Sildenafil belongs to a group of medications called phosphodiesterase type 5 inhibitors. It is used for the treatment of erectile dysfunction (male impotence). It helps to achieve and keep an erection sufficient for sexual activity. It does this by allowing a greater blood flow into the penis when a man is sexually aroused. It works only with sexual stimulation and does not increase sexual desire.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual recommended dose is 50 mg taken as needed, approximately 30 to 60 minutes before sexual activity. However, the medication may be taken any time from 4 hours to half an hour before sexual activity. Based on the effectiveness and side effects of the medication, the dose may be increased to 100 mg or decreased to 25 mg.

The maximum recommended dose is 100 mg and it is not recommended to take more than one dose per day. Sildenafil may be taken with or without food, but taking it with a high-fat meal may increase the time before the medication starts working.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. Do not take higher doses of this medication than those prescribed by your doctor. Contact your doctor if you take a greater dose of sildenafil than prescribed.

Store this medication in its original package at room temperature, protect it from moisture, and keep it out of the reach of children.

25 mg
Each blue, diamond-shaped, coated tablet, debossed with "SD" and "25" on one side and plain on the other side, contains sildenafil citrate equivalent to 25 mg of sildenafil. Nonmedicinal ingredients: colloidal silicon dioxide, corn starch, FD&C Blue No. 2/Indigo Carmine Aluminum Lake, hydroxypropyl methylcellulose, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone, sodium lauryl sulphate, sodium starch glycolate, and titanium dioxide.

50 mg
Each blue, diamond-shaped, coated tablet, debossed with "SD" and "50" on one side and plain on the other side, contains sildenafil citrate equivalent to 50 mg of sildenafil. Nonmedicinal ingredients: colloidal silicon dioxide, corn starch, FD&C Blue No. 2/Indigo Carmine Aluminum Lake, hydroxypropyl methylcellulose, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone, sodium lauryl sulphate, sodium starch glycolate, and titanium dioxide.

100 mg
Each blue, diamond-shaped, coated tablet, debossed with "SD" and "100" on one side and plain on the other side, contains sildenafil citrate equivalent to 100 mg of sildenafil. Nonmedicinal ingredients: colloidal silicon dioxide, corn starch, FD&C Blue No. 2/Indigo Carmine Aluminum Lake, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone, sodium lauryl sulphate, sodium starch glycolate, and titanium dioxide.

Do not take sildenafil if you:

• are allergic to sildenafil or any ingredients of this medication
• are taking any type of nitrate medication in any form (oral, sublingual [under the tongue], skin patch, or spray). Nitrate medications include nitroglycerin and related medications that are used for the relief of chest pain or angina. They also include amyl nitrite "poppers." Use of these medications with sildenafil could cause a sudden severe drop in blood pressure that could lead to dizziness, fainting, heart attack, or stroke.
• are taking the medication riociguat
• have been advised by your doctor not to engage in sexual activity
• have a history of vision problems related to nerve damage to the retina caused by decreased blood flow

Nitrates are found in medications that are used to treat angina (chest pain). If you are not sure if you are taking nitrates, ask your doctor or pharmacist.

Nitrates must NOT be taken by anyone who is using sildenafil because they can cause your blood pressure to drop very low. This may cause dizziness, fainting, heart attack, or stroke.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain
• cough
• diarrhea
• dizziness, particularly when rising from a sitting or lying position
• dry mouth or nose
• fever
• flushing
• headache
• heartburn
• increased frequency of cold- or flu-like symptoms (e.g., fatigue, sore throat, stuffy or runny nose)
• nausea
• sleepiness
• stuffy nose
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• decreased sensation in the mouth
• dizziness, if severe
• low blood pressure
• muscle aches
• nosebleeds
• shortness of breath
• sudden loss or decrease of hearing
• symptoms of irregular heartbeat (e.g., chest pain; dizziness; rapid, pounding heartbeat; shortness of breath)
• temporary memory loss
• throat tightness
• vision changes, including blurred vision, seeing shades of colours differently than before, sensitivity to light, temporary or partial vision loss, or double vision

