When the blood vessels from the heart to the lungs tighten up, causing high blood pressure, doctors call it pulmonary arterial hypertension (PAH). It’s like a traffic jam in the lungs. PAH is just one type of pulmonary hypertension (PH), a condition when the blood vessels in the lungs are narrower than usual, making it harder for blood to flow through.

The underlying causes of PAH are complex, but studies have shown that a molecule called prostacyclin is related to the condition. This article explains what you need to know about prostacyclin and PAH.

1. Prostacyclin Helps Your Blood Vessels Function

Also called prostaglandin I-2, prostacyclin is a naturally occurring chemical in the body. Injury or inflammation triggers the innermost layer of endothelial cells (blood vessels) throughout the body to make and release prostacyclin.

Prostacyclin travels from the inside layer to other parts of blood vessels, activating nearby receptors. This works similarly to putting a key into a lock. Once prostacyclin links to these receptors, it causes the following actions:

• Decrease in inflammation
• Decrease in blood clotting
• Vasodilation (relaxation of the smooth muscle of blood vessels)
• Antiproliferation (blocking of smooth muscle overgrowth)

Proliferation of smooth muscle happens when extra cells grow in the walls of the blood vessels. This can lead to hypertension (high blood pressure). Prostacyclin helps counteract this process.

2. People With PAH Have Less Prostacyclin in Their Bodies

People with PAH show lower amounts of prostacyclin circulating in their bodies. This finding has led researchers to conclude that an imbalance between prostacyclin and other molecules may lead to PAH.

Lower amounts of prostacyclin in the body cause the blood vessels in the lungs to narrow, leading to vascular disease (disease of the blood vessels) and the symptoms of PAH. Many PAH medications approved by the U.S. Food and Drug Administration (FDA) affect the prostacyclin pathway to help lessen symptoms and slow down the disease.​

Because people with PAH have lower amounts of prostacyclin circulating in their bodies, they don’t get the benefits of the chemical. Instead, they experience higher levels of inflammation, smooth muscle overgrowth of their blood vessels, blood clotting, and a narrowing of blood vessels.

3. Prostacyclin Medications Can Be Used To Treat PAH

Treatments for PAH include:

• Balloon atrial septostomy
• Calcium channel blockers
• Diuretics
• Pulmonary vasodilators
• Oxygen treatment

In cases of severe PH, a lung transplant may be necessary. All of these therapies work in different ways to improve blood flow and decrease pulmonary artery pressure.

Doctors sometimes prescribe a newer type of treatment for PAH called prostacyclin analogs (prostanoids). These medications help to counter prostacyclin imbalances by acting as stand-ins for the body’s prostacyclins.

Prostacyclin medications help to decrease inflammation, block smooth muscle overgrowth, limit blood clotting, and open blood vessels. They act the same as natural prostacyclin in the body.

Doctors usually recommend prostacyclin analogs for people with PAH who are in a higher-risk group, have more advanced PAH or who are not responding well to other therapies. It can be used for monotherapy (a stand-alone medication) or in combination therapy (multiple medications).​

Getting the dose right with prostacyclins can be difficult. Also, people on prostacyclins for PAH can develop a tolerance to the medication — along with unwanted side effects.

4. Prostacyclin Medications May Cause Side Effects

Like most pharmaceutical drugs, prostacyclin drugs are linked to the risk of side effects. They may include any of the following:

• Head or jaw pain
• Muscle aches and joint pain
• Nausea and vomiting
• Diarrhea
• Flushing
• Anemia (low levels of red blood cells)
• Reduced appetite
• Rash
• Overactive thyroid (for people taking selexipag)

In addition, injectable forms of prostacyclin drugs — such as subcutaneous treprostinil — can cause pain at the injection site.

Talk to your doctor about any effects you experience after starting or switching PAH medications. They can help you understand what’s normal and what’s a cause for concern. They can also explain whether side effects will diminish over time or if there are ways to lessen their severity.

Importantly, tell your doctor if worsening side effects are making it difficult for you to stick with your treatment.

5. The FDA Has Approved Two Types of Prostacyclin Therapy

Based on results from clinical trials, the U.S. Food and Drug Adminisration (FDA) has approved two types of prostacyclin therapy for treating PAH: prostacyclin analogs and prostacyclin IP receptor agonists.

Unlike prostacyclin analogs, a prostacyclin receptor agonist doesn’t try to copy the shape of the body’s own prostacyclin. However, a prostacyclin receptor agonist still acts like the body’s own prostacyclin and has a similar effect on the body as natural prostacyclin.

Prostacyclin analogs include:

• Epoprostenol, sold as Flolan and Veletri — Administered intravenously (through a vein)
• Iloprost, sold as Ventavis — Inhaled
• Treprostinil, sold as Tyvaso and Remodulin — Can be inhaled, taken orally, or given intravenously

The one FDA-approved prostacyclin IP receptor agonist is selexipag, sold as Uptravi. It’s available in tablet form.

People need careful dose monitoring and adjustments by their doctor when taking any of these medications.

Other Approved Medications for PAH Treatment

Other groups of medications for the treatment of PAH include endothelin receptor antagonists and phosphodiesterase-5 (PDE-5) inhibitors.

Examples of endothelin receptor antagonists include:

• Bosentan (Tracleer)
• Macitentan (Opsumit)
• Ambrisentan (Letairis)

Examples of PDE-5 inhibitors include sildenafil (Revatio) and tadalafil (Adcirca).

6. Resources Are Available To Make Prostacyclin Treatment More Affordable

Many treatments for PAH, including prostacyclin drugs, are expensive in the United States. The Pulmonary Hypertension Association recommends resources that can help people afford their medications. These resources include programs offered through drug manufacturers.

You can also ask your health care provider about resources to make medications more affordable.

Find Your Team

On myPHteam, the online social network for people with pulmonary hypertension and their loved ones, more than 53,000 members come together to ask questions, give advice, and share their stories.

Are you living with pulmonary arterial hypertension? Have you taken prostacyclin analogs for your symptoms? Share your experience in the comments below, or start a conversation by posting on your Activities page.