Sildenafil (Oral)

Sildenafil is the active ingredient in Revatio and Viagra that is used for the treatment of erectile dysfunction in men.


Sildenafil is used for the treatment of men who are suffering from erectile dysfunction or sexual impotence. It is the active ingredient in both Revatio and Viagra.

Sildenafil is a member of the group of medicines known as phosphodiesterase 5 inhibitors. Phosphodiesterase type-5 is an enzyme that works in the body and the penis is one such area in which it works. Sildenafil inhibits the enzymes ability to work effectively.

Erectile dysfunction is a medical condition wherein the penis fails to harden and expand, or to stay hard, when a man is sexually stimulated, aroused or excited. The normal bodily response to sexual attraction is the increase of the flow of blood to the penis, but this does not occur with erectile dysfunction. By inhibiting the enzyme phosphodiesterase type-5, Sildenafil helps in maintaining an erection when the penis is stroked. Without physical stimulation, such as stroking or the pressure of sexual intercourse, Sildenafil cannot work and will not cause an erection in the patient.

In addition to the use for the treatment of erectile dysfunction, Sildenafil can also be used in males and females for the treatment of the symptoms of pulmonary arterial hypertension. This form of high blood pressure affects the route between the lungs and the heart, meaning the heart must work far harder to get enough blood into the lungs for the absorption of oxygen. In these patients, Sildenafil works on the same enzyme to relax the blood vessels in the pulmonary arterial tract. This increase the supply of blood to the lungs will, in turn, reduce the pressure being placed on the heart.

This treatment is available as either a powder for suspension or as a tablet. It is available only with a prescription from a doctor for the treatment of pulmonary arterial hypertension. It is available from pharmacists for the treatment of male erectile dysfunction.

Conditions treated

Type of Medicine

  • Phosphodiesterase type-5 inhibitor (PDE5)

Side Effects

In addition to the desired effects of this medication, other unwanted effects may occur. As this medication is used in the treatment of very different conditions, the desired effects for one treatment may also be bothersome for the patient using it for another purpose. Some side effects may occur that will require immediate medical attention. Other side effects will not necessitate medical attention and may abate over time as the body becomes used to the treatment.

The following side effects will necessitate that you seek medical attention from your doctor immediately:

Occurring less commonly:

  • Bladder discomfort or pain
  • Burning or feeling of numbness in the skin
  • Burning sensation in the chest or stomach
  • Clouded or bloody urine stream
  • Dizziness
  • Increased frequency or volume of urination
  • Indigestion
  • Pain during urination
  • Stomach upset or discomfort
  • Tenderness in the stomach area

Occurring only rarely:

  • Abnormal or changed vision
  • Anxiousness
  • Behavior changes that can be likened to drunkenness
  • Bleeding from the eye
  • Blurring of vision
  • Bone pains
  • Breast enlargement
  • Change in the perception of colors
  • Chest pains
  • Chills when warm
  • Cold sweats
  • Confusion or disorientation
  • Convulsions, seizures or fitting
  • Cool, pale skin
  • Deafness or decrease in quality of hearing
  • Decrease in the volume or frequency of urination
  • Decreased vision quality
  • Difficulty concentrating
  • Dizziness or feeling of lightheadedness when rising rapidly.
  • Double vision
  • Drowsiness or extreme tiredness
  • Dry eyes
  • Dry mouth or feeling of dehydration
  • Dryness or peeling of the skin
  • Excessive appetite
  • Eye pains
  • Fainting or feeling of faintness
  • Fast pounding heartbeat
  • Feeling of something stuck in the eye
  • Fever or chills
  • Headache that is ongoing
  • Hives
  • Increased size of the pupils
  • Increased sweating without reason
  • Increased thirstiness
  • Lower back pain and/or pains in the side
  • Migraine headaches
  • Nausea that is ongoing
  • Nervous feelings
  • Nightmares
  • Numbness of the hands and/or fingers
  • Pain or swelling of the joints
  • Prolonged and painful erection or hardening of the penis
  • Redness or swelling of or around the eyes
  • Redness or tearing of the eyes
  • Restless when sleeping
  • Sensitivity to light
  • Shakiness or trembling
  • Skin lesions with or without swelling
  • Skin paling
  • Skin rash or itchiness
  • Skin ulcerations
  • Slurring of the speech
  • Soreness of the throat
  • Sudden feeling of weakness
  • Swelling of the face, lower legs, feet or hands
  • Troubled breathing
  • Twitching of the muscles involuntarily
  • Unusual feeling of stinging or burning of the skin
  • Unusual tiredness
  • Unusual weakness
  • Vision perception changes
  • Vision loss or decrease in quality

