Sildenafil is used to treat high blood pressure in the lungs (pulmonary hypertension). It works by relaxing and widening the blood vessels in your lungs which allows the blood to flow more easily. Decreasing high blood pressure in the lungs allows your heart and lungs to work better and improves your ability to exercise.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

Sildenafil is also available in other brands and other strengths for erectile dysfunction-ED in men.

Read the Patient Information Leaflet if available from your pharmacist before you start taking sildenafil and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

To treat high blood pressure in the lungs, take this medication by mouth with or without food as directed by your doctor, usually 3 times a day. The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Children's dosage is also based on weight.

Do not increase your dose or take this drug more often than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.

Take this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Tell your doctor if your condition does not get better or if it gets worse.

Dizziness, lightheadedness, headache, flushing, stomach upset, nosebleeds, trouble sleeping, or swollen hands/ankles/feet (edema) may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Rarely, sudden decreased vision, or even permanent blindness, may occur in one or both eyes (NAION). If this serious problem occurs, stop taking sildenafil and get medical help right away. You have a slightly greater chance of developing NAION if you have heart disease, diabetes, high cholesterol, certain other eye problems ("crowded disk"), high blood pressure, if you are over 50, or if you smoke.

Rarely, a sudden decrease or loss of hearing, sometimes with ringing in the ears and dizziness, may occur. Stop taking sildenafil and get medical help right away if these effects occur.

Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur.

Get medical help right away if you have any very serious side effects, including:

• increased shortness of breath or trouble breathing
• fainting

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking sildenafil, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• heart problems (such as heart attack or life-threatening irregular heartbeat in the past 6 months, chest pain/angina, heart failure)
• stroke in the past 6 months
• high or low blood pressure
• dehydration
• penis conditions (such as angulation, fibrosis/scarring, Peyronie's disease)
• history of painful/prolonged erection (priapism)
• conditions that may increase the risk of priapism (such as sickle cell anemia, leukemia, multiple myeloma)
• eye problems (such as retinitis pigmentosa, sudden decreased vision, NAION)
• other lung conditions (such as pulmonary veno-occlusive disease)

This drug may make you dizzy or cause vision problems. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness or clear vision until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, sildenafil should be used only when clearly needed. Since high blood pressure in the lungs is a serious condition that can harm both a pregnant woman and her unborn baby, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, discuss with your doctor right away the benefits and risks of using this medication during pregnancy.

This medication passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are:

• riociguat
• vericiguat

Sildenafil can cause a serious drop in your blood pressure when used with nitrates. A serious drop in blood pressure can lead to dizziness, fainting, and rarely heart attack or stroke. Do not use sildenafil with any of the following:

• certain drugs used to treat chest pain/angina (nitrates such as nitroglycerin, isosorbide)
• recreational drugs called "poppers" containing amyl or butyl nitrite

If you are also taking an alpha blocker medication (such as doxazosin, tamsulosin) to treat an enlarged prostate/BPH or high blood pressure, your blood pressure may get too low which can lead to dizziness or fainting. Your doctor may adjust your medications to minimize your risk of low blood pressure.

Other medications can affect the removal of sildenafil from your body, which may affect how sildenafil works. Examples include azole antifungals (such as itraconazole, ketoconazole), cobicistat, macrolide antibiotics (such as clarithromycin, erythromycin), mifepristone, HIV protease inhibitors (such as atazanavir, darunavir), rifampin, ritonavir, among others.

Do not take this medication with any other product that contains sildenafil or other similar medications for erectile dysfunction-ED or pulmonary hypertension (such as tadalafil, vardenafil).

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, fainting, painful/prolonged erection.

Do not share this medication with others.

Lab and/or medical tests (such as eye exams, blood pressure) may be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.