Sildenafil is best known as the little blue pill sold under the name Viagra. Under a different brand name, Revatio, the same active ingredient is used to treat pulmonary arterial hypertension (PAH), a rare and serious disease of the lung arteries. Its use in children has a complicated history: a large trial, an FDA warning, a later clarification and finally, in 2023, FDA approval for children aged 1 to 17. This article explains the disease, how sildenafil works, what the studies showed and what families should know. It does not replace advice from the child’s pulmonary hypertension team.
What Pulmonary Arterial Hypertension Is
In PAH, the small arteries in the lungs become narrow, thick and stiff. Blood pressure in the lung circulation rises, and the right side of the heart, which pumps blood into the lungs, has to work much harder. Over time the right ventricle can enlarge and weaken, leading to right heart failure. PAH is progressive and there is no cure, but treatment has improved survival and quality of life considerably.
In children, PAH is rare. It is diagnosed with an echocardiogram and confirmed by right heart catheterization, which measures the pressure in the lung arteries directly.
Symptoms in Children
- shortness of breath during play or exercise, later even at rest
- tiring much faster than other children
- fainting or near-fainting, especially during activity
- chest pain or a racing heartbeat
- bluish lips or skin (cyanosis)
- in babies: poor feeding, sweating while feeding, slow weight gain and fast breathing
- in advanced disease: swelling of the legs or belly
Because these signs are common to many conditions, PAH in children is often diagnosed late. Fainting during exercise always needs prompt medical evaluation.
Causes
- Idiopathic PAH: no cause can be found.
- Heritable PAH: caused by gene changes, most often in the BMPR2 gene; other family members may be at risk.
- Congenital heart disease: defects with extra blood flow to the lungs, such as large holes between the heart chambers, can damage the lung arteries if not repaired in time.
- Lung disease of prematurity: babies born very early with bronchopulmonary dysplasia have an increased risk.
- Other associations: Down syndrome, certain liver and connective tissue diseases, and some drugs and toxins.
How Sildenafil Works
Sildenafil belongs to the phosphodiesterase type 5 (PDE5) inhibitors. PDE5 breaks down a messenger molecule, cyclic GMP, that relaxes the muscle in blood vessel walls. By blocking PDE5, sildenafil lets the vessels widen. The lungs contain a lot of PDE5, so the drug lowers pressure in the lung arteries and eases the work of the right heart.
Pfizer launched sildenafil as Viagra for erectile dysfunction in 1998. In 2005 the FDA approved it as Revatio for adults with PAH, at lower and more frequent doses. Generic versions have been available since 2012, along with a liquid form that makes dosing in small children easier.
The Pediatric Studies
STARTS-1
After the FDA asked Pfizer to study sildenafil in children, the company ran the STARTS-1 trial, led by pediatric cardiologist Robyn Barst of Columbia University and published in the journal Circulation in 2012. It enrolled about 235 children aged 1 to 17 with PAH at centers in many countries. They received low, medium or high doses based on body weight, or a placebo, for 16 weeks. The primary measure, a change in peak oxygen use during exercise, narrowly missed statistical significance for all doses combined, while the medium and high doses showed improvements in exercise capacity and lung blood pressure.
STARTS-2
In the long-term extension study, children who stayed on the high dose had a higher death rate over several years than those on the low dose. This finding shaped the regulatory history.
From FDA Warning to Approval
- 2012: Based on STARTS-2, the FDA issued a safety communication recommending that Revatio not be prescribed to children with PAH.
- 2014: The FDA clarified that this was not a contraindication. Doctors could still use sildenafil in children when they judged the benefits to outweigh the risks, and many pediatric specialists continued to do so.
- 2023: After reviewing additional data, including an adult study that did not confirm the higher death rate with higher doses, the FDA approved Revatio for children aged 1 to 17 with PAH. The label sets weight-based doses and warns that higher doses than recommended should not be used.
Dosing must always be set and adjusted by the treating specialist. Families should never change the dose or switch between tablet and liquid forms without talking to the team.
Side Effects and Precautions
Common side effects include headache, flushing, nosebleeds, stuffy nose, upset stomach and diarrhea. Less common but important are vision or hearing changes, low blood pressure and, in boys, prolonged painful erections (priapism), which require emergency care. Sildenafil must not be combined with nitrate medicines or riociguat, because blood pressure can drop dangerously. Many other drugs interact with it, so every new prescription should be checked by a pharmacist.
Other Treatments and Specialized Care
Sildenafil is one of several options. Children with PAH may also receive:
- Endothelin receptor antagonists such as bosentan, which the FDA has approved for children aged 3 and older.
- Prostacyclin therapies such as epoprostenol or treprostinil, given by continuous infusion, injection or inhalation in more severe disease.
- Supportive care: oxygen, diuretics, vaccinations against flu and RSV, and careful planning around anesthesia and travel to high altitude.
- Combination therapy is increasingly common, using drugs that act on different pathways.
Because the disease is rare, children do best when cared for at a center with a dedicated pediatric pulmonary hypertension program. Many US centers work together in the Pediatric Pulmonary Hypertension Network. The National Heart, Lung, and Blood Institute (NHLBI) at the NIH provides reliable background information for families.
Frequently Asked Questions
Is Revatio the same drug as Viagra?
Both contain sildenafil, but Revatio is approved for pulmonary arterial hypertension and is used at different, lower doses taken several times a day.
Is sildenafil approved for children?
Yes. Since 2023, the FDA has approved Revatio for children aged 1 to 17 with PAH, with weight-based doses set by the treating physician.
Why did the FDA warn against it in 2012?
A long-term extension study found a higher death rate in children taking high doses. The FDA later clarified that doctors may weigh benefits and risks, and the 2023 approval limits use to recommended doses.
Can sildenafil cure pulmonary hypertension?
No. There is currently no cure for PAH. Sildenafil can improve exercise ability and lower pressure in the lung arteries as part of long-term treatment by a specialized team.