Frequency of incidence not known:

Other side effects can occur that will not require you to seek medical attention. These side effects will usually abate over time as your body gets used to the treatment, but in some cases they can be ongoing. If these side effects are ongoing or become bothersome then you should speak to your medical professional for advice on how to alleviate the discomfort. In most cases, however, the following side effects will not necessitate the seeking of medical attention:

Occurring commonly:

  • Aching in the muscles
  • Bleeding nose
  • Blocked or runny nose
  • Diarrhea
  • Difficulty breathing or labored breath
  • Flushing or redness
  • Headaches
  • Muscle pains
  • Pain or tenderness of the area around the eyes and cheekbones
  • Redness of the skin
  • Sneezing
  • Stomach discomfort after eating
  • Troubled sleep
  • Unusually warm skin

Occurring only rarely:

  • Abdominal pain or stomach discomfort
  • Abnormal or unusual dreams
  • Anxiousness
  • Bleeding of the gums
  • Clumsiness or unsteadiness
  • Coughing
  • Diarrhea or stomach cramps that are ongoing
  • Difficulty in swallowing
  • Ear pains
  • Failure to experience a sexual orgasm
  • Feeling that the surroundings or oneself are constantly moving
  • Increased amount of salivation
  • Increased skin sensitivity to touch
  • Lack of coordination or motor control
  • Loss of control of the bladder
  • Mental depression or extreme sadness
  • Nausea or feelings of sickness
  • Numbness of the hands, legs, or feet
  • Rectal bleeding
  • Redness, sores or irritation of the tongue
  • Ringing or buzzing heard that isn't there
  • Sexual problems in men that are ongoing
  • Sores in the mouth and on lips
  • Tense muscles
  • Trembling and/or shaking
  • Undue sleepiness
  • Vomiting
  • Waking more frequently to urinate at night
  • Worsening of asthma

Other side effects that have not been listed herein may also occur. If you experience other side effects not listed here then you should report them to your doctor. If you are concerned about your health then you should seek emergency medical attention.


Sildenafil should be taken only as directed by your doctor. You should not change the dose without being directed to by your doctor. Doing so will increase the risk of experiencing side effects and may make side effects more severe.

This medication can be taken with or without food.

Sildenafil comes with a patient medication guide that you should read before use and each time you receive a refill as it may be updated.

If you are taking an oral liquid dose of Sildenafil then you should shake the bottle hard for at least 10 seconds before use each time. Ensure that the oral syringe is properly cleaned and stored after each use.

For erectile dysfunction, this medication will not usually start to work for 30 minutes following dosing. It will continue to work for up to 4 hours, although effects are usually lessened after 2 hours.

Do not change the brand of Sildenafil that you are using as the brands work differently and will not necessarily affect you in the same way.

You should never share your prescription with another person. The prescription is for you alone and should not be shared.

The dose of this medication used will differ for each patient and for the conditions treated. Dosage will depend on the brand, strength, condition, weight and other factors. The following is a guideline for dosage only and you should follow the directions given to you by your doctor. Do not change your dose without discussing doing so with your doctor.

For the treatment of patients suffering from erectile dysfunction:

  • Adults aged up to 65 - 50mg no more frequently than once daily. Take the medication 1 hour before planned sexual intercourse. The dose may be adjusted by your doctor if required.
  • Adults over the age of 65 - 25mg no more than once daily. Take the medication 1 hour before planned sexual intercourse. The dose may be adjusted by your doctor if required.
  • Children - Use is not recommended in children

For the treatment of patients suffering from pulmonary arterial hypertension:

  • Adults - 5-20mg taken thrice daily. Doses should be separated by 4-6 hours.
  • Children - Use and dosage should be determined individually by the doctor.

If you miss a dose of this treatment for pulmonary arterial hypertension then you should take it as soon as possible. If, however, you are close to your next dose then you should skip the missed dose and return to your usual schedule. Do not take double doses of this treatment.