Stop taking the medication and seek immediate medical attention if any of the following occur:

• chest pains, an irregular heartbeat, or shortness of breath when starting or following sexual activity (if you have a heart condition)
• prolonged (longer than 4 hours), painful, or inappropriate erection of penis
• seizures
• signs of an allergic reaction (e.g., rash; itching; shortness of breath; swollen face, lips, or throat)
• signs of bleeding from the lungs (e.g., difficulty breathing; bluish colouring of the lips; and cool, clammy skin)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• signs of stroke (e.g., sudden or severe headache; sudden loss of coordination; vision changes; sudden slurring of speech; or unexplained weakness, numbness, or pain in arm or leg)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Alcohol: Consumption of alcohol in large amounts may decrease the ability to get an erection and may also temporarily decrease blood pressure, causing dizziness and fainting.

Blood pressure: Tell your doctor if you are taking medications to treat high blood pressure. The combination of these medications and sildenafil may add to the blood pressure-lowering effect of these medications. You should also let your doctor know if you have or have had low blood pressure.

Driving: Sildenafil may cause dizziness or temporary vision changes, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how this medication affects you.

Grapefruit juice: Grapefruit juice can increase the amount of sildenafil in your bloodstream. Do not drink grapefruit juice when taking this medication.

Hearing problems: If you experience a sudden decrease or loss of hearing, seek medical attention immediately.

Heart conditions: If you have or have had heart disease or a heart attack or stroke, speak to your doctor before taking any medication for erectile dysfunction. If chest pains, dizziness, or nausea are experienced during sex, stop the exertion and inform your doctor.

Kidney problems: If you have poor kidney function, you may need lower doses of this medication. Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have kidney problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: If you have poor liver function, you may need lower doses of this medication. Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Nitrate-containing medications: Sildenafil should never be taken with any medications that contain nitrates. Blood pressure may suddenly drop to life-threatening levels if sildenafil is taken with any nitrate-containing medication (e.g., nitroglycerin tablets, spray, or patches) or any other nitrates (e.g., isosorbide dinitrate or amyl nitrite "poppers"). Dizziness, fainting spells, heart attack, or stroke may be experienced.

If use of a nitrate-containing medication is considered medically necessary, you must wait 48 hours after the last dose of sildenafil before taking a nitrate, and only under close medical supervision.

Penis deformation: As with other medications for erectile dysfunction, men with an anatomical deformation of the penis such as angulation, cavernosal fibrosis, or Peyronie's disease should be closely monitored by their doctors if they take this medication.

Prolonged erection: If an erection lasts longer than 4 hours (a rare occurrence), seek immediate medical assistance. If this condition is not treated quickly, tissue damage and permanent loss of the ability to have an erection could result.

Prostate problems: Tell your doctor if you are taking medications, such as alpha-blockers (e.g., doxazosin), to treat prostate problems, as the combination of these medications with sildenafil may add to the blood-pressure-lowering effect of these medications.

Sexually transmitted infections: Sildenafil does not protect against sexually transmitted infections such as HIV.

Vision problems/eye conditions: If you experience a sudden loss of vision in one or both eyes or other vision-related problems, contact your doctor immediately. Vision loss may be partial or complete. While in some cases the condition may improve over time, it can also be permanent.

This rare condition is more likely to occur if you have heart disease, high blood pressure, high cholesterol, diabetes, or eye problems, are more than 50 years old, or if you smoke. If you have any eye conditions, such as retinitis pigmentosa or non-arteritic anterior ischemic optic neuropathy (NAION), tell your doctor.

Pregnancy and breast-feeding: Sildenafil is not intended for use by women.

Children: Sildenafil is not intended for use by children or adolescents under 18 years of age.

Seniors: If you are 65 years of age or older, you may need a lower dose of this medication.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.