Sildenafil

What is Sildenafil and why it's prescribed?

Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors or Viagra. These medicines prevent an enzyme in the body called phosphodiesterase type-5 from working too quickly and relaxes blood vessels, increasing the supply of blood to the body and lungs and reduces the workload of the heart.

It can be used in both men and women to treat the symptoms of Raynaud's and pulmonary arterial hypertension. Hypertension 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.

This medicine is available only with your doctor's prescription. This product is available in the following dosage forms:

  • Powder for Suspension
  • Tablet
  • Before taking treatment

Sildenafil may not be suitable for you if you:

  • are also taking medicines or drugs that contain nitrates – organic nitrates are often used to treat angina and amyl nitrate is a recreational drug commonly known as "poppers"
  • have a severe liver problem
  • have recently had a heart attack or stroke
  • have severe low blood pressure (hypotension)
  • have certain eye conditions

Allergies

Tell your doctor 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.

Paediatric

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.

  • Pregnancy and Breastfeeding
  • Sildenafil is not recommended in pregnancy and whilst breastfeeding.
  • Tell your doctor if you're trying to get pregnant, become pregnant or want to breastfeed.

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 doctor 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 doctor 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 doctor may change the dose or how often you use one or both of the medicines.

Cannabis, Ceritinib, Clarithromycin, Conivaptan, Dihydrocodeine, Fluconazole, Idelalisib, Itraconazole, Lumacaftor

Nefazodone, 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 doctor 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.

How to take it, how long for and long it takes to work?

Sildenafil tablets are usually taken three times a day.

You may need to spend a day in hospital when you start treatment, before returning home and carrying on taking the medicine. How long you can take sildenafil for will depend on your condition. If at any time your condition gets worse, you may be given additional treatment as well as, or instead 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 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.
  • Use only the brand of this medicine that your doctor prescribed. Different brands may not work the same way.
  • The dose of this medicine 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 this medicine. 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 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.

Getting the most of your treatments

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • 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.

What are the possible risks or side-effects?

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.


Check with your doctor immediately if any of the following side effects occur. 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:

Most common

  • Aches or pains in the muscles
  • bloody nose
  • diarrhea
  • difficult or labored breathing
  • flushing
  • headache
  • pain or tenderness around the eyes and cheekbones
  • redness of the skin
  • sneezing
  • stomach discomfort following meals
  • stuffy or runny nose
  • trouble sleeping
  • unusually warm skin


  • How to store treatment

  • 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.

    Information sourced from the Mayo Clinic and the NHS.
  • Related information