This medication can interact with a range of other medications. In some cases, they will prevent one another from working and in other cases, they can react violently causing serious unwanted side effects. You should inform your doctor of all medications that you are taking before taking a prescription of Sildenafil for either erectile dysfunction or pulmonary arterial hypertension. This includes all herbal remedies, vitamin supplements, over the counter medications and prescription medications. This is especially important if you are taking any of the following.

Sildenafil should not be taken in conjunction with any of the following:

  • Tipranavir
  • Telaprevir
  • Saquinavir
  • Ritonavir
  • Riociguat
  • Propatyl Nitrate
  • Pentaerythritol Tetranitrate
  • Nitroprusside
  • Nitroglycerin
  • Nelfinavir
  • Molsidomine
  • Lopinavir
  • Isosorbide Mononitrate
  • Isosorbide Dinitrate
  • Indinavir
  • Fosamprenavir
  • Erythrityl Tetranitrate
  • Darunavir
  • Cobicistat
  • Boceprevir
  • Atazanavir
  • Amyl Nitrite
  • Amprenavir

If you are taking any of the above then your doctor may need to change one or the other of the prescriptions.

The use of Sildenafil with any of the following would not normally be recommended:

  • Voriconazole
  • Telithromycin
  • Simeprevir
  • Nefazodone
  • Lumacaftor
  • Itraconazole
  • Idelalisib
  • Fluconazole
  • Dihydrocodeine
  • Conivaptan
  • Clarithromycin
  • Ceritinib
  • Cannabis

In some cases, your doctor may prescribe any of the above along with Sildenafil but they may need to change the dose of one or the other medication or may need to change the frequency at which you take them.

The use of the following medications in conjunction with Sildenafil can cause an increase in the risk of experiencing certain side effects:

  • Trimazosin
  • Terazosin
  • Tamsulosin
  • Silodosin
  • Rifapentine
  • Prazosin
  • Nebivolol
  • Moxisylyte
  • Ketoconazole
  • Etravirine
  • Erythromycin
  • Doxazosin
  • Delavirdine
  • Ciprofloxacin
  • Bunazosin
  • Bosentan
  • Alfuzosin

Sometimes both medications may still be the best treatment available for you, but your doctor may wish to change doses or frequency of use. They may also wish to monitor you for unwanted side effects.

Other medications listed herein could possibly cause interactions with Sildenafil. This list has been compiled considering the severity of interactions, but it is vital that you inform your doctor of all medications that you are taking.

Certain medication can also interact with food, drink, alcohol, and tobacco. You should discuss your use of all of these with your doctor before beginning treatment.

With this medication you should avoid consumption of the following fruit juices:

  • Grapefruit juice
  • Pomelo Juice

Other medical problems can also affect the use of certain medications. You need to inform your doctor of all medical conditions from which you suffer or from which you have suffered in the past. This is especially important in the following circumstances:

Caution should be exercised because of an increased risk of complications in patients suffering from:

  • Abnormalities of the penis including extreme curving or birth defects.

Do not use this medication in patients who suffer from the following conditions:

  • Angina
  • Arrhythmia
  • Blood vessel problems
  • Heart attack
  • Heart failure
  • Hypertension
  • Hypotension
  • Retinal disorders
  • Retinitis pimentosa
  • Stroke in the previous 6 months

Patients suffering from the following conditions will be at greater risk of suffering a serious side effect of the eye called NAION:

  • Aged over 50
  • Coronary artery disease
  • Crowded disc in the eye
  • Diabetes
  • Heart disease
  • Hyperlipidemia
  • Hypertension
  • Non-arteritic anterior ischemic optic neuropathy (NAION)
  • Smoking

There is an increased risk of problems occurring in patients suffering from the following:

Prolonged erection of the penis may occur in patients who suffer from the following conditions:

The following condition may be worsened by use of Sildenafil:

  • Pulmonary veno-occlusive disease (PVOD)

Other medical conditions not listed herein may also impact your use of Sildenafil. These conditions have been listed due to severity but it is vital that you inform your doctor of all medical conditions from which you suffer or have suffered in the past.


Before agreeing to the use of any medications you should consider the benefits of use in relation to the risks of taking the medication. This is a decision that should be made with your doctor and you should ensure that you have considered all of the following together in order that you may reach this decision:


You should inform your doctor if you have ever experienced any unusual reactions to medication in the past. You should also inform them if you have allergies to dyes, preservatives, foods, animals or any other substances.


