Non-peptide
Sildenafil
Sildenafil is FDA-approved as Viagra for erectile dysfunction and as Revatio for high blood pressure in the lungs. For those uses the evidence grade is strong-human. Taken with nitrate heart drugs, it can drop blood pressure to dangerous levels. FDA keeps finding it hidden in sexual enhancement products.
This page has not been individually reviewed by a clinician.
Fact sheet · 6 facts
every row cites its source and its date| Fact | Value | Tier | Checked | Source |
|---|---|---|---|---|
| Also called | Viagra, Revatio, sildenafil citrate | primary | accessdata.fda.gov | |
| Class | non-peptide | primary | accessdata.fda.gov | |
| Regulatory status | fda-approved | primary | accessdata.fda.gov | |
| Status source read | 2026-10-26 | primary | accessdata.fda.gov | |
| Evidence grade | strong-human | our assessment | peptideindex.ai | |
| Label dosing | From the Viagra and Revatio labels. For erectile dysfunction, most men take 50 mg about 1 hour before sex, as needed, no more than once a day. The dose may go up to 100 mg or down to 25 mg. For high blood pressure in the lungs, adults take 20 mg by mouth three times a day, which may be raised to 80 mg three times a day. Adults may instead get 10 mg as a shot into a vein three times a day. Children 1 to 17 years old take 10 mg or 20 mg three times a day, by weight. The prescriber sets the dose. | primary | accessdata.fda.gov |
Short answer
Sildenafil is FDA-approved as Viagra for erectile dysfunction and as Revatio for high blood pressure in the lungs. For those uses the evidence grade is strong-human. Taken with nitrate heart drugs, it can drop blood pressure to dangerous levels. FDA keeps finding it hidden in sexual enhancement products.
Our assessment, drawn from the sources below.
What it is
Sildenafil is a drug that blocks an enzyme called PDE5 [1] [2]. This relaxes the muscle in blood vessel walls [2]. It is not a peptide.
As Viagra, it is a tablet for erectile dysfunction, which means trouble getting or keeping an erection [1]. As Revatio, it treats high blood pressure in the arteries of the lungs, called pulmonary arterial hypertension [2]. Revatio comes as a tablet, a liquid and a shot [2]. FDA first approved sildenafil in 1998 [1] [3].
Where it stands legally
Sildenafil is FDA-approved: Drugs@FDA lists Viagra for erectile dysfunction and Revatio for high blood pressure in the lungs as approved prescription drugs [3] [4]. The approval is for use under a prescriber's care [7]. It does not make a product sold as a supplement legal when that product hides sildenafil [9]. Checked 26 October 2026.
FDA says a product with undeclared sildenafil is a misbranded drug [9]. FDA also says a compounded copy is not FDA-approved. In 2025, it warned that calling a compounded copy a generic Viagra is false or misleading [10] [18].
Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug [5]. Sildenafil is not on FDA's 503A category list [6].
What the evidence shows
Evidence grade: strong-human · our assessment
The evidence grade is strong-human for its two approved uses [11] [12] [14]. In a 1998 trial in men with erectile dysfunction, 69% of tries at sex succeeded on sildenafil [11]. On a dummy pill, 22% did [11]. A 2009 review of many trials found this class of drug helped erections more than a dummy pill [14]. It found no clear difference between sildenafil, vardenafil and tadalafil [14].
In a 2005 trial, 278 adults with high blood pressure in the lungs took sildenafil or a dummy pill for 12 weeks [12]. Those on sildenafil walked about 45 to 50 meters farther in six minutes [12]. In a 2012 trial of 235 children, the result for all doses together was only borderline [13]. Medium and high doses did better than a dummy pill [13].
In a 2022 study in rats with high blood pressure in the lungs, adding a diabetes drug did no better than sildenafil alone [17].
Known risks
- Taken with nitrate heart drugs, such as nitroglycerin, it can drop blood pressure to dangerous levels. Both labels say never to combine them [1] [2].
- Both labels also say not to take it with riociguat, a drug for high blood pressure in the lungs [1] [2].
- Sudden loss of sight in one or both eyes has been reported rarely. It can be a sign of damage to the nerve of the eye, called NAION [1] [15].
- Sudden loss of hearing has been reported. The labels say to get medical care right away if it happens [1] [2].
