Viagra (Sildenafil): Uses, Dosage, Side Effects and Cost in Canada

Viagra is sildenafil tablets and films for erectile dysfunction in adult men. Learn how it works, usual doses, side effects, who should not take it, cost and how to ask a BC doctor.

sexual healthDoctor-reviewedPrescriptionAvailable in Canada
Illustration of a blister card of tablets for Viagra (sildenafil)

Disclaimer: This article is for informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.

Overview

Viagra is a brand name for sildenafil, a prescription medicine for erectile dysfunction (ED). ED means not being able to get or keep an erection firm enough for sex. Viagra has been authorized in Canada since 1999 and is sold by BGP Pharma ULC, a Viatris company.

Health Canada has authorized Viagra for erectile dysfunction in adult men. It comes as 25 mg, 50 mg and 100 mg tablets and as a 50 mg film that dissolves on the tongue. Generic sildenafil tablets are also sold in Canada. Revatio is a different sildenafil product used for pulmonary arterial hypertension (high blood pressure in the arteries of the lungs) and should not be combined with Viagra.

Viagra needs a prescription. BC residents can speak with a BC-licensed doctor by phone through Avee Health to ask whether it is appropriate for them. The doctor decides based on your health history. A prescription is not guaranteed.

In Canada, Viagra is authorized for:

  • Erectile dysfunction in adult men

In clinical trials it also improved erections in men with diabetes, spinal cord injury or prostate removal surgery. It works only with sexual stimulation and does not increase sex drive.

Viagra is not for women or for anyone under 18. It does not protect against sexually transmitted infections, including HIV.

Generic name

Sildenafil

Drug class

Phosphodiesterase type 5 (PDE5) inhibitor

Category

sexual health

Availability

Prescription required

In Canada

Available

How Viagra Works

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor. During sexual stimulation, the body releases nitric oxide in the penis. This raises the level of a messenger called cGMP, which relaxes smooth muscle and lets more blood flow in. PDE5 is the enzyme that breaks cGMP down. Sildenafil blocks PDE5, so the natural response lasts longer and an erection is easier to get and keep.

Viagra has no effect without sexual stimulation. Sildenafil reaches its highest level in the blood about 60 minutes after a dose taken on an empty stomach (range 30 to 120 minutes), and its half-life is 3 to 5 hours.

Dosage Instructions of Viagra

Your doctor sets your dose. The usual directions in the Canadian product monograph are:

  • Usual dose: 50 mg as needed, about 30 to 60 minutes before sexual activity. It can be taken anywhere from 30 minutes to 4 hours before.
  • The dose can be lowered to 25 mg or raised to 100 mg, depending on how well it works and how you tolerate it.
  • Maximum: 100 mg, and no more than one dose a day
  • A 25 mg starting dose is considered for people aged 65 or older, with liver problems or severe kidney problems, or taking an alpha-blocker or a medicine that raises sildenafil levels. With ritonavir, the maximum is 25 mg in 48 hours.

Tablets: swallow whole with water. Films: place the film on your tongue with a dry finger and let it dissolve completely. You can swallow saliva, but not the film. For a 100 mg dose, take the second film once the first has fully dissolved.

Viagra can be taken with or without food, but a high-fat meal can delay the effect by about an hour.

Missed dose: Viagra is taken only when needed, so there is no missed dose. Do not take more than your prescribed dose or more than one dose a day.

Storage Instructions

Store Viagra between 15°C and 30°C in the original package. Do not use it after the expiry date, and keep it out of the reach and sight of children.

Side Effects of Viagra

In flexible-dose clinical trials, the most common side effects were (Viagra compared with placebo):

  • Headache: 15.8%, compared with 3.9%
  • Flushing: 10.5%, compared with 0.7%
  • Indigestion: 6.5%, compared with 1.7%
  • Stuffy nose: 4.2%, compared with 1.5%
  • Changes in vision: 2.7%, compared with 0.4%. These were mild and short-lived, mostly a blue-green colour tinge, more sensitivity to light or blurred vision.
  • Dizziness: 2.2%, compared with 1.2%

Get medical help right away if you have:

  • An erection that lasts longer than 4 hours. Without prompt treatment it can damage the penis and cause permanent loss of erections.
  • Sudden loss or decrease of vision in one or both eyes
  • Sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness
  • Chest pain, fainting or severe dizziness during or after sex. Stop, call 911, and tell the emergency staff that you took Viagra, because nitrate medicines must not be given with it.
  • Signs of a serious allergic reaction, such as swelling of the face, lips or throat or trouble breathing, or a severe rash with blistering or peeling skin

Important Safety Information About Viagra

  • Nitrates: do not take Viagra if you use any nitrate medicine, such as nitroglycerin, regularly or only now and then, in any form (tablets, under-the-tongue sprays or tablets, patches or inhaled). The combination can cause a life-threatening drop in blood pressure. It is not known when a nitrate can safely be given after a dose of Viagra.
  • Riociguat: do not take Viagra with riociguat or other guanylate cyclase stimulators.
  • Heart and blood vessels: sex puts extra strain on the heart, and ED treatments should not be used by men who have been advised to avoid sexual activity. There are no controlled data in men who had a heart attack, stroke or life-threatening heart rhythm problem in the past 6 months, or who have unstable angina, heart failure, resting blood pressure below 90/50 or above 170/110. Narrowing of the heart's outflow, such as aortic stenosis, also needs caution.
  • Vision: do not take Viagra if you have ever had vision loss from non-arteritic anterior ischemic optic neuropathy (NAION). Tell the doctor if you have retinitis pigmentosa.
  • Prolonged erection: extra caution is needed with sickle cell anemia, multiple myeloma or leukemia, with Peyronie's disease or another deformity of the penis, or if you have had an erection lasting more than 4 hours before.
  • Bleeding disorders and active stomach ulcers: Viagra is used with caution.
  • Low blood pressure: Viagra widens blood vessels. Dizziness or fainting is more likely if you also take an alpha-blocker or other blood pressure medicines.
  • Other ED medicines: combining Viagra with other PDE5 inhibitors, with Revatio or with other ED treatments has not been studied and is not recommended.
  • Allergy: do not take Viagra if you are allergic to sildenafil or any ingredient. The tablets contain lactose.
  • Driving: dizziness and vision changes can occur. Find out how Viagra affects you before you drive or use machines.

Drug Interactions

Tell your doctor and pharmacist about everything you take, including non-prescription products. The main interactions are:

  • Nitrates and riociguat: must never be combined with Viagra
  • Alpha-blockers, such as doxazosin: blood pressure can drop, with dizziness on standing. You should be stable on the alpha-blocker before starting Viagra, and a lower starting dose is considered.
  • Other blood pressure medicines: the effects add up. With amlodipine, blood pressure fell by a further 8 mmHg systolic and 7 mmHg diastolic on average.
  • Ritonavir: raises sildenafil levels about 11-fold. The maximum is 25 mg in 48 hours.
  • Erythromycin, saquinavir, ketoconazole, itraconazole and cimetidine: raise sildenafil levels. A 25 mg starting dose is considered.
  • Rifampin and bosentan: lower sildenafil levels, so Viagra may work less well
  • Grapefruit juice: may raise sildenafil levels slightly
  • Other ED medicines and other sildenafil products, including Revatio: not recommended together

Brands & DIN Number of Viagra

Brand Names

Viagra

DIN (Drug Identification Numbers)

  • 02239766
  • 02239767
  • 02239768
  • 02544172

Key Takeaways

  • 1Viagra is a brand of sildenafil authorized in Canada to treat erectile dysfunction in adult men.
  • 2The usual dose is 50 mg about 30 to 60 minutes before sex, no more than once a day. The maximum dose is 100 mg.
  • 3It only works with sexual stimulation, and a high-fat meal can delay the effect.
  • 4Never take it with nitrates or riociguat. The combination can cause a dangerous drop in blood pressure.
  • 5Headache, flushing and indigestion are the most common side effects.
  • 6Get urgent care for an erection lasting more than 4 hours, sudden vision or hearing loss, or chest pain.
  • 7Viagra needs a prescription. BC residents can ask a BC-licensed doctor by phone whether it is right for them.

Frequently Asked Questions

How long does Viagra take to work?
Most men take it about 30 to 60 minutes before sex. Sildenafil reaches its highest level in the blood about 60 minutes after a dose on an empty stomach, with a range of 30 to 120 minutes. A high-fat meal can delay this by about an hour. It works only with sexual stimulation.
How long does Viagra last?
Viagra can be taken from 30 minutes to 4 hours before sex. Its half-life is 3 to 5 hours, so the effect fades over several hours. If an erection lasts longer than 4 hours, get medical help right away.
How much does Viagra cost in Canada?
The price depends on the pharmacy, the strength, whether you get brand Viagra or generic sildenafil, and your coverage, so ask your pharmacist for a current price.
Does BC PharmaCare cover Viagra?
Coverage depends on your PharmaCare plan and any private insurance, and the rules change. Check with your pharmacist, BC PharmaCare or your insurer before you fill the prescription.
Is there a generic Viagra in Canada?
Yes. Generic sildenafil tablets are authorized in Canada in 25 mg, 50 mg and 100 mg strengths. They contain the same medicine as Viagra, but the colour, shape and non-medicinal ingredients can differ. Your pharmacist can tell you which products are available.
How do I get Viagra in BC?
Viagra needs a prescription. You can see your family doctor, or book a phone visit with a BC-licensed doctor through Avee Health. Visits are covered by MSP with a valid BC health card. The doctor reviews your health history and decides whether Viagra is appropriate. A prescription is not guaranteed. If one is written, it is sent to the pharmacy you choose.
Can I drink alcohol with Viagra?
In a study, a 50 mg dose did not add to the blood-pressure-lowering effect of alcohol at an average blood alcohol level of 0.08%. Alcohol itself can make it harder to get an erection, and Viagra can cause dizziness. Ask your doctor or pharmacist what is safe for you.
Can I take Viagra if I take heart or blood pressure medicine?
It depends on the medicine. Viagra must never be taken with nitrates, such as nitroglycerin, or with riociguat. With alpha-blockers and other blood pressure medicines, blood pressure can drop further, so the doctor may start with 25 mg. Tell the doctor about every heart and blood pressure medicine you take.
Written By
Avee Editorial

Avee Editorial

Avee Editorial Team

Updated:February 25, 2026