Erectile dysfunction treatment
Sildenafil tablets
Sildenafil is the generic form of Viagra. It increases blood flow to the penis when you are sexually aroused, helping you get and keep an erection.
- Works within 30 to 60 minutes
- Effects last around 4 to 6 hours
- The most widely prescribed ED tablet
Available doses
$19
Subscribe & Save treatment price
Indicative treatment price for reference. Sildenafil is a prescription-only medicine in Canada; your prescriber determines the appropriate strength after an assessment.
About sildenafil
What is sildenafil and how does it work?
Sildenafil belongs to a group of medicines called PDE5 inhibitors. Blocking the PDE5 enzyme relaxes the blood vessels supplying the penis, so more blood can flow in during sexual arousal. It does not cause an erection on its own — sexual stimulation is still needed.
Same medicine as Viagra
Sildenafil contains the identical active ingredient to Viagra at the same strengths. Since the patent expired, generic versions cost considerably less.
How effective is it?
In clinical trials around 80% of men taking sildenafil achieved erections firm enough for sex, compared with roughly 17% on placebo.
How quickly does it work?
Most men notice an effect 30 to 60 minutes after taking a tablet. A heavy or fatty meal can delay how quickly it starts working.
At a glance
Sildenafil summary
| Detail | Information |
|---|---|
| What is it? | A prescription treatment for erectile dysfunction in men |
| Active ingredient | Sildenafil citrate |
| Format | Film-coated tablet taken as needed |
| Dose | One tablet 30 to 60 minutes before sex, no more than once in 24 hours |
| How it works | PDE5 inhibitor that increases blood flow to the penis during arousal |
| Effectiveness | Around 8 in 10 men report firmer, longer-lasting erections |
| Duration | Effects typically last 4 to 6 hours |
| Strengths | 25mg, 50mg, 100mg |
| Common side effects | Headache, flushing, nasal congestion, indigestion, dizziness |
How to get sildenafil
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Complete a simple assessment
Answer questions about your health, lifestyle, and goals.
Your assessment is reviewed by a clinician
A Canadian-licensed prescriber carefully reviews your assessment to ensure treatment is safe and suitable for you.
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Your medication is dispensed by our registered pharmacy and delivered to your door in plain packaging.
Stay supported
Schedule reviews with our specialist teams to monitor progress and support you throughout your journey.
How to take and dosage
Sildenafil dosage
50mg is the usual starting dose. Your prescriber may step the dose up or down depending on how you respond and how well you tolerate it.
| Strength | When it is used | Notes |
|---|---|---|
| 25mg | When 50mg is too strong | Often used by men who respond well but experience side effects such as headache or flushing |
| 50mg | Usual starting dose | Most men find this effective. Take 30 to 60 minutes before sex |
| 100mg | When 50mg is not effective | Maximum single dose. Do not start treatment at 100mg |
Never take more than one tablet in 24 hours. Clinicians usually advise trying the same dose on several separate occasions before deciding it has not worked.
How to take sildenafil
Sildenafil is taken only when you need it, not every day.
Timing
- Swallow one tablet whole with water
- Take it 30 to 60 minutes before sex
- Effects last around 4 to 6 hours
- Maximum of one tablet in any 24-hour period
Food and alcohol
- Works fastest on an empty stomach
- A large or fatty meal can delay the effect
- Alcohol can make it harder to get an erection and worsen dizziness
If it does not work first time
Give the same dose a fair trial on several separate occasions before changing anything. Anxiety, alcohol, timing and a heavy meal are common reasons a first attempt disappoints.
Missed doses
There is no missed-dose schedule because sildenafil is taken as needed. Simply take a tablet the next time you plan to have sex.
Side effects
Sildenafil is generally well tolerated and most side effects are mild and short-lived, easing as your body gets used to the medicine.