Sildenafil should never be used for the treatment of erectile dysfunction in children. Use should also be avoid for the treatment of pulmonary arterial hypertension, particularly for chronic use.


Elderly patients are more likely to suffer from a few isolated side effects than younger users. They are also more likely to suffer from medical problems that will limit use. However, use may be effective in the elderly in certain circumstances and if used with caution.


There is limited risk to the fetus from the use of Sildenafil in pregnant women. You should, however, discuss use with your doctor. Alternative and safer medications may be determined for use instead.


There are no appropriate studies to determine risk. Weigh the benefits and risks or breastfeeding with your doctor before use.

You must inform all of your doctors that you are using this treatment. It is essential that the medical professional knows of your use if you require emergency medical treatment to your heart at any point. This doctor should know when you last took the medication where it is possible to inform them.

This medication should not be used if you are taking treatments for a range of heart and lung conditions. Ensure that you have informed your healthcare professional of all treatments that you are taking.

When used in the treatment of pulmonary arterial hypertension, patients should have regular check-ups with their doctor to ensure that they are gaining the correct benefits are not suffering from unwanted side effects.

If you are using this medication for the treatment of pulmonary arterial hypertension then you should not take it for the purposes of treating erectile dysfunction. This can lead to an overdose of Sildenafil.

Sildenafil should not be used in conjunction with other treatments that trigger erections.

Sildenafil should not be used in conjunction with other equipment that triggers erections.

Ensure that your doctor is aware of any heart conditions from which you have suffered in the past. This medication can cause serious heart problems where conditions already exist.

You should contact your doctor if your erection has lasted for longer than 4 hours. You may require prompt medical attention to avoid the occurrence of permanent damage to your penis.

If you experience changes to your vision or loss of vision then you should contact your doctor immediately.

If you experience changes to your hearing or loss of hearing then you should contact your doctor immediately.

If you are already taking medication for high blood pressure then Sildenafil use could cause your blood pressure to drop too low.

Contact your doctor if you experience the following symptoms of low blood pressure:

  • Blurring of the vision
  • Confusion or disorientation
  • Dizziness
  • Feeling of faintness
  • Lightheadedness
  • Sweating
  • Unusual tiredness
  • Unusual weakness

This medication is not a contraceptive and does not protect you against sexually transmitted infections, HIV or AIDS. Use protective measures when having sex and discuss this with your doctor if you have any questions.

Do not take any other medications in addition to this treatment unless you have discussed this use with your doctor.


This medication should be stored in the sealed container at room temperature. Keep this medication away from heat, moisture, and direct light. Prevent from freezing.

  • Keep this medication out of the reach of children at all times.
  • Do not keep outdated medication and dispose of unused medications appropriately as directed by your doctor.
  • Unused Revatio liquid medication should be disposed of after 60 days following mixing.


Sildenafil is used in the treatment of two conditions. The first is the treatment of erectile dysfunction or sexual impotence in men. The second is the treatment of pulmonary arterial hypertension in both men and women.

In the treatment of pulmonary arterial hypertension, the drug works to relax the blood vessels in the arteries between the lungs and heart, allowing for the easier flow of blood and the better circulation of oxygen around the body.

In the treatment of erectile dysfunction, the medication inhibits an enzyme that is active in the penis enabling the penis to harden when stroked. The penis will remain hard when stroked, but with normal effects, the penis will soften when left.

Sildenafil is the active ingredient in Viagra and Revatio and is available as a powder to be mixed into a liquid or in tablet form.

When taken for erectile dysfunction the medication should be taken 30 minutes before intercourse. The penis can stay erect for up to 4 hours. If the penis stays hard for longer than this, however, then you may need to seek medical attention. Prolonged erection can cause lasting damage to the penis.

This medication should not be used in conjunction with other medication or equipment designed to give the user an erection. Doing so can lead to damage caused by the occurrence of an overly prolonged erection.

This medication interacts with a wide range of other medications and medical conditions. Patients should share all their medical information with the doctor in deciding whether to take this medication or not.

Patients using this medication for the treatment of pulmonary arterial hypertension should not use it for erectile dysfunction. This can result in too great a dose being taken. Discuss other methods with your doctor.

Last Reviewed:
February 01, 2018
Last Updated:
April 03, 2018
Content Source: