Sildenafil belongs to a class of medications known as phosphodiesterase 5 inhibitors. Phosphodiesterase is an enzyme produced in the lungs and other parts of the body. This enzyme breaks down a substance called cyclic guanosine monophosphate.

Sildenafil, by decreasing phosphodiesterase activity, increases cGMP levels. The increased cGMP levels relax arteries in the lungs and lower blood pressure. When arteries in the lungs relax, it’s easier for the right side of the heart to pump blood through the lungs.

Sildenafil is available in tablet or liquid form. Your child should take this medicine by mouth, three times daily (breakfast, lunch, dinner). The maximum recommended dose is 20 mg three times a day, but dosing is based on weight in children and can vary. Always discuss dosage with your child’s pulmonary hypertension provider.

Sildenafil is generally well tolerated. Common side effects include:

• Headache
• Flushing
• Dizziness
• Nasal congestion/stuffy nose
• Nose bleeds
• Stomach upset
• Diarrhea
• Low blood pressure. Although sildenafil can lower overall blood pressure, it generally isn’t an issue unless your child experiences dizziness, fainting or other concerning symptoms. If your child shows low blood pressure symptoms, notify their physician immediately.

Uncommon but urgent side effects include:

• Vision loss or changes
• Hearing loss or changes
• Painful or prolonged erection (greater than four hours)

Although allergies to sildenafil are possible, they aren’t likely. Any medication can cause side effects or sensitivities. Check with your doctor if your child develops a rash or throat tightening.

Regular blood work isn’t required for sildenafil.

Sildenafil is available by prescription only. A specialty pharmacy selected by your insurance will ship the medication to your home. Common specialty pharmacies for PAH medications include Accredo, Aetna, Alliance Rx Walgreens Prime, Axium, BriovaRx, Cigna, CVS specialty, Humana and Kaiser Permanente.

Insurance plans often require a special approval, called prior authorization, before your child can start this medication.

Sildenafil shouldn’t be taken with certain medications, especially medications that can lower systemic blood pressure, such as nitrates. Check with your pulmonary hypertension provider before your child starts any new medications while on sildenafil.

People with bleeding disorders, pulmonary veno-occlusive disease, pulmonary capillary hemangiomatosis, sickle cell disease and peptic ulcer disease shouldn’t take this medication. Discuss disease-related concerns with your physician because this list isn’t comprehensive.

People with PAH are advised to avoid pregnancy. Patients who become pregnant (or their parents/guardians), should notify their physician immediately. However, doctors may consider sildenafil for pregnant patients with PAH. While there are no well-controlled human studies, there is no current evidence that sildenafil causes harm to fetuses.