin content of supplements, not all products are equal. My preference is Garlicin.
Doses of 500 to 1,000 milligrams per day can have a small but significant effect on lowering blood pressure (56, 57). Chelated forms like magnesium glycinate are best absorbed.
Supplementing with 1,000 to 2,000 milligrams per day of potassium can be effective, especially when dietary potassium is inadequate, such as when a patient is on a low-carb diet and avoiding starchy foods like potatoes, sweet potatoes, plantains, and bananas (58).
Cod Liver Oil
If patients are not eating cold-water fatty fish a few times a week, one gram per day of cod liver oil may help.
Therapeutic Uses of Vasodilators
- Systemic and pulmonary hypertension
- Heart failure
As the name implies, vasodilator drugs relax the smooth muscle in blood vessels, which causes the vessels to dilate. Dilation of arterial (resistance) vessels leads to a reduction in systemic vascular resistance, which leads to a fall in arterial blood pressure. Dilation of venous (capacitance ) vessels decreases venous blood pressure.
Vasodilators are used to treat hypertension, heart failure and angina; however, some vasodilators are better suited than others for these indications. Some vasodilators that act primarily on resistance vessels (arterial dilators) are used for hypertension, and heart failure, and angina; however, reflex cardiac stimulation makes some arterial dilators unsuitable for angina. Venous dilators are very effective for angina, and sometimes used for heart failure, but are not used as primary therapy for hypertension. Most vasodilator drugs are mixed (or balanced) vasodilators in that they dilate both arteries and veins and therefore can have wide application in hypertension, heart failure and angina. Some vasodilators, because of their mechanism of action, also have other important actions that can in some cases enhance their therapeutic utility or provide some additional therapeutic benefit. For example, some calcium channel blockers not only dilate blood vessels, but also depress cardiac mechanical and electrical function, which can enhance their antihypertensive actions and confer additional therapeutic benefit such as blocking arrhythmias.
Arterial dilator drugs are commonly used to treat systemic and pulmonary hypertension, heart failure and angina. They reduce arterial pressure by decreasing systemic vascular resistance. This benefits patients in heart failure by reducing the afterload on the left ventricle, which enhances stroke volume and cardiac output and leads to secondary decreases in ventricular preload and venous pressures. Anginal patients benefit from arterial dilators because by reducing afterload on the heart, vasodilators decrease the oxygen demand of the heart, and thereby improve the oxygen supply/demand ratio. Oxygen demand is reduced because ventricular wall stress is reduced when aortic pressure is decreased. Some vasodilators can also reverse or prevent arterial vasospasm (transient contraction of arteries), which can precipitate anginal attacks.
Most drugs that dilate arteries also dilate veins; however, hydralazine, a direct acting vasodilator, is highly selective for arterial resistance vessels.
The effects of arterial dilators on overall cardiovascular function can be depicted graphically using cardiac and systemic vascular function curves as shown to the right. Selective arterial dilation decreases systemic vascular resistance, which increases the slope of the systemic vascular function curve (red line) without appreciably changing the x-intercept (mean circulatory filling pressure). This alone causes the operating point to shift from A to B, resulting in an increase in cardiac output (CO) with a small increase in right atrial pressure (PRA). The reason for the increase in PRA is that arterial dilation increases blood flow from the arterial vasculature into the venous vasculature, thereby increasing venous volume and pressure. However, arterial dilators also reduce afterload on the left ventricle and therefore unload the heart, which enhances the pumping ability of the heart. This causes the cardiac function curve to shift up and to the left (not shown in figure). Adding to this afterload effect is the influence of enhanced sympathetic stimulation due to a baroreceptor reflex in response to the fall in arterial pressure, which increases heart rate and inotropy. Because of these compensatory cardiac responses, arterial dilators increase cardiac output with little or no change in right atrial pressure (cardiac preload). Although cardiac output is increased, systemic vascular resistance is reduced relatively more causing arterial pressure to fall. The effect of reducing afterload on enhancing cardiac output is even greater in failing hearts because stroke volume more sensitive to the influence of elevated afterload in hearts with impaired contractility.
Drugs that dilate venous capacitance vessels serve two primary functions in treating cardiovascular disorders:
- Venous dilators reduce venous pressure, which reduces preload on the heart thereby decreasing cardiac output. This is useful in angina because it decreases the oxygen demand of the heart and thereby increases the oxygen supply/demand ratio. Oxygen demand is reduced because decreasing preload leads to a reduction in ventricular wall stress by decreasing the size of the heart.
- Reducing venous pressure decreases proximal capillary hydrostatic pressure, which reduces capillary fluid filtration and edema formation. Therefore, venous dilators are sometimes used in the treatment of heart failure along with other drugs because they help to reduce pulmonary and/or systemic edema that results from the heart failure.
Although most vasodilator drugs dilate veins as well as arteries, some drugs, such as organic nitrate dilators are relatively selective for veins.
The effects of selective venous dilators on overall cardiovascular function in normal subjects can be depicted graphically using cardiac and systemic vascular function curves as shown to the right. Venous dilation increases venous compliance by relaxing the venous smooth muscle. Increased compliance causes a parallel shift to the left of the vascular function curve (red line), which decreases the mean circulatory filling pressure (x-intercept). This causes the operating point to shift from A to B, resulting in a decrease in cardiac output (CO) with a small decrease in right atrial pressure (PRA). The reason for these changes is that venous dilation, by reducing PRA, decreases right ventricular preload, which decreases stroke volume and cardiac output by the Frank-Starling mechanism. Although not shown in this figure, reduced cardiac output causes a fall in arterial pressure, which reduces afterload on the left ventricle and leads to baroreceptor reflex responses, both of which can shift the cardiac function curve up and to the left. Sympathetic activation can also lead to an increase in systemic vascular resistance. The cardiac effects (decreased cardiac output) of venous dilation are more pronounce in normal hearts than in failing hearts because of where the hearts are operating on their Frank-Starling curves (cardiac function) curves ( for more information).
Therefore, the cardiac and vascular responses to venous dilation are complex when both direct effects and indirect compensatory responses are taken into consideration. The most important effects in terms of clinical utility for patients are summarized below.
Venous dilators reduce:
- Venous pressure and therefore cardiac preload
- Cardiac output
- Arterial pressure
- Myocardial oxygen demand
- Capillary fluid filtration and tissue edema
Mixed or “balanced” dilators
As indicated above, most vasodilators act on both arteries and veins, and therefore are termed mixed or balanced dilators. Notable exceptions are hydralazine (arterial dilator) and organic nitrate dilators (venous dilators).
The effects of mixed dilators on cardiac and systemic vascular function curves are shown in the figure to the right. The red line represents a systemic function curve generated when there is both venous dilation (increased venous compliance) and arterial dilation (reduced systemic vascular resistance) – the mean circulatory filling pressure (x-axis) is decreased and the slope is increased. Point B represents the new operating point, although it is important to note that where this point lies depends on the relative degree of venous and arterial dilation. If there is more arterial dilation than venous dilation, then point B may be located slightly above point A where the cardiac function curve intersects with the new vascular function curve.
To summarize the effects of mixed vasodilators, we can say that in general they decrease systemic vascular resistance and arterial pressure with relatively little change in right atrial (or central venous) pressure (i.e., little change in cardiac preload), and they have a relatively little effect on cardiac output.
Side-Effects of Vasodilators
There are three potential drawbacks in the use of vasodilators:
- Systemic vasodilation and arterial pressure reduction can lead to a baroreceptor-mediated reflex stimulation of the heart (increased heart rate and inotropy). This increases oxygen demand, which is undesirable if the patient also has coronary artery disease.
- Vasodilators can impair normal baroreceptor-mediated reflex vasoconstriction when a person stands up, which can lead to orthostatic hypotension and syncope upon standing.
- Vasodilators can lead to renal retention of sodium and water, which increases blood volume and cardiac output and thereby compensates for the reduced systemic vascular resistance.
Drug Classes and General Mechanisms of Action
Vasodilator drugs can be classified based on their site of action (arterial versus venous) or by mechanism of action. Some drugs primarily dilate resistance vessels (arterial dilators; e.g., hydralazine), while others primarily affect venous capacitance vessels (venous dilators; e.g., nitroglycerine). Most vasodilator drugs, however, have mixed arterial and venous dilator properties (mixed dilators; e.g., alpha-adrenoceptor antagonists, angiotensin converting enzyme inhibitors).
It is more common, however, to classify vasodilator drugs based on their primary mechanism of action. The figure to the right depicts important mechanistic classes of vasodilator drugs. These classes of drugs, as well as other classes that produce vasodilation, are listed below. (Click on the drug class for more details)
- Alpha-adrenoceptor antagonists (alpha-blockers)
- Angiotensin converting enzyme (ACE) inhibitors
- Angiotensin receptor blockers (ARBs)
- Beta2-adrenoceptor agonists (β2-agonists)
- Calcium-channel blockers (CCBs)
- Centrally acting sympatholytics
- Direct acting vasodilators
- Endothelin receptor antagonists
- Ganglionic blockers
- Phosphodiesterase inhibitors
- Potassium-channel openers
- Renin inhibitors
Note that many of the drugs in the above mechanistic classes have actions other than vasodilation, and therefore are classified additionally under other mechanistic classes. For example, dobutamine possesses non-selective beta-adrenoceptor agonist properties and therefore produces both vasodilation and cardiac stimulation. It also has alpha-adrenoceptor agonist properties that can cause vasoconstriction at high plasma concentrations.
High Blood Pressure Medicines
Blood pressure is the amount of force that your blood puts on your artery walls as it moves through your body. High blood pressure (also called hypertension) occurs when your blood moves through your arteries at a higher pressure than normal. Many different things can cause high blood pressure. If your blood pressure gets too high or stays high for a long time, it can cause health problems. That is why it is important to treat high blood pressure. Medicines are one of the most common methods of treatment.
Path to improved health
There are many types of medicine used to treat high blood pressure. Your doctor will decide which type of medicine is right for you. These are the most common.
- ACE inhibitors (angiotensin-converting enzyme inhibitors) – keep your body from making hormone angiotensin II. The hormone causes blood vessels to narrow. This relaxes your blood vessels and opens them up.
- Alpha blockers – help relax your blood vessels by reducing nerve impulses. This allows your blood to pass through more easily.
- Angiotensin II receptor blockers (ARBs) – blocks the effects of hormone angiotensin II. The hormone causes blood vessels to narrow. This allows your blood vessels to stay open.
- Beta blockers – make the heart beat slower so that blood passes through your blood vessels with less force.
- Calcium channel blockers (CCBs) – prevent calcium from entering the cells of your heart and arteries. This helps keep your blood vessels from contracting with extra force.
- Central agonists – reduce the nerve impulses that cause the blood vessels to tense up or contract. They work the same way as alpha and beta blockers, but they follow a different nerve pathway.
- Diuretics (water pills) – help your body get rid of extra sodium (salt) and water. This reduces the amount of fluid flowing through your blood vessels and lowers your blood pressure.
- Vasodilators (blood vessel dilators) – relax the muscles in the blood vessel walls. This causes the blood vessels to widen (dilate) so blood can flow through better.
Things to consider
All medicines can have side effects. Some possible side effects of high blood pressure medicines include:
- chest pain, heart palpitations (the feeling that your heart is racing) or arrhythmia (irregular heartbeat)
- cough, fever, congestion, upper respiratory tract infection, or flu-like symptoms
- diarrhea or constipation
- dizziness or lightheadedness
- nervousness or anxiety
- problems with erections and sexual function
- skin rash
- tiredness, weakness, drowsiness or lethargy (lack of energy)
- unintended weight loss or gain
Tell your doctor as soon as possible if your side effects become severe or bothersome.
What about medicine interactions?
If you use 2 or more medicines at the same time, the way your body processes each one can change. When this happens, the risk of side effects from each medicine increases. Each medicine may not work the way it should. Be sure your doctor knows all of the medicines you are taking. These include over-the-counter and prescription medicines, vitamins, and herbal supplements.
Also ask your doctor whether you need to avoid any foods or drinks while using your blood pressure medicine. For example, people taking certain CCBs may need to avoid eating grapefruit or drinking grapefruit juice.
Questions to ask your doctor
- What type of blood pressure medicine is best for me?
- How does this medicine work?
- What are the side effects of this medicine?
- How long will I need to take this medicine?
- Are there any lifestyle changes I can make to lower my blood pressure?
U.S. National Library of Medicine, Blood Pressure Medicines
American Heart Association, What You Should Know About High Blood Pressure and Medications