Common side effects
- Headache and dizziness
- Facial flushing or warm skin
- Blocked or runny nose
- Indigestion, nausea or diarrhoea
- Muscle or back pain
- Blurred vision or altered colour vision
Seek urgent medical help
- An erection lasting more than 4 hours (priapism) — this can cause permanent damage
- Sudden loss of vision in one or both eyes
- Sudden hearing loss or ringing in the ears
- Chest pain during or after sex
Reducing side effects
Headache and flushing often settle with repeated use. If they persist, your prescriber may suggest a lower strength or a different PDE5 inhibitor.
Reporting side effects
Side effects can be reported to Health Canada through the Canada Vigilance Program. Always read the patient information leaflet supplied with your medicine.
Eligibility
Erectile dysfunction can be an early sign of cardiovascular disease or diabetes, so our clinicians assess your overall health, not just your symptoms.
Sildenafil may suit you if
- You are a man aged 18 or over experiencing difficulty getting or keeping an erection
- You want an as-needed treatment rather than a daily tablet
- Your blood pressure and cardiovascular health are stable
- You are able to have your general health reviewed by a clinician
Do not take sildenafil if you
- Take nitrates such as glyceryl trinitrate or isosorbide, or recreational poppers (amyl nitrite)
- Take riociguat for pulmonary hypertension
- Have had a heart attack or stroke in the last 6 months, or have unstable angina
- Have very low blood pressure, severe heart failure or severe liver disease
- Have a hereditary degenerative retinal disorder such as retinitis pigmentosa
- Have had non-arteritic anterior ischaemic optic neuropathy (NAION)
Important safety information
Interactions to flag
- Nitrates and nitric oxide donors — a dangerous drop in blood pressure
- Alpha-blockers such as tamsulosin — risk of dizziness and fainting
- Some HIV protease inhibitors and antifungals raise sildenafil levels
- Other ED medicines should never be combined
Buy from a licensed pharmacy
Counterfeit ED tablets sold without a prescription are common online and may contain the wrong dose or no active ingredient at all. Miva dispenses from a Canadian-registered pharmacy against a valid prescription.
Underlying causes
ED can be linked to diabetes, high blood pressure, high cholesterol, low testosterone, prostate surgery, some medicines, smoking, alcohol, stress or depression. Treating the cause matters as much as treating the symptom.
When to see your own doctor
Book a face-to-face appointment if ED came on suddenly, follows an injury or surgery, or is accompanied by chest pain, breathlessness or reduced exercise tolerance.
Alternatives to sildenafil
Different men respond differently to each PDE5 inhibitor. If one does not suit you, another often will.
Other tablets
- Tadalafil — effects last up to 36 hours, also available as a low daily dose
- Vardenafil — around 5 hours of action, an option if sildenafil causes side effects
- Avanafil — a faster-acting PDE5 inhibitor where available
Non-medicine approaches
- Reducing alcohol and stopping smoking
- Weight management and regular physical activity
- Psychosexual therapy or counselling where anxiety plays a role
- Vacuum erection devices
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Our expert team
Our clinical team of doctors, pharmacists, dietitians and health coaches supports you at every stage. Join over 1,000,000 Canadian patients who trust Miva with their health.
Abdal Alvi
Chief Clinical Officer
MPharm, IP, MRPharmS
Laura Perez
Clinical Nutrition Lead
BSc (Hons), MSc, MSc
Aamina Rafiq
Superintendent Pharmacist
MPharm
Ayisha Mushtaq
Registered Associate Nutritionist
MSc Human Nutrition
Zahra Qureshi
Clinical Pharmacist
MPharm, IP
Richard Wood
Pharmacist
BSc (Hons)
Rebekkah Shaw
Patient Care Lead
BSc (Hons)
Jane Miller
Registered Dietitian
MSc, RD
Sildenafil frequently asked questions
Related treatments
Medically reviewed by
Aamina Rafiq
Superintendent Pharmacist
This page has been reviewed by our clinical team to ensure it is clear, accurate and up to date. Last updated: 10 February 2026.
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