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Hair Loss
Erectile Dysfunction
FAQ

Sildenafil Safety Information

Brand Names in Canada

  1. Viagra
  2. Revatio

Descriptions

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.

This medicine is available only with your clinician's prescription.

This product is available in the following dosage forms:

  • Tablet
  • Powder for Suspension

Before Using

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 clinician will make. For this medicine, the following should be considered:

Allergies

Tell your clinician if you have ever had any unusual or allergic reaction to this medicine 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.

Pediatric

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.

Geriatric

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.

Breastfeeding

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.

Drug Interactions

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 clinician may want to change the dose, or other precautions may be necessary. When you are taking this medicine, 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 this medicine with any of the following medicines is not recommended. Your clinician may decide not to treat you with this medication or change some of the other medicines you take.

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

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your clinician may change the dose or how often you use one or both of the medicines.

  • Cannabis
  • Ceritinib
  • Clarithromycin
  • Conivaptan
  • Dihydrocodeine
  • Duvelisib
  • Fluconazole
  • Fosnetupitant
  • Idelalisib
  • Itraconazole
  • Ivosidenib
  • Larotrectinib
  • Lefamulin
  • Lorlatinib
  • Lumacaftor
  • Nefazodone
  • Netupitant
  • Simeprevir
  • Telithromycin
  • Voriconazole

Using this medicine 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 clinician may change the dose or how often you use one or both of the medicines.

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

Other Interactions

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 this medicine 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 clinician may change the dose or how often you use this medicine, 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 this medicine. Make sure you tell your clinician 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 this medicine 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

Use sildenafil exactly as directed by your clinician. Do not use more of it and do not use it more often than your clinician 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 this medicine 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.

This medicine 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 this medicine that your clinician prescribed. Different brands may not work the same way.

Dosing

The dose of this medicine will be different for different patients. Follow your clinician's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your clinician 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 clinician 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 clinician may adjust your dose if needed.
      • Children—Use is not recommended.
  • 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 clinician.

Storage

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

It is important that you tell all of your clinicians that you take sildenafil. If you need emergency medical care for a heart problem, it is important that your clinician knows when you last took sildenafil.

Do not use this medicine 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 this medicine if you also use riociguat (Adempas®).

If you will be taking this medicine for pulmonary arterial hypertension, your clinician will want to check your progress at regular visits. This will allow your clinician 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 clinician about any heart problems you have now or may have had in the past. This medicine 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 clinician 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 clinician immediately.

Check with your clinician 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 clinician 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.

This medicine does not protect you against sexually transmitted diseases (including HIV or AIDS). Use protective measures and ask your clinician if you have any questions about this.

Do not take other medicines unless they have been discussed with your clinician. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

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 clinician immediately if any of the following side effects occur:

Less common

  1. Bladder pain
  2. burning feeling in the chest or stomach
  3. burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  4. cloudy or bloody urine
  5. dizziness
  6. increased frequency of urination
  7. indigestion
  8. pain on urination
  9. stomach upset
  10. tenderness in the stomach area

Rare

  1. Abnormal vision
  2. anxiety
  3. behavior change similar to drunkenness
  4. bleeding of the eye
  5. blurred vision
  6. bone pain
  7. breast enlargement
  8. chest pain
  9. chills
  10. cold sweats
  11. confusion
  12. convulsions (seizures)
  13. cool and pale skin
  14. deafness or hearing loss
  15. decrease in amount of urine or the frequency of urination
  16. decreased vision
  17. difficulty in concentrating
  18. dizziness or lightheadedness, especially when getting up suddenly from a lying or sitting position
  19. double vision
  20. drowsiness
  21. dry eyes
  22. dry mouth
  23. dryness, redness, scaling, or peeling of the skin
  24. excessive hunger
  25. eye pain
  26. fainting or faintness
  27. fast, irregular, or pounding heartbeat
  28. feeling of something in the eye
  29. fever or chills
  30. headache (severe or continuing)
  31. increase in the size of the pupil
  32. increased sweating
  33. increased thirst
  34. lower back or side pain
  35. migraine headache
  36. nausea (severe or continuing)
  37. nervousness
  38. nightmares
  39. numbness of the hands
  40. painful, swollen joints
  41. prolonged, painful erection of penis
  42. redness, burning, or swelling of the eyes
  43. redness, itching, or tearing of the eyes
  44. restless sleep
  45. seeing shades of colors differently than before
  46. sensitivity to light
  47. shakiness
  48. skin lesions with swelling
  49. skin paleness
  50. skin rash, hives, or itching
  51. skin ulcers
  52. slurred speech
  53. sore throat
  54. sudden weakness
  55. swelling of the face, hands, feet, or lower legs
  56. trouble breathing
  57. twitching of the muscles
  58. unusual feeling of burning or stinging of the skin
  59. unusual tiredness or weakness
  60. vision changes
  61. vision loss, temporary

Incidence not known

  1. Blindness

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:

More common

  1. Aches or pains in the muscles
  2. bloody nose
  3. diarrhea
  4. difficult or labored breathing
  5. flushing
  6. headache
  7. pain or tenderness around the eyes and cheekbones
  8. redness of the skin
  9. sneezing
  10. stomach discomfort following meals
  11. stuffy or runny nose
  12. trouble sleeping
  13. unusually warm skin

Rare

  1. Abdominal or stomach pain
  2. abnormal dreams
  3. anxiety
  4. clumsiness or unsteadiness
  5. cough
  6. diarrhea or stomach cramps (severe or continuing)
  7. difficulty in swallowing
  8. ear pain
  9. increased amount of saliva
  10. increased skin sensitivity
  11. lack of coordination
  12. loss of bladder control
  13. mental depression
  14. nausea
  15. numbness or tingling of the hands, legs, or feet
  16. rectal bleeding
  17. redness or irritation of the tongue
  18. redness, soreness, swelling, or bleeding of the gums
  19. ringing or buzzing in the ears
  20. sensation of motion, usually whirling, either of one's self or of one's surroundings
  21. sexual problems in men (continuing), including failure to experience a sexual orgasm
  22. sleepiness
  23. sores in the mouth and on the lips
  24. tense muscles
  25. trembling and shaking
  26. vomiting
  27. waking to urinate at night
  28. 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 clinician for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.


Portions of this document last updated: March 09, 2021

Original article: https://www.mayoclinic.org/drugs-supplements/sildenafil-oral-route/description/drg-20066989