Is Revatio the same as Viagra?

Same molecule, different products. Revatio is sildenafil for pulmonary arterial hypertension in adults and in children from one year old, given as a 20 mg tablet three times a day, as a 10 mg/mL oral suspension, or as a 10 mg/12.5 mL intravenous injection. Viagra is sildenafil for erectile dysfunction, 25, 50 or 100 mg, at most once a day. Each label tells the patient not to take the other.

How long before sex should Viagra be taken?

The label's instruction is "approximately 1 hour before sexual activity", with a permitted window: "However, VIAGRA may be taken anywhere from 30 minutes to 4 hours before sexual activity." Peak plasma concentration is reached in 30 to 120 minutes, median 60 minutes, in the fasted state. A high-fat meal pushes the peak back a full hour and cuts it by 29%, the largest food effect of the four oral PDE5 inhibitors.

How long does Viagra last?

The label documents effect up to 4 hours, and says in the same sentence that it was already fading: "The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours." That is a window for activity, not a measure of how long the drug is in the body — sildenafil and its active metabolite both have terminal half-lives of about 4 hours.

Does a starting dose change with age or kidney function?

On this label, yes: "Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance <30 mL/minute)." On the Revatio label for the same molecule, no: it states that no dose adjustment is required, including for severe impairment below 30 mL/min. Two labels, one drug, opposite instructions — because the dose sizes and frequencies being corrected are different.

Can Viagra be taken with nitrates?

No. It is an absolute contraindication on this label, not a caution: sildenafil "was shown to potentiate the hypotensive effects of nitrates, and its administration to patients who are using nitric oxide donors such as organic nitrates or organic nitrites in any form either regularly and/or intermittently is therefore contraindicated." That covers nitroglycerin, isosorbide, and amyl or butyl nitrite "poppers". The label also declines to say when a nitrate becomes safe afterwards, which is not the same as saying no wait is needed.

Why does the dose drop to 25 mg with ritonavir?

Because the interaction is eleven-fold. The label states: "The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold." That is the only circumstance in which this label replaces the once-per-day ceiling with a once-per-48-hours one. Strong CYP3A4 inhibitors such as ketoconazole, itraconazole or erythromycin get a 25 mg starting dose without the 48-hour rule.

Is there a Viagra tablet smaller than 25 mg?

Not under this brand. Section 3 lists three strengths only — 25 mg, 50 mg and 100 mg — as blue, film-coated, rounded-diamond-shaped tablets debossed VGR25, VGR50 or VGR100. A 20 mg sildenafil tablet exists, but it is the Revatio strength, a white round tablet engraved RVT20 intended to be taken three times a day for a lung condition.

Brand — one of two labels for one molecule

Viagra

Q: What is the maximum dose of Viagra?

100 mg, once in a day. The label pairs two sentences: "Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg" and "The maximum recommended dosing frequency is once per day." Both are facts about this brand. The same molecule as Revatio is 20 mg three times a day, titratable to 80 mg three times a day, so a sildenafil ceiling quoted without a brand name means nothing.

Q: Can Viagra be taken with nitrates?

No. It is an absolute contraindication on this label, not a caution: sildenafil "was shown to potentiate the hypotensive effects of nitrates, and its administration to patients who are using nitric oxide donors such as organic nitrates or organic nitrites in any form either regularly and/or intermittently is therefore contraindicated." That covers nitroglycerin, isosorbide, and amyl or butyl nitrite "poppers". The label also declines to say when a nitrate becomes safe afterwards, which is not the same as saying no wait is needed.

Q: Why does the dose drop to 25 mg with ritonavir?

Because the interaction is eleven-fold. The label states: "The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold." That is the only circumstance in which this label replaces the once-per-day ceiling with a once-per-48-hours one. Strong CYP3A4 inhibitors such as ketoconazole, itraconazole or erythromycin get a 25 mg starting dose without the 48-hour rule.

Q: Is there a Viagra tablet smaller than 25 mg?

Not under this brand. Section 3 lists three strengths only — 25 mg, 50 mg and 100 mg — as blue, film-coated, rounded-diamond-shaped tablets debossed VGR25, VGR50 or VGR100. A 20 mg sildenafil tablet exists, but it is the Revatio strength, a white round tablet engraved RVT20 intended to be taken three times a day for a lung condition.

The 100 mg ceiling and the once-a-day rule belong to this brand, not to sildenafil. The same molecule is sold as Revatio at 20 mg three times a day, every day, to adults and to children — and each label tells the patient not to take the other.

Molecule: sildenafil
Manufacturer: Pfizer Laboratories Div Pfizer Inc
Products under this name: 1
Last reviewed: September 2026

Why "sildenafil" does not tell you the dose or the limit

Sildenafil is approved in the United States under two brand names owned by the same company. VIAGRA (NDA020895) is a tablet for erectile dysfunction, taken as needed, at most once a day, at 25, 50 or 100 mg. REVATIO is a treatment for pulmonary arterial hypertension approved as tablets (NDA021845), an intravenous injection (NDA022473) and a powder for oral suspension (NDA203109), taken 20 mg three times a day on a fixed schedule with no reference to sexual activity at all.

The numbers do not line up in any direction. Viagra caps a day at 100 mg. Revatio starts at 60 mg a day and its label permits titration to 80 mg three times a day — 240 mg a day, well over twice the Viagra ceiling, taken indefinitely rather than occasionally. Viagra is not indicated in anyone under 18; Revatio is indicated in children from one year old, dosed by weight. And a man who already holds a Revatio prescription is told by his own label not to take Viagra: "Inform patients taking REVATIO not to take VIAGRA or other PDE‑5 inhibitors."

That means the sentence "sildenafil’s maximum dose is 100 mg" is not a fact about sildenafil. It is a fact about one of its two brands, and it stops being true the moment the box changes. The table below separates what belongs to Viagra from what belongs to the molecule, and the first section after it is the nitrate contraindication, which belongs to both and to every other drug in the class.

What is true of Viagra and not of sildenafil

Each row is something a reader would reasonably assume belongs to the molecule, and does not. These are the facts that change when the brand name on the carton changes, while the drug inside it does not.

Attribute	Viagra	Elsewhere, same molecule
How much may be taken in a dayThe most repeated fact about this drug, that you must not exceed 100 mg or take it more than once a day, is a property of the Viagra application alone. It is not a property of sildenafil, and a man on Revatio is taking more sildenafil in a day than any Viagra prescription permits.	100 mg, once. The label pairs "a maximum recommended dose of 100 mg" with "The maximum recommended dosing frequency is once per day", so 100 mg is both the largest dose and the whole day's allowance.	Revatio is 20 mg three times a day for adults — 60 mg daily as standard — and its label permits titration "to a maximum of 80 mg three times a day, if required, based on symptoms and tolerability", which is 240 mg in a day, taken every day.
What form the drug comes inSildenafil is an injectable drug and a liquid drug, but not under this brand. Anyone searching for "liquid sildenafil" or "sildenafil injection" has left the Viagra label entirely and is reading about a pulmonary product dosed three times a day.	A film-coated tablet in three strengths, 25 / 50 / 100 mg, and nothing else. There is no Viagra injection, liquid or suspension.	Revatio is three dosage forms under one label: a 20 mg tablet, a single-use vial of 10 mg/12.5 mL for intravenous bolus injection, and a powder reconstituted with 90 mL of water to a 10 mg/mL oral suspension with a 60-day shelf life.
Who it may be given toOne molecule, one child, two opposite labelled positions. The paediatric Revatio section also reports a dose-related imbalance in deaths in the STARTS trials, which is the kind of context that vanishes when a dose is quoted as a "sildenafil" figure rather than a brand one.	Adults only. "VIAGRA is not indicated for use in pediatric patients. Safety and effectiveness have not been established in pediatric patients."	Revatio is indicated in pediatric patients 1 to 17 years old for pulmonary arterial hypertension, dosed by weight — 10 mg three times a day at 20 kg or under, 20 mg three times a day above it.
What to do about severe kidney impairmentTwo FDA labels for the same molecule give contradictory renal instructions, because the dose sizes and the dosing frequencies they are correcting are different. A creatinine clearance below 30 changes the Viagra starting dose and does not change the Revatio one.	Reduce the dose. "Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance <30 mL/minute)."	The Revatio label says the opposite in one line: "No dose adjustment is required (including severe impairment CLcr <30 mL/min)." For hepatic impairment it likewise states no adjustment is required for mild to moderate impairment.
Whether the two brands may be combinedBoth labels anticipate exactly this mistake, which is the strongest evidence that the two brands are routinely confused. A man on Revatio asking for Viagra for erectile dysfunction is asking to double a drug he is already taking three times a day.	No, and the label says so in the patient-facing section as well as the clinical one: "Physicians should inform patients not to take VIAGRA with other PDE5 inhibitors including REVATIO or other pulmonary arterial hypertension (PAH) treatments containing sildenafil."	The Revatio label mirrors it from the other side: "Sildenafil is also marketed as VIAGRA. The safety and efficacy of combinations of REVATIO with VIAGRA or other PDE-5 inhibitors have not been studied. Inform patients taking REVATIO not to take VIAGRA or other PDE-5 inhibitors."
How long the effect is documented to lastA duration is an answer to a question only one of the two labels is asking. The 4-hour figure describes a window for sexual activity and says nothing about how long sildenafil is in the body — the terminal half-life on both labels is about 4 hours, which is a different measurement again.	up to 4 hours — and the label adds that it was already weaker by then: "The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours." (section 12.2 Pharmacodynamics).	The Revatio label states no duration of effect at all. Its endpoints are exercise ability and delay of clinical worsening, measured over weeks, so there is no "how long does it last" figure to read across.
Which tablet strengths existA 20 mg sildenafil tablet in a pill organiser is almost certainly a pulmonary prescription, not a low-dose Viagra. Nothing on the Viagra label describes a 20 mg dose, and nothing on the Revatio label describes taking one before sexual activity.	25 / 50 / 100 mg, all three within the approved as-needed range of 25–100 mg.	Revatio is one strength, 20 mg, a white round tablet engraved RVT20 — below the lowest Viagra strength and intended to be taken three times a day rather than once.

Viagra tablets

Dosage form: Tablet, film coated
Route: Oral, as needed before sexual activity
Marketing category: NDA — NDA020895
Label read: SPL version 32, effective December 15, 2017

What this product is approved to treat

—VIAGRA is indicated for the treatment of erectile dysfunction.

The labelled ladder

When	Dose	What the label attaches to this step
Most patients	50 mg as needed	For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. The label also permits a wide window: VIAGRA may be taken anywhere from 30 minutes to 4 hours before sexual activity. Section 2.1 Dosage Information.
If increased	100 mg as needed	Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. This is a change of dose, not a step on a schedule — nothing on this label escalates with time.
If decreased	25 mg as needed	The same sentence permits the reduction. The label gives no criterion beyond "effectiveness and toleration", and no minimum time at any dose.
On an alpha-blocker	25 mg to start	When VIAGRA is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating VIAGRA treatment and VIAGRA should be initiated at 25 mg (section 2.3 Dosage Adjustments in Specific Situations). Section 7.2 of the same label words it as "VIAGRA should be initiated at the lowest dose" without naming 25 mg. The dosage section is the more specific of the two and is what this chart prints.
On ritonavir	25 mg per 48 hours	The label states: "The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold." This is the one place the once-per-day ceiling is replaced by a once-per-two-days one.
Over 65, or liver or severe kidney impairment	25 mg to start	The label states: "Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance <30 mL/minute) because administration of VIAGRA in these patients resulted in higher plasma levels of sildenafil." The REVATIO label says the opposite about kidneys — see the divergence table.

Ceiling. 100 mg, and only once in a day: "Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg", with "The maximum recommended dosing frequency is once per day." Both halves are brand facts. The REVATIO label permits 20 mg three times a day titrated to 80 mg three times a day in adults, which is a daily total this label has no equivalent of.

How it is supplied

Presentation	Total strength	Concentration	Delivers
Blue, film-coated, rounded-diamond-shaped tablet	25 mg	Not applicable — a solid oral dose form has no concentration	One tablet, debossed PFIZER on one side and VGR25 on the other
Blue, film-coated, rounded-diamond-shaped tablet	50 mg	Not applicable — a solid oral dose form has no concentration	One tablet, debossed PFIZER on one side and VGR50 on the other
Blue, film-coated, rounded-diamond-shaped tablet	100 mg	Not applicable — a solid oral dose form has no concentration	One tablet, debossed PFIZER on one side and VGR100 on the other

Administration, as the label words it

—For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity.
—VIAGRA may be taken with or without food. A high-fat meal delays the peak by about an hour and reduces it by 29%, the largest food effect of the four oral PDE5 inhibitors.
—Concomitant use with organic nitrates or nitric oxide donors in any form is an absolute contraindication, not a caution. The label refuses to name a safe interval: "After patients have taken VIAGRA, it is unknown when nitrates, if necessary, can be safely administered."
—Do not use VIAGRA in patients who are using a GC stimulator, such as riociguat. PDE5 inhibitors, including VIAGRA, may potentiate the hypotensive effects of GC stimulators.
—Physicians should inform patients not to take VIAGRA with other PDE5 inhibitors including REVATIO or other pulmonary arterial hypertension (PAH) treatments containing sildenafil.

Storage

Tablets: Store at 25 °C (77 °F); excursions permitted to 15–30 °C (59–86 °F). No refrigeration, no in-use clock.; Until the expiration date on the bottle

Children and adolescents

VIAGRA is not indicated for use in pediatric patients. Safety and effectiveness have not been established in pediatric patients.

This statement belongs to Viagra tablets. It is not a statement about sildenafil, and another brand of the same molecule may say the opposite.

The same molecule under other brand names

Everything below is sildenafil. None of it is Viagra, and a dose from one column carried into another is not a smaller or larger version of the same instruction — it is a different product’s schedule.

Brand	Form	Approved for	Ladder	Maximum
Revatio	Oral tablet, oral suspension and intravenous injection — three times a day	Pulmonary arterial hypertension (WHO Group I) in adults, to improve exercise ability and delay clinical worsening; and in pediatric patients 1 to 17 years old	20 mg three times a day → up to 80 mg three times a day in adults	80 mg three times a day in adults; no maximum identified in paediatric patients, with titration to 40 mg three times a day above 45 kg

Switching between products

The two sildenafil brands are not alternatives to each other

The safety and efficacy of combinations of VIAGRA with other PDE5 Inhibitors, including REVATIO or other pulmonary arterial hypertension (PAH) treatments containing sildenafil, or other treatments for erectile dysfunction have not been studied. Such combinations may further lower blood pressure. Therefore, the use of such combinations is not recommended.

Viagra and Revatio

Nitrates are an absolute contraindication, and the label will not name a safe gap

After patients have taken VIAGRA, it is unknown when nitrates, if necessary, can be safely administered. Although plasma levels of sildenafil at 24 hours post dose are much lower than at peak concentration, it is unknown whether nitrates can be safely co-administered at this time point.

Viagra

What this page does not tell you

Price — list, cash or copay: No price appears anywhere on this page, and no price is emitted in its structured data. Sildenafil is sold as a brand, as an authorised generic and as dozens of generics at rates that differ by pharmacy, by quantity and by discount card, and we could not find a source for a current US figure that we could cite and re-verify the way every other number here is cited. A stale or wrong price is the most consequential thing a page like this could print, so the field is absent rather than estimated.
How long you must wait after a dose before a nitrate is safe: The Viagra label refuses to answer, and so does this page. Its words are "it is unknown when nitrates, if necessary, can be safely administered", and it explicitly declines to endorse the 24-hour point. That refusal must not be filled in with the 48 hours the tadalafil label names or the 12 hours the avanafil label names — those are different molecules with different half-lives, and none of the three says a nitrate is ever safe alongside a dose.
An onset of action: The string "onset of action" does not appear on this label. What it gives is a lead time — take it approximately 1 hour before, anywhere from 30 minutes to 4 hours before — and a time to peak plasma concentration of 30 to 120 minutes, median 60. A lead time is an instruction and a Tmax is a measurement; neither is an onset, and printing one as though the label stated it would be attributing a figure to a document that does not contain it.
How well it works, as a percentage: Response rates for erectile dysfunction depend on the cause, the severity, the instrument used to measure it and the population enrolled, and the figures circulating for Viagra are drawn from trials with different answers to all four. The label reports its own studies in section 14 with their populations attached; a single headline percentage detached from them would be less true than saying nothing.

Frequently asked questions

What is the maximum dose of Viagra?: 100 mg, once in a day. The label pairs two sentences: "Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg" and "The maximum recommended dosing frequency is once per day." Both are facts about this brand. The same molecule as Revatio is 20 mg three times a day, titratable to 80 mg three times a day, so a sildenafil ceiling quoted without a brand name means nothing.
Is Revatio the same as Viagra?: Same molecule, different products. Revatio is sildenafil for pulmonary arterial hypertension in adults and in children from one year old, given as a 20 mg tablet three times a day, as a 10 mg/mL oral suspension, or as a 10 mg/12.5 mL intravenous injection. Viagra is sildenafil for erectile dysfunction, 25, 50 or 100 mg, at most once a day. Each label tells the patient not to take the other.
How long before sex should Viagra be taken?: The label's instruction is "approximately 1 hour before sexual activity", with a permitted window: "However, VIAGRA may be taken anywhere from 30 minutes to 4 hours before sexual activity." Peak plasma concentration is reached in 30 to 120 minutes, median 60 minutes, in the fasted state. A high-fat meal pushes the peak back a full hour and cuts it by 29%, the largest food effect of the four oral PDE5 inhibitors.
How long does Viagra last?: The label documents effect up to 4 hours, and says in the same sentence that it was already fading: "The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours." That is a window for activity, not a measure of how long the drug is in the body — sildenafil and its active metabolite both have terminal half-lives of about 4 hours.
Does a starting dose change with age or kidney function?: On this label, yes: "Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance <30 mL/minute)." On the Revatio label for the same molecule, no: it states that no dose adjustment is required, including for severe impairment below 30 mL/min. Two labels, one drug, opposite instructions — because the dose sizes and frequencies being corrected are different.
Can Viagra be taken with nitrates?: No. It is an absolute contraindication on this label, not a caution: sildenafil "was shown to potentiate the hypotensive effects of nitrates, and its administration to patients who are using nitric oxide donors such as organic nitrates or organic nitrites in any form either regularly and/or intermittently is therefore contraindicated." That covers nitroglycerin, isosorbide, and amyl or butyl nitrite "poppers". The label also declines to say when a nitrate becomes safe afterwards, which is not the same as saying no wait is needed.
Why does the dose drop to 25 mg with ritonavir?: Because the interaction is eleven-fold. The label states: "The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold." That is the only circumstance in which this label replaces the once-per-day ceiling with a once-per-48-hours one. Strong CYP3A4 inhibitors such as ketoconazole, itraconazole or erythromycin get a 25 mg starting dose without the 48-hour rule.
Is there a Viagra tablet smaller than 25 mg?: Not under this brand. Section 3 lists three strengths only — 25 mg, 50 mg and 100 mg — as blue, film-coated, rounded-diamond-shaped tablets debossed VGR25, VGR50 or VGR100. A 20 mg sildenafil tablet exists, but it is the Revatio strength, a white round tablet engraved RVT20 intended to be taken three times a day for a lung condition.

Sources

Next steps

Compare online ED providersWho prescribes branded sildenafil, who prescribes generic, and what each one asks for before they will.Work out when to take itEnter a time and see the labelled dosing window for each of the four PDE5 inhibitors, with the basis for every figure named.

Other brands

Educational reference, not medical advice. Sildenafil is a prescription-only medicine and its use with nitrates in any form is an absolute contraindication. This page reports what two FDA labels state; it does not recommend a dose.