Generic Name: sildenafil (sil-DEN-a-fil)
Medically reviewed by Drugs.com. Last updated on June 10, 2020.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Vasodilator
Pharmacologic Class: Phosphodiesterase Type 5 Inhibitor
Uses for sildenafil
Sildenafil injection is used to treat the symptoms of pulmonary arterial hypertension. This is a type of high blood pressure that occurs between the heart and the lungs. When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs.
Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. It works on the PDE5 enzyme in the lungs to relax the blood vessels. This will increase the supply of blood to the lungs and reduce the workload of the heart.
Sildenafil is available only with your doctor's prescription.
Before using sildenafil
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For sildenafil, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to sildenafil or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Sildenafil should not be used for pulmonary arterial hypertension in children, especially for chronic use.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of sildenafil injection in the elderly. However, elderly patients are more likely to have age-related liver, kidney, or heart problems, which may require caution and an adjustment in the dose for patients receiving sildenafil injection.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are receiving sildenafil, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using sildenafil with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Amyl Nitrite
- Erythrityl Tetranitrate
- Isosorbide Dinitrate
- Isosorbide Mononitrate
- Pentaerythritol Tetranitrate
- Propatyl Nitrate
Using sildenafil with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Using sildenafil with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using sildenafil with any of the following may cause an increased risk of certain side effects but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use sildenafil, or give you special instructions about the use of food, alcohol, or tobacco.
- Grapefruit Juice
Other medical problems
The presence of other medical problems may affect the use of sildenafil. Make sure you tell your doctor if you have any other medical problems, especially:
- Abnormal penis, including a curved penis or birth defects of the penis—Chance of problems occurring may be increased and sildenafil should be used with caution in these patients.
- Angina (chest pain) or
- Arrhythmia (irregular heartbeat) or
- Heart attack or
- Heart disease or
- Hypertension (high blood pressure) or
- Hypotension (low blood pressure) or
- Priapism, history of or
- Retinitis pigmentosa (an inherited eye disorder) or
- Stroke—Use with caution. May cause side effects to become worse.
- Age greater than 50 years or
- Coronary artery disease or
- Crowded disc or low cup to disc ratio in the eye (an eye disorder) or
- Diabetes or
- Heart disease or
- Hyperlipidemia (high fats in the blood) or
- Hypertension (high blood pressure) or
- Non-arteritic anterior ischemic optic neuropathy or NAION (serious eye condition), history of or
- Smoking—May increase the chance for a serious side effect in the eye called NAION.
- Bleeding disorders, history of or
- Stomach ulcer, or history of or—Chance of problems occurring may be increased; it is not known if the medicine is safe for use in these patients.
- Leukemia (blood related cancer) or
- Multiple myeloma (blood related cancer) or
- Sickle-cell anemia (blood disorder)—Sildenafil should be used with caution in these patients as problems with prolonged erection of the penis may occur.
- Pulmonary veno-occlusive disease or PVOD (a type of lung disease)—May make this condition worse.
Proper use of sildenafil
A nurse or other trained health professional will give you sildenafil in a hospital. Sildenafil is given through a needle placed in one of your veins.
Your doctor will give you a few doses of sildenafil until your condition improves, and then switch you to an oral medicine that works the same way. If you have any concerns about this, talk to your doctor.
Precautions while using sildenafil
It is very important that your doctor check your progress while you are receiving sildenafil. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
Do not take Viagra® or other PDE5 inhibitors, such as tadalafil (Cialis®) or vardenafil (Levitra®). Viagra® also contains sildenafil. If you take too much sildenafil or take it together with these medicines, the chance for side effects will be higher.
Do not use sildenafil if you are also using a nitrate medicine for chest pain (angina). Some examples of nitrate medicines are: isosorbide, nitroglycerin, Imdur®, Nitro-Bid®, Nitro-Dur®, Nitrol® ointment, Nitrolingual® spray, Nitrostat®, and Transderm Nitro®. Some illegal ("street") drugs or "poppers" also contain nitrates, such as amyl nitrate, butyl nitrate, or nitrite. Do not use sildenafil if you also use riociguat (Adempas®).
It is important to tell your doctor about any heart problems you have now or may have had in the past. Sildenafil can cause serious side effects in patients with heart problems.
Sildenafil injection could make your blood pressure go too low. Tell your doctor right away if you have more than one of these symptoms: blurred vision, confusion, dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position, sweating, or unusual tiredness or weakness.
If you experience a sudden loss of vision in one or both eyes, contact your doctor right away.
Check with your doctor right away if you have a sudden decrease in hearing or loss of hearing, which may be accompanied by dizziness and ringing in the ears.
If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. This condition may require prompt medical treatment to prevent serious and permanent damage to your penis.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Sildenafil side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor or nurse immediately if any of the following side effects occur:
- Bloating or swelling of the face, arms, hands, lower legs, or feet
- bloody nose
- difficult or labored breathing
- rapid weight gain
- shortness of breath
- tightness in the chest
- tingling of the hands or feet
- unusual weight gain or loss
- Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
Incidence not known
- blurred vision
- decreased hearing
- decreased vision
- loss of hearing
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Acid or sour stomach
- difficulty with moving
- feeling of warmth
- flushing or redness of the skin
- joint pain
- muscle aching or cramping
- muscle pains or stiffness
- pain in the arms or legs
- redness of the face, neck, arms, and occasionally, upper chest
- stomach discomfort, upset, or pain
- swollen joints
- trouble sleeping
- unable to sleep
- unusually warm skin
- Burning feeling in the chest or stomach
- pain or tenderness around the eyes and cheekbones
- runny nose
- stuffy or runny nose
- tenderness in the stomach area
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Frequently Asked Questions
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