Viagra® for Erectile Dysfunction: Uses, Dosage, and Safety

What Viagra® Is and How It Works

Viagra® (sildenafil citrate) is a prescription tablet for erectile dysfunction in adult men. It helps increase blood flow to the penis during sexual stimulation. Viagra supports firmer, longer-lasting erections and improved sexual performance when used as directed.

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Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor. Sexual arousal triggers nitric oxide release, which raises cyclic guanosine monophosphate (cGMP). By blocking PDE5, sildenafil helps cGMP last longer in penile tissue. This relaxes smooth muscle in the corpus cavernosum and increases arterial inflow. Sexual stimulation is required for Viagra to work.

Tablets are typically available in 25 mg, 50 mg, and 100 mg strengths. Most people use it as needed, not every day. Onset is usually 30 to 60 minutes. A high-fat meal may delay absorption. Effects can last about four hours.

Learn more about the condition in our Erectile Dysfunction section or read our guide, Viagra Pill How It Works Benefits And Side Effects.

Dosage and Usage

• Typical starting dose: 50 mg taken as needed about 1 hour before sexual activity.
• Your prescriber may adjust to 25 mg or 100 mg based on response and tolerability.
• Do not take more than one dose per day.
• Swallow tablets with water. You can take with or without food.
• A high-fat meal can delay onset by up to an hour.
• Avoid grapefruit or grapefruit juice, which can raise sildenafil levels.
• If you planned activity and forgot to take it, take a dose when appropriate. Do not double the dose.
• Use 25 mg as a starting dose when taking strong CYP3A4 inhibitors (such as ritonavir, ketoconazole, or clarithromycin).
• Do not use with any nitrates (for chest pain) or with riociguat. This combination can cause dangerous drops in blood pressure.
• Use caution with alpha-blockers for prostate or blood pressure. Start at a lower dose or separate dosing times as advised.

• Store tablets at 15–30 °C (59–86 °F) in a dry place, away from moisture and light.
• Keep in the original blister or bottle with the pharmacy label.
• Do not use tablets past the printed expiration date.
• When traveling, keep medicine in your carry-on, not checked baggage.
• Avoid heat exposure in cars or near heaters and direct sun.
• Carry your prescription paperwork at borders and follow local import rules.
• Keep out of reach of children and pets.

Benefits and Savings

Viagra improves erectile function scores and intercourse success in a wide range of men. Many report greater confidence, firmer erections, and better satisfaction with sexual activity. On-demand dosing supports flexibility. For some, a lower dose still works well with fewer side effects.

Buying from Canada can offer meaningful savings. Typical customers save 60–80% compared with common US retail pricing. Multi-month supplies and bulk promotions can reduce the per-month cost even more. Reorder reminders help you stay prepared so you are not caught short before travel or special events.

Many shoppers compare options for cheap Viagra online. You can also consider generic sildenafil for additional savings if appropriate for your prescription.

For current offers, see our Viagra coupon.

Side Effects and Safety

• Headache
• Flushing or warmth in the face or chest
• Indigestion or stomach discomfort
• Nasal congestion or runny nose
• Dizziness or lightheadedness
• Visual changes such as a blue tint or blurred vision
• Back or muscle aches
• Skin redness or mild rash

Serious effects are uncommon but need urgent care. These include chest pain, fainting, prolonged erection lasting more than four hours (priapism), sudden vision loss (including non-arteritic anterior ischemic optic neuropathy), sudden hearing loss, severe allergic reactions, or signs of stroke. Do not use Viagra with nitrates or riociguat due to the risk of profound hypotension. Limit alcohol, which can worsen dizziness and erection quality.

Onset Time

Most people feel an effect within 30 to 60 minutes. A high-fat meal can push onset closer to 60–120 minutes. The window of benefit is typically four hours. Some may notice reliable results only after trying the medication on several occasions while adjusting timing. If a different strength is needed, prescribers can adjust after assessing response and tolerability.

Compare With Alternatives

Tadalafil offers a longer duration. Many choose it for a 24–36 hour window, which supports more spontaneity. It is available as needed or once-daily dosing. See the option here: Cialis®.

Generic sildenafil contains the same active ingredient as Viagra. It has comparable efficacy when taken correctly and often costs less per tablet. Compare the brand with Sildenafil if your prescriber allows substitution.

Other PDE5 inhibitors, such as vardenafil and avanafil, may be considered when response or tolerability differs. Each has unique timing, interactions, and side-effect profiles that clinicians weigh against your medical history.

Combination Therapy

• With alpha-blockers for prostate symptoms: start sildenafil at a lower dose or separate dosing times to reduce dizziness.
• With antihypertensives: monitor blood pressure, as additive effects can occur.
• With testosterone therapy: may help when true hypogonadism is documented.
• With counseling or sex therapy: addresses performance anxiety and relationship factors.
• Do not combine with other PDE5 inhibitors or nitrates.
• Avoid recreational “poppers” (amyl or butyl nitrite), which act like nitrates.

Patient Suitability and Cost-Saving Tips

Viagra is for adult men with erectile dysfunction. It is not for women or anyone under 18. It may be unsuitable for people advised to avoid sexual activity due to cardiovascular risk. Those with recent stroke or heart attack, unstable angina, severe hypotension, or advanced heart failure require careful evaluation.

Do not use Viagra with any nitrates or with riociguat. Use caution in retinitis pigmentosa, a history of NAION, severe liver disease, or significant kidney impairment. Strong CYP3A4 inhibitors can raise sildenafil exposure; a lower starting dose is often used. Grapefruit can also increase levels.

For value, compare brand and generic options and tablet strengths. Larger pack sizes can lower the per-pill price. Bulk promotions may extend savings over several months. You can set simple reorder reminders in your account to avoid gaps before travel. If pill splitting is being considered, speak with a pharmacist about scored options and dose accuracy.

If erectile issues relate to other conditions, coordinated care can help. Diabetes, hypertension, and prostate problems often contribute to symptoms. Explore more background in our article, Early Erectile Dysfunction Symptoms To Watch For, and read about treatment choices in What Is Tadalafil The Ed Medication You Should Know About.

Authoritative Sources

Pfizer Canada: Viagra product page

Drugs@FDA: Viagra (sildenafil) NDA 020895

Health Canada Drug Product Database

Order Viagra® from YouDrugstore: add to cart, upload your prescription, and we ship with prompt, express, cold-chain handling.

This material is for educational use and does not replace advice from your healthcare professional. Always follow your prescriber’s directions and the patient information that comes with your medication.