# 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.

Status checked: 2026-10-26. Last verified: 2026-10-26. Primary source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895

This page has not been individually reviewed by a clinician.

Information, not medical advice.

| Fact | Value | Tier | Checked | Source |
|---|---|---|---|---|
| Also called | Viagra, Revatio, sildenafil citrate | primary | 2026-10-26 | [source](https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf) |
| Class | non-peptide | primary | 2026-10-26 | [source](https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf) |
| Regulatory status | fda-approved | primary | 2026-10-26 | [source](https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895) |
| Status source read | 2026-10-26 | primary | 2026-10-26 | [source](https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895) |
| Evidence grade | strong-human | our assessment | 2026-10-26 | [source](https://peptideindex.ai/methodology#evidence-grade) |
| 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 | 2026-10-26 | [source](https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf) |

## Name

Sildenafil

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

## Summary

A prescription drug for erectile dysfunction, sold as Viagra, and for high blood pressure in the lungs, sold as Revatio.

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

## 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.

Source: https://peptideindex.ai/methodology#short-answer

## 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].

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

## 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].

Source: https://pubmed.ncbi.nlm.nih.gov/19884626/

## 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].

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

## 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].

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895

## What the evidence shows

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].

Source: https://pubmed.ncbi.nlm.nih.gov/16291984/

## 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.

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

## 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].

Source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients

## Access routes

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895

### Approved product

Detail: Approved by FDA as a prescription tablet for erectile dysfunction.

Brand names: Viagra

Manufacturer: Viatris

Indication: Treatment of erectile dysfunction.

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895

### Approved product

Detail: 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.

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021845

### Lawful compounding

Detail: Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug.

Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act

## Unofficial channels

Source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients

### Counterfeit or diverted

What it is: Products sold as dietary supplements for sexual enhancement with sildenafil hidden inside and not listed on the label.

Legal position: FDA says a product with undeclared sildenafil is a misbranded drug, because its label hides the drug and gives no warnings. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/duy-drugs-inc-542933-08282018)

Documented risks:

- FDA warns the hidden drug can react with nitrates, such as nitroglycerin, and lower blood pressure to dangerous levels. (source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients)
- FDA says it cannot test every product sold as a supplement for hidden drugs. (source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients)
- From 2007 to 2016, sildenafil was the most common hidden drug in sexual enhancement supplements named in FDA warnings. (source: https://pubmed.ncbi.nlm.nih.gov/30646238/)

Enforcement:

- 2018-08-28: FDA warning letter to a distributor whose product sold as a supplement held undeclared sildenafil. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/duy-drugs-inc-542933-08282018)
- 2026-05-29: FDA told consumers not to buy or use a sexual enhancement supplement that its lab found to hold hidden sildenafil and tadalafil. (source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients)
- 2026-07-01: FDA again told consumers not to buy or use a line of sexual enhancement products its lab found to hold hidden sildenafil and tadalafil. (source: https://www.fda.gov/drugs/medication-health-fraud-notifications/magnum-brand-products-may-be-harmful-due-hidden-drug-ingredients)

Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/duy-drugs-inc-542933-08282018

### Telehealth

What it is: Websites that sell compounded sildenafil to consumers and call it a generic Viagra.

Legal position: FDA says a compounded drug is not FDA-approved, and a claim that it is the same as an approved drug is false or misleading. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025)

Documented risks:

- FDA says such claims imply the copy is the same as the approved drug when it is not. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025)

Enforcement:

- 2025-09-09: FDA warning letter to a website that sold compounded sildenafil and called it a generic Viagra. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025)

Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025

## Recruiting trials

Snapshot date: 2026-10-26.

A listing is not a recommendation. Trials have strict eligibility rules. Talk to your doctor and read the official record.

- nct NCT06800092, url https://clinicaltrials.gov/study/NCT06800092, phase Phase 2/Phase 3, title Sildenafil to Prevent and Reduce Cancer Related Cognitive Impairment, status not-yet-recruiting, sponsor The University of Texas Medical Branch, Galveston, countries United States, us states Texas
- nct NCT07039760, url https://clinicaltrials.gov/study/NCT07039760, phase Early phase 1, title Asciminib With or Without Sildenafil for Brain Tumors, status not-yet-recruiting, sponsor Washington University School of Medicine, countries United States, us states Missouri
- nct NCT07647003, url https://clinicaltrials.gov/study/NCT07647003, phase Phase 2, title A Study to Evaluate the Effect of Two Fixed-Dose Leucine, Sildenafil and Metformin Combinations on Blood Pressure in Individuals With Hypertension, status not-yet-recruiting, sponsor NuSirt Biopharma, countries none listed, us states none listed
- nct NCT06810284, url https://clinicaltrials.gov/study/NCT06810284, phase Phase 2, title Sildenafil Plus Hypothermia to Treat Neonatal Encephalopathy, status not-yet-recruiting, sponsor Assistance Publique - Hôpitaux de Paris, countries France, us states none listed
- nct NCT07508358, url https://clinicaltrials.gov/study/NCT07508358, phase Phase 1, title Vaginal Sildenafil for Primary Dysmenorrhea, status not-yet-recruiting, sponsor Kevin Hellman, countries United States, us states Illinois
- nct NCT07824674, url https://clinicaltrials.gov/study/NCT07824674, phase Phase 2/Phase 3, title The Effect of Additive On-Demand Sildenafil vs. Dextrose Candy on Maximum Exercise Capacity in Pulmonary Arterial Hypertension, status recruiting, sponsor Silvia Ulrich, countries Switzerland, us states none listed
- nct NCT07732387, url https://clinicaltrials.gov/study/NCT07732387, phase Phase 1, title A Study to Assess the Safety, Tolerability and Pharmacokinetics of Viaca (Sildenafil + Cabergoline) Compared With Sildenafil and Cabergoline, status not-yet-recruiting, sponsor Yanping Kong, countries Australia, us states none listed
- nct NCT07713914, url https://clinicaltrials.gov/study/NCT07713914, phase Phase 4, title Randomized Study of Triple Therapy vs Sildenafil Dose Optimization in Pulmonary Arterial Hypertension, status recruiting, sponsor University of Sao Paulo General Hospital, countries Brazil, us states none listed
- nct NCT07536880, url https://clinicaltrials.gov/study/NCT07536880, phase Not stated, title Effect of Sildenafil on Left Ventricular Function in Pediatric With Primary Dilated Cardiomyopathy, status not-yet-recruiting, sponsor Assiut University, countries none listed, us states none listed
- nct NCT07601646, url https://clinicaltrials.gov/study/NCT07601646, phase Phase 2, title A Single-Arm, Dose Escalation of an Intraurethral Alprostadil Paste for Erectile Dysfunction, status recruiting, sponsor Ryan Flannigan, MD, countries Canada, us states none listed
- nct NCT07290400, url https://clinicaltrials.gov/study/NCT07290400, phase Phase 2, title Effect of Moderate Alcohol on Absorption and Onset of Hezkue Sildenafil Suspension, status not-yet-recruiting, sponsor Aspargo Labs, Inc, countries none listed, us states none listed
- nct NCT07302698, url https://clinicaltrials.gov/study/NCT07302698, phase Phase 1, title PK and Onset of Hezkue Oral Sildenafil Suspension After Alcohol Consumption, status not-yet-recruiting, sponsor Aspargo Labs, Inc, countries none listed, us states none listed
- nct NCT07117383, url https://clinicaltrials.gov/study/NCT07117383, phase Phase 1, title Hezkue®, Hezkue Turbo®, and Commercial Sildenafil Products in Fed Healthy Male Subject, status not-yet-recruiting, sponsor Aspargo Labs, Inc, countries United States, us states New York
- nct NCT07231185, url https://clinicaltrials.gov/study/NCT07231185, phase Phase 2, title Phase 2 Efficacy Study of Sildenafil Products in Adult Men With Erectile Dysfunction, status not-yet-recruiting, sponsor Aspargo Labs, Inc, countries none listed, us states none listed
- nct NCT07391579, url https://clinicaltrials.gov/study/NCT07391579, phase Phase 4, title Daily Tadalafil 5 mg Combined With On-Demand Sildenafil 100 mg for Treatment of Erectile Dysfunction in PDE-5I Non Responder Patients, status recruiting, sponsor Mansoura University, countries Egypt, us states none listed
- nct NCT07177326, url https://clinicaltrials.gov/study/NCT07177326, phase Phase 3, title 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, status not-yet-recruiting, sponsor Assiut University, countries none listed, us states none listed
- nct NCT06123156, url https://clinicaltrials.gov/study/NCT06123156, phase Phase 3, title Interest of Early Erectile Rehabilitation With Sildenafil After Radiotherapy and Proctectomy for Rectal Cancer, status recruiting, sponsor University Hospital, Rouen, countries France, us states none listed
- nct NCT07057011, url https://clinicaltrials.gov/study/NCT07057011, phase Not applicable, title Therapeutic Outcomes of Selective Serotonin Reuptake Inhibitors and Phosphodiesterase-5 Inhibitors Combination Therapy Versus Monotherapy, status not-yet-recruiting, sponsor South Valley University, countries Egypt, us states none listed
- nct NCT06839651, url https://clinicaltrials.gov/study/NCT06839651, phase Phase 1, title Umbilical Cord Mesenchymal Stem Cell Secretome in Severe Erectile Dysfunction Non-responsive to Sildenafil, status not-yet-recruiting, sponsor Universitas Indonesia, countries none listed, us states none listed
- nct NCT06872866, url https://clinicaltrials.gov/study/NCT06872866, phase Phase 1, title 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, status recruiting, sponsor Aspargo Labs, Inc, countries United States, us states New York
- nct NCT06510322, url https://clinicaltrials.gov/study/NCT06510322, phase Early phase 1, title Sildenafil to Reduce Vascular Remodeling During Left Ventricular Assist Device Support, status recruiting, sponsor Montefiore Medical Center, countries United States, us states New York
- nct NCT06797479, url https://clinicaltrials.gov/study/NCT06797479, phase Not stated, title Detection of Circulating Therapeutic Monoclonal Antibodies in Biological Samples of Gynecological Cancer Patients., status not-yet-recruiting, sponsor Fondazione Policlinico Universitario Agostino Gemelli IRCCS, countries none listed, us states none listed
- nct NCT06954597, url https://clinicaltrials.gov/study/NCT06954597, phase Phase 2, title Safety and Tolerability of TOP-N53 Applied on Digital Ulcers in Patients With Systemic Sclerosis, status recruiting, sponsor Topadur Pharma AG, countries France, Switzerland, us states none listed
- nct NