People with pulmonary hypertension (PH) experience a narrowing of the vessels carrying blood from the heart to the lungs. Sometimes, doctors prescribe sildenafil under the brand name Revatio to treat PH.

Sildenafil is a phosphodiesterase inhibitor, which means that it stops the activity of the enzyme phosphodiesterase. This enzyme breaks down substances called cAMP and cGMP, so blocking its activity increases their levels. The increased levels of cAMP and cGMP, which regulate cell function, have various effects on the body, such as decreasing calcium levels, widening blood vessels, and relaxing muscles.

Sildenafil may be better known as a treatment of erectile dysfunction, for which it is available under the brand name Viagra. However, it can also be an effective treatment for PH. Sildenafil for this purpose is called Revatio.

This article explains how doctors use sildenafil to treat pulmonary hypertension. It also looks at the side effects of the medication, the precautions people must take when using it, and when to contact a doctor.

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When people have pulmonary hypertension, their pulmonary arteries — the large blood vessels between the heart and lungs — are tight and narrow. People use sildenafil for pulmonary hypertension because it widens these arteries, allowing the blood to flow more easily to the lungs. It also reduces blood pressure.

In a 2017 clinical trial that features in BMC Pulmonary Medicine, researchers randomly assigned 129 people with pulmonary arterial hypertension to one of three groups. They prescribed 1 milligram (mg), 5 mg, and 20 mg of sildenafil to each group, telling them to take it three times daily.

After the first 12 weeks of the trial, the average distance that people could walk in 6 minutes increased significantly in the group taking 20 mg of sildenafil compared with the group taking 1 mg. At the end of the full 24-week period, those in the 20-mg group showed the largest increase in their 6-minute walking distance.

This research indicates that sildenafil increases cardiovascular abilities and endurance, which can improve a person’s quality of life.

For adults with PH, the Food and Drug Administration (FDA) recommends taking 20 mg of sildenafil three times per day. People taking the medication should leave 4–6 hours between doses.

The sildenafil medication label explains that according to clinical trials, doses higher than 20 mg do not result in better effects. However, if a person does not respond to the medication, a doctor may increase their dose to a maximum of 80 mg three times per day.

As overall health and the severity of PA will vary among individuals, a person should follow the advice of a doctor and take their prescribed dosage.

The FDA does not recommend sildenafil for the treatment of PH in children aged 1–17 years.

Most people can take sildenafil for PH without any issues. However, as with all medications, it can cause side effects. These may include:

Many of these side effects will resolve on their own, and they are not necessarily an immediate cause for concern. If any of the above side effects are severe or persistent, a person should contact a doctor.

However, it is essential to seek medical care right away if any of the following side effects occur:

People taking sildenafil for PH should be aware of possible drug interactions. Certain individuals, such as those who are pregnant, should also avoid taking sildenafil.

Drug interactions

Certain foods, supplements, and other medications can all cause dangerous interactions.

For example, it is important to avoid taking sildenafil while taking nitrates or nitric oxide donors because these combinations can result in a dangerous drop in blood pressure. People should also exercise caution when consuming alcohol or blood pressure-lowering medications.

The liver enzyme CYP3A4 is responsible for breaking down sildenafil once it enters the body. Therefore, it is important to check whether any medications that a person is taking also affect this pathway. If someone is not sure whether a medication can cause this interaction, they should contact a doctor.

Bosentan (Tracleer) and epoprostenol (Flolan) are two drugs that people commonly use to treat PAH. However, if a person takes one of these medications at the same time as sildenafil, their blood levels of sildenafil may decrease. Conversely, taking beta-blockers — another type of heart and blood pressure medication — may increase a person’s blood levels of sildenafil.

Sildenafil may interact with certain HIV medications. A doctor can advise a person on whether they can take it safely.


Doctors do not recommend taking sildenafil while pregnant. If a person with PH who is taking the medication becomes pregnant, they should contact a doctor right away.

Low blood pressure

The United Kingdom’s National Institute for Health and Care Excellence (NICE) recommends that people with blood pressure below 90 millimeters of mercury avoid taking sildenafil.

The NICE also advises against taking the medication if a person has intravascular volume depletion, which is reduced blood volume in the blood vessels, or pulmonary veno-occlusive disease, which is obstruction of the vessels carrying oxygen-rich blood from the lungs to the heart.

It is important to speak with a doctor before taking sildenafil for PH. The doctor can use the latest guidelines to determine the appropriate dosage for a person based on their individual case and health.

A doctor can also advise a person on avoiding harmful drug interactions. They might recommend avoiding grapefruit and grapefruit juice or the herbal supplement St. John’s wort, which may interact with medications such as sildenafil.

Once a person has started taking sildenafil, it is important that they let the prescribing doctor know about any side effects they experience. The doctor can adjust the dosage accordingly.

Sildenafil — more commonly known as Viagra — can help treat pulmonary hypertension. It works by enlarging the blood vessels, allowing the blood to flow more easily to the lungs.

If a doctor thinks that sildenafil is a safe treatment for a person with PH, they will prescribe the appropriate dosage. Anyone who experiences any severe or persistent side effects should make the doctor aware.