- An erection that lasts more than 4 hours needs emergency care [1].
- Taken with alpha-blockers or other blood pressure drugs, it can lower blood pressure too far [1].
- In a long study of children with high blood pressure in the lungs, more children died on higher doses. The Revatio label says the deaths came from the disease getting worse [2] [13].
- In people whose lung disease comes from sickle cell disease, Revatio may cause serious pain crises [2].
- In the label's studies, the most common problems were headache, flushing and upset stomach [1] [11].
- Products sold as supplements may hold hidden sildenafil. A person on nitrates may take it without knowing [7] [9].
What nobody knows yet
- In the 2009 review, many trials were short and of low quality. Long-term benefits and harms are less clear [14].
- Nobody knows for sure if the drug itself causes NAION. The 2015 study was observational, so it shows a link, not proof of cause [15].
- The best dose for children is not settled. The 2012 trial called for more study of dosing by age and weight [13].
- It is not known if sildenafil helps people with scleroderma whose lung pressure is only a little high. A US trial is testing it [20].
- Nobody can say which products sold as supplements hide sildenafil. FDA says it cannot test every such product [7].
Legitimate ways to get it
The legal way to get sildenafil is a prescription [1] [2]. Viagra is approved for erectile dysfunction, and Revatio for high blood pressure in the lungs [3] [4].
Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug [5]. A compounded copy is not FDA-approved [10].
US trials of sildenafil are open, such as one in people with scleroderma [20] and one in newborns with a hole in the diaphragm, the muscle under the lungs [21]. The trials block on this page lists open trials with their dates.
Approved product
Approved by FDA as a prescription tablet for erectile dysfunction.
Brand names: Viagra
Manufacturer: Viatris
Indication: Treatment of erectile dysfunction.
Approved product
Approved by FDA as a prescription tablet, liquid and shot for high blood pressure in the lungs.
Brand names: Revatio
Manufacturer: Viatris
Indication: Treatment of pulmonary arterial hypertension (WHO Group I) in adults, and in children 1 to 17 years old.
Lawful compounding
Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug.
Recruiting trials
A listing is not a recommendation. Trials have strict eligibility rules. Talk to your doctor and read the official record.
Snapshot of .clinicaltrials.gov
NCT06800092
Sildenafil to Prevent and Reduce Cancer Related Cognitive Impairment
Phase: Phase 2/Phase 3 · Sponsor: The University of Texas Medical Branch, Galveston · Status: Not yet recruiting
Countries: United States
US states: Texas
NCT07039760
Asciminib With or Without Sildenafil for Brain Tumors
Phase: Early phase 1 · Sponsor: Washington University School of Medicine · Status: Not yet recruiting
Countries: United States
US states: Missouri
NCT07647003
A Study to Evaluate the Effect of Two Fixed-Dose Leucine, Sildenafil and Metformin Combinations on Blood Pressure in Individuals With Hypertension
Phase: Phase 2 · Sponsor: NuSirt Biopharma · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT06810284
Sildenafil Plus Hypothermia to Treat Neonatal Encephalopathy
Phase: Phase 2 · Sponsor: Assistance Publique - Hôpitaux de Paris · Status: Not yet recruiting
Countries: France
US states: none listed
NCT07508358
Vaginal Sildenafil for Primary Dysmenorrhea
Phase: Phase 1 · Sponsor: Kevin Hellman · Status: Not yet recruiting
Countries: United States
US states: Illinois
NCT07824674
The Effect of Additive On-Demand Sildenafil vs. Dextrose Candy on Maximum Exercise Capacity in Pulmonary Arterial Hypertension
Phase: Phase 2/Phase 3 · Sponsor: Silvia Ulrich · Status: Recruiting
Countries: Switzerland
US states: none listed
NCT07732387
A Study to Assess the Safety, Tolerability and Pharmacokinetics of Viaca (Sildenafil + Cabergoline) Compared With Sildenafil and Cabergoline
Phase: Phase 1 · Sponsor: Yanping Kong · Status: Not yet recruiting
Countries: Australia
US states: none listed
NCT07713914
Randomized Study of Triple Therapy vs Sildenafil Dose Optimization in Pulmonary Arterial Hypertension
Phase: Phase 4 · Sponsor: University of Sao Paulo General Hospital · Status: Recruiting
Countries: Brazil
US states: none listed
NCT07536880
Effect of Sildenafil on Left Ventricular Function in Pediatric With Primary Dilated Cardiomyopathy
Phase: Not stated · Sponsor: Assiut University · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT07601646
A Single-Arm, Dose Escalation of an Intraurethral Alprostadil Paste for Erectile Dysfunction
Phase: Phase 2 · Sponsor: Ryan Flannigan, MD · Status: Recruiting
Countries: Canada
US states: none listed
NCT07290400
Effect of Moderate Alcohol on Absorption and Onset of Hezkue Sildenafil Suspension
Phase: Phase 2 · Sponsor: Aspargo Labs, Inc · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT07302698
PK and Onset of Hezkue Oral Sildenafil Suspension After Alcohol Consumption
Phase: Phase 1 · Sponsor: Aspargo Labs, Inc · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT07117383
Hezkue®, Hezkue Turbo®, and Commercial Sildenafil Products in Fed Healthy Male Subject
Phase: Phase 1 · Sponsor: Aspargo Labs, Inc · Status: Not yet recruiting
Countries: United States
US states: New York
NCT07231185
Phase 2 Efficacy Study of Sildenafil Products in Adult Men With Erectile Dysfunction
Phase: Phase 2 · Sponsor: Aspargo Labs, Inc · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT07391579
Daily Tadalafil 5 mg Combined With On-Demand Sildenafil 100 mg for Treatment of Erectile Dysfunction in PDE-5I Non Responder Patients
Phase: Phase 4 · Sponsor: Mansoura University · Status: Recruiting
Countries: Egypt
US states: none listed
NCT07177326
Combination Therapy of Tadalafil 2.5mg Plus Sildenafil 25mg Versus Tadalafil 5 mg Monotherapy for Treatment of Erectile Dysfunction: A Randomized, Placebo-Controlled Double-Blinded Cross-Over Study
Phase: Phase 3 · Sponsor: Assiut University · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT06123156
Interest of Early Erectile Rehabilitation With Sildenafil After Radiotherapy and Proctectomy for Rectal Cancer
Phase: Phase 3 · Sponsor: University Hospital, Rouen · Status: Recruiting
Countries: France
US states: none listed
NCT07057011
Therapeutic Outcomes of Selective Serotonin Reuptake Inhibitors and Phosphodiesterase-5 Inhibitors Combination Therapy Versus Monotherapy
Phase: Not applicable · Sponsor: South Valley University · Status: Not yet recruiting
Countries: Egypt
US states: none listed
NCT06839651
Umbilical Cord Mesenchymal Stem Cell Secretome in Severe Erectile Dysfunction Non-responsive to Sildenafil
Phase: Phase 1 · Sponsor: Universitas Indonesia · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT06872866
The Objective of This Phase 1 Study is to Evaluate the Food Effect of 100 mg Hezkue Turbo® (ASP-001.1, Sildenafil) Under Fed Versus 100 mg of Hezkue Turbo® (ASP-001.1, Sildenafil) Under Fasted Conditions in Healthy Adult Male Subjects
Phase: Phase 1 · Sponsor: Aspargo Labs, Inc · Status: Recruiting
Countries: United States
US states: New York
NCT06510322
Sildenafil to Reduce Vascular Remodeling During Left Ventricular Assist Device Support
Phase: Early phase 1 · Sponsor: Montefiore Medical Center · Status: Recruiting
Countries: United States
US states: New York
NCT06797479
Detection of Circulating Therapeutic Monoclonal Antibodies in Biological Samples of Gynecological Cancer Patients.
Phase: Not stated · Sponsor: Fondazione Policlinico Universitario Agostino Gemelli IRCCS · Status: Not yet recruiting
Countries: none listed
US states: none listed
NCT06954597
Safety and Tolerability of TOP-N53 Applied on Digital Ulcers in Patients With Systemic Sclerosis
Phase: Phase 2 · Sponsor: Topadur Pharma AG · Status: Recruiting
Countries: France, Switzerland
US states: none listed
NCT06782659
Study to Compare the Effects of Viagra® Vs Hezkue® in Healthy Fasted Male Participants.
Phase: Phase 1 · Sponsor: Aspargo Labs, Inc · Status: Not yet recruiting
Countries: United States
US states: Florida
NCT06753981
Efficacy and Safety of Triple-targeted Drug Therapy in Treatment-naive Patients With Non-low-risk PAH: A Real-world, Multicenter Study
Phase: Not stated · Sponsor: Qianfoshan Hospital · Status: Recruiting
Countries: China
US states: none listed
NCT06715280
Switching of Sildenafil to Riociguat in CTEPH Patients
Phase: Phase 4 · Sponsor: Chinese University of Hong Kong · Status: Recruiting
Countries: Hong Kong
US states: none listed
NCT05782244
Sildenafil for Microvasculopathy in Chronic TBI
Phase: Phase 2 · Sponsor: University of Pennsylvania · Status: Recruiting
Countries: United States
US states: Pennsylvania
NCT06098833
Treatment of Neonatal Encephalopathy With Oral Sildenafil Suspension to Repair Brain Injury Secondary to Birth Asphyxia
Phase: Phase 2 · Sponsor: Pia Wintermark · Status: Recruiting
Countries: United States, Canada
US states: Colorado
NCT06324396
IMProving DRug Dosing and Outcomes for Single VEntricle Patients With Fontan Associated Liver Disease
Phase: Phase 1 · Sponsor: Children's Mercy Hospital Kansas City · Status: Recruiting
Countries: United States
US states: Missouri
NCT06875258
PEnile ReHABilitation After Nerve Sparing Robot-assisted Radical Prostatectomy for Prostate Cancer 2.0 (PEHAB-II)
Phase: Phase 4 · Sponsor: The Netherlands Cancer Institute · Status: Recruiting
Countries: Netherlands
US states: none listed
NCT06317805
Initial Triple Therapy Including Parenteral Treprostinil vs Initial Double Oral Therapy in PAH Group I Patients
Phase: Phase 4 · Sponsor: AOP Orphan Pharmaceuticals AG · Status: Recruiting
Countries: Austria, Czechia, France, Germany, Hungary, Italy, Poland, Portugal, Romania, Spain
US states: none listed
NCT05201144
A Trial of Phosphodiesterase-5 Inhibitor in Neonatal Congenital Diaphragmatic Hernia (TOP-CDH)
Phase: Phase 2 · Sponsor: University of Utah · Status: Recruiting
Countries: United States
US states: Utah
NCT05061368
Oral Sildenafil for Exercise Capacity, Dyspnea and Cardiopulmonary Function in COPD
Phase: Phase 2 · Sponsor: University of Alberta · Status: Recruiting
Countries: Canada
US states: none listed
NCT04797286
Sildenafil for Early Pulmonary Vascular Disease in Scleroderma
Phase: Phase 2 · Sponsor: Johns Hopkins University · Status: Recruiting
Countries: United States
US states: Louisiana, Maryland
NCT04898114
Nebulized Magnesium Sulfate and Sildenafil for Persistent Pulmonary Hypertension of Newborn
Phase: Phase 1/Phase 2 · Sponsor: Sohag University · Status: Recruiting
Countries: Egypt
US states: none listed
NCT07377084
Metabolomics of Cancers of the Upper Aerodigestive Tract
Phase: Not stated · Sponsor: Centre Antoine Lacassagne · Status: Recruiting
Countries: France
US states: none listed
NCT01347216
COMPERA / COMPERA-KIDS
Phase: Not stated · Sponsor: Technische Universität Dresden · Status: Recruiting
Countries: Belgium, Germany, Italy, Switzerland
US states: none listed
How people are getting it anyway
This section describes what happens and is not a recommendation.
Two ways of getting sildenafil other than an approved, prescribed product show up in FDA's records [7] [10]. The first is products sold as supplements for sexual enhancement with sildenafil hidden inside. FDA lab tests found it in such products in 2020, 2021 and 2026, and their labels did not list it [7] [8]. A 2018 study of FDA warnings found sildenafil was the most common hidden drug in these products [16] [19]. FDA warns the hidden drug can react with nitrates and drop blood pressure to dangerous levels [7] [8].
The second is websites that sell compounded sildenafil and call it a generic Viagra [10] [18]. FDA says a compounded copy is not FDA-approved, and that such claims are false or misleading [10].
Counterfeit or diverted
Products sold as dietary supplements for sexual enhancement with sildenafil hidden inside and not listed on the label.
The lawFDA says a product with undeclared sildenafil is a misbranded drug, because its label hides the drug and gives no warnings.fda.gov
Documented riskFDA warns the hidden drug can react with nitrates, such as nitroglycerin, and lower blood pressure to dangerous levels.fda.gov
Documented riskFDA says it cannot test every product sold as a supplement for hidden drugs.fda.gov
Documented riskFrom 2007 to 2016, sildenafil was the most common hidden drug in sexual enhancement supplements named in FDA warnings.pubmed.ncbi.nlm.nih.gov
Enforcement FDA warning letter to a distributor whose product sold as a supplement held undeclared sildenafil.fda.gov
Enforcement FDA told consumers not to buy or use a sexual enhancement supplement that its lab found to hold hidden sildenafil and tadalafil.fda.gov
Enforcement FDA again told consumers not to buy or use a line of sexual enhancement products its lab found to hold hidden sildenafil and tadalafil.fda.gov
Telehealth
Websites that sell compounded sildenafil to consumers and call it a generic Viagra.
The lawFDA says a compounded drug is not FDA-approved, and a claim that it is the same as an approved drug is false or misleading.fda.gov
Documented riskFDA says such claims imply the copy is the same as the approved drug when it is not.fda.gov
Enforcement FDA warning letter to a website that sold compounded sildenafil and called it a generic Viagra.fda.gov
Sources
- [1]Viagra (sildenafil citrate) tablets label, revised August 2017Label · primary
- [2]Revatio (sildenafil) tablets, oral suspension and injection label, revised December 2024Label · primary
- [3]Drugs@FDA: Viagra (sildenafil citrate) tablets, application 020895Regulatory · primary
- [4]Drugs@FDA: Revatio (sildenafil citrate) tablets, application 021845Regulatory · primary
- [5]FDA: bulk drug substances used in compounding under section 503ARegulatory · primary
- [6]FDA: 503A bulk drug substances category list, updated May 2026Regulatory · primary
- [7]FDA health fraud notice: sexual enhancement supplement with hidden sildenafil and tadalafil, 29 May 2026Regulatory · primary
- [8]FDA health fraud notice: sexual enhancement products with hidden sildenafil, 2020 to 2026Regulatory · primary
- [9]FDA warning letter on a product sold as a supplement with undeclared sildenafil, 28 August 2018Regulatory · primary
- [10]FDA warning letter on claims that compounded sildenafil is a generic Viagra, 9 September 2025Regulatory · primary
- [11]Randomized trial: oral sildenafil for erectile dysfunction, 1998Rct · peer-reviewed
- [12]Randomized trial: sildenafil for pulmonary arterial hypertension in adults, 2005Rct · peer-reviewed
- [13]Randomized dose-ranging trial: oral sildenafil in children with pulmonary arterial hypertension, 2012Rct · peer-reviewed
- [14]Systematic review: PDE5 inhibitors and hormone treatments for erectile dysfunction, 2009Systematic review · peer-reviewed
- [15]Case-crossover study: sudden optic nerve damage (NAION) and PDE5 inhibitor use, 2015Human trial · peer-reviewed
- [16]Study: unapproved drug ingredients in dietary supplements named in FDA warnings, 2007 to 2016Reference · peer-reviewed
- [17]Rat study: dapagliflozin and sildenafil in pulmonary arterial hypertension, 2022Animal · peer-reviewed
- [18]National Law Review: FDA's focus returns to compounding and telehealthLegal analysis · legal-analysis
- [19]CBS News: many dietary supplements contain unapproved, dangerous ingredients, October 2018Reference · established-news
- [20]ClinicalTrials.gov NCT04797286: sildenafil for early pulmonary vascular disease in sclerodermaReference · primary
- [21]ClinicalTrials.gov NCT05201144: sildenafil in newborns with congenital diaphragmatic herniaReference · primary
Last verified · 6 facts · 8 sources
- clinicaltrials.gov
- peptideindex.ai
- peptideindex.ai
- pubmed.ncbi.nlm.nih.gov
- pubmed.ncbi.nlm.nih.gov
- accessdata.fda.gov
- accessdata.fda.gov
- fda.gov
Primary source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895
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Information, not medical advice.
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