What Is Viagra (Sildenafil)? Full Guide

What exactly is Viagra?

Viagra is the original brand name of the active ingredient sildenafil, launched by Pfizer in 1998 and part of the PDE5 inhibitor family. Its patent has long expired, so generic sildenafil is now made by many manufacturers worldwide — such as Sidegra, produced in Thailand, and Kamagra from India. They contain the same active ingredient at comparable doses; what differs is the manufacturer and the format.

What does Viagra do — how it works

The straight answer: Viagra improves blood flow into the penis when you are sexually aroused, so the erection becomes full and lasts long enough for sex. The drug blocks PDE5, the enzyme that breaks down the natural blood-vessel-dilating signal in the penis.

What Viagra does not do: it does not increase desire, does not cause erections without stimulation, does not increase size, and does not protect against sexually transmitted infections.

How long does Viagra last?

It starts working within 30-60 minutes of taking it, and the active window lasts around 4-6 hours — meaning "the period when your body can respond", not a continuous hours-long erection.

Worth knowing: a fatty or heavy meal noticeably slows absorption. For the fastest effect, take it on an empty stomach or after a light meal, and avoid drinking heavily.

How to take Viagra correctly

• Take 1 tablet about 1 hour before sex
• The standard starting dose is 50 mg — a doctor may adjust it to 25 mg or 100 mg based on your response and health
• Never take it more than once a day, and never raise the dose yourself because it feels "not strong enough" — ask a doctor or pharmacist first
• Avoid grapefruit juice, which can push blood levels of the drug abnormally high

Side effects and who should not use it

Common side effects are usually mild and pass on their own: headache, facial flushing, feeling warm, blocked nose, indigestion, dizziness, and occasionally a temporary blue tint to vision.

Do not use — or talk to a doctor first — in these cases

• You take nitrate medicines, such as under-the-tongue heart tablets — absolutely contraindicated; blood pressure can drop to life-threatening levels
• Severe heart disease, a recent heart attack or stroke, or blood pressure that is uncontrolled — whether too low or too high
• Severe liver or kidney disease — a lower dose may be needed

Danger signs that need a doctor immediately: a painful erection lasting more than 4 hours (priapism), sudden loss of vision or hearing, or chest pain during sex.

Can women take Viagra?

Viagra is approved for men only. Some research has explored sildenafil for women but the evidence is still limited, and there are sildenafil products marketed specifically for women, such as Lovegra Oral Jelly. Women who are interested should always talk to a doctor first — especially if pregnant, breastfeeding, or living with a medical condition.

Where to buy Viagra — beware of fakes

In Thailand, sildenafil should only be bought from licensed sources. The big problem with the online market is counterfeit Viagra — no active ingredient, the wrong dose, or contaminated with other substances. How to spot the genuine article: sharp, clean packaging, a lot number and expiry date, an intact blister pack, and a seller you can verify — an unusually cheap price is the first warning sign of a fake.

📖 Read more: What Is Sidegra? Thailand's Own Sildenafil · What Is Kamagra Oral Jelly?

Frequently asked questions

Are Viagra and generic sildenafil the same thing?

Yes — Viagra is simply the original brand name for sildenafil. Generics such as Sidegra and Kamagra contain the identical active ingredient, so at the same dose the effect is equivalent.

What does taking Viagra feel like?

Once it kicks in, most men feel nothing "special" until sexual stimulation begins — then erections come easier and fuller than before. Some feel facial warmth, flushing or a slightly blocked nose, which are normal side effects.

What is the difference between Viagra and Sidegra?

Same active ingredient — sildenafil. Viagra is the original brand; Sidegra is a generic made in Thailand. At the same dose the effectiveness is equivalent; the difference is price and manufacturer.

Can I buy Viagra at a pharmacy?

Only licensed pharmacies with a pharmacist on duty can sell it, not every shop keeps it in stock, and convenience stores do not carry it. Ordering from a verifiable specialist online store is the more convenient and more private option.

Can I take it every day?

Do not take it more than once a day. If you feel you need it daily, talk to a doctor — low-dose daily tadalafil may suit you better; see our Cialis (Tadalafil) guide.

References

1. NHS — Sildenafil (Viagra)
2. MedlinePlus — Sildenafil
3. NHS — Erection problems (erectile dysfunction)