Medically reviewed by Drugs.com. Last updated on Sep 1, 2021.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
- Powder for Suspension
Therapeutic Class: Erectile Dysfunction Agent
Pharmacologic Class: Phosphodiesterase Type 5 Inhibitor
Uses for sildenafil
Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where this enzyme works.
Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. When a man is sexually stimulated, his body's normal response is to increase blood flow to his penis to produce an erection. By controlling the enzyme, sildenafil helps to maintain an erection after the penis is stroked. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection.
Sildenafil is also used in both men and women 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 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 never be used in children for erectile dysfunction. In general, 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 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.
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 taking 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
- Pomelo 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 (severe chest pain), unstable or
- Arrhythmia (irregular heartbeat, within the last 6 months) or
- Blood vessel problems (eg, aortic stenosis, idiopathic subaortic stenosis) or
- Heart attack (within the last 6 months) or
- Heart failure or
- Hypertension (high blood pressure) or
- Hypotension (low blood pressure) or
- Retinal disorders (eye problem) or
- Retinitis pigmentosa (an inherited eye disorder) or
- Stroke (within the last 6 months)—Should not be used in patients with these conditions.
- 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.
- Kidney disease, severe or
- Liver disease, severe—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
- 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)—Use with caution. May make this condition worse.
Proper use of sildenafil
Use sildenafil exactly as directed by your doctor. Do not use more of it and do not use it more often than your doctor ordered. If too much is used, the chance of side effects is increased.
Special patient instructions comes with sildenafil. Read the directions carefully before you start using sildenafil and each time you get a refill of your medicine.
You may take sildenafil with or without food.
If you are using the oral liquid, shake the bottle well for at least 10 seconds before measuring each dose. Use the oral syringe provided in the package to measure each dose. Wash the oral syringe after each use.
Sildenafil usually begins to work for erectile dysfunction within 30 minutes after taking it. It continues to work for up to 4 hours, although its action is usually less after 2 hours.
Use only the brand of sildenafil that your doctor prescribed. Different brands may not work the same way.
The dose of sildenafil will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of sildenafil. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For treatment of erectile dysfunction:
- For oral dosage form (tablets):
- Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. Your doctor may adjust your dose if needed.
- Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. Your doctor may adjust your dose if needed.
- Children—Use is not recommended.
- For oral dosage form (tablets):
- For treatment of pulmonary arterial hypertension:
- For oral dosage forms (suspension or tablets):
- Adults—5 or 20 milligrams (mg) three times a day. Each dose should be taken about 4 to 6 hours apart.
- Children—Use and dose must be determined by your doctor.
- For oral dosage forms (suspension or tablets):
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Throw away any unused mixed Revatio® oral liquid after 60 days.
Precautions while using sildenafil
It is important that you tell all of your doctors that you take sildenafil. If you need emergency medical care for a heart problem, it is important that your doctor knows when you last took sildenafil.
Do not use sildenafil if you are also using a nitrate medicine, often used to treat angina or high blood pressure. Nitrate medicines include nitroglycerin, isosorbide, Imdur®, Nitro-Bid®, Nitro-Dur®, Nitrol® ointment, Nitrolingual® spray, Nitrostat®, and Transderm Nitro®. Some illegal ("street") drugs called "poppers" (such as amyl nitrate, butyl nitrate, or nitrite). Do not use sildenafil if you also use riociguat (Adempas®).
If you will be taking sildenafil for pulmonary arterial hypertension, your doctor will want to check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
If you take sildenafil for pulmonary arterial hypertension, 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.
Sildenafil should not be used with any other medicine or device that causes erections.
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.
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.
If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately.
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 already use medicine for high blood pressure (hypertension), sildenafil could make your blood pressure go too low. Call your doctor right away if you have more than one of these symptoms: blurred vision, confusion, dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly, sweating, or unusual tiredness or weakness.
Sildenafil does not protect you against sexually transmitted diseases (including HIV or AIDS). Use protective measures and ask your doctor if you have any questions about this.
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 immediately if any of the following side effects occur:
- Bladder pain
- burning feeling in the chest or stomach
- burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
- cloudy or bloody urine
- increased frequency of urination
- pain on urination
- stomach upset
- tenderness in the stomach area
- Abnormal vision
- behavior change similar to drunkenness
- bleeding of the eye
- blurred vision
- bone pain
- breast enlargement
- chest pain
- cold sweats
- convulsions (seizures)
- cool and pale skin
- deafness or hearing loss
- decrease in amount of urine or the frequency of urination
- decreased vision
- difficulty in concentrating
- dizziness or lightheadedness, especially when getting up suddenly from a lying or sitting position
- double vision
- dry eyes
- dry mouth
- dryness, redness, scaling, or peeling of the skin
- excessive hunger
- eye pain
- fainting or faintness
- fast, irregular, or pounding heartbeat
- feeling of something in the eye
- fever or chills
- headache (severe or continuing)
- increase in the size of the pupil
- increased sweating
- increased thirst
- lower back or side pain
- migraine headache
- nausea (severe or continuing)
- numbness of the hands
- painful, swollen joints
- prolonged, painful erection of penis
- redness, burning, or swelling of the eyes
- redness, itching, or tearing of the eyes
- restless sleep
- seeing shades of colors differently than before
- sensitivity to light
- skin lesions with swelling
- skin paleness
- skin rash, hives, or itching
- skin ulcers
- slurred speech
- sore throat
- sudden weakness
- swelling of the face, hands, feet, or lower legs
- trouble breathing
- twitching of the muscles
- unusual feeling of burning or stinging of the skin
- unusual tiredness or weakness
- vision changes
- vision loss, temporary
Incidence not known
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:
- Aches or pains in the muscles
- bloody nose
- difficult or labored breathing
- pain or tenderness around the eyes and cheekbones
- redness of the skin
- stomach discomfort following meals
- stuffy or runny nose
- trouble sleeping
- unusually warm skin
- Abdominal or stomach pain
- abnormal dreams
- clumsiness or unsteadiness
- diarrhea or stomach cramps (severe or continuing)
- difficulty in swallowing
- ear pain
- increased amount of saliva
- increased skin sensitivity
- lack of coordination
- loss of bladder control
- mental depression
- numbness or tingling of the hands, legs, or feet
- rectal bleeding
- redness or irritation of the tongue
- redness, soreness, swelling, or bleeding of the gums
- ringing or buzzing in the ears
- sensation of motion, usually whirling, either of one's self or of one's surroundings
- sexual problems in men (continuing), including failure to experience a sexual orgasm
- sores in the mouth and on the lips
- tense muscles
- trembling and shaking
- waking to urinate at night
- worsening of asthma
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.
Frequently asked questions
More about sildenafil
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- Drug class: agents for pulmonary hypertension
- Drug Information
- Sildenafil injection
- Sildenafil Intravenous (Advanced Reading)
- Sildenafil Tablets (Erectile Dysfunction)
- Sildenafil Tablets (PAH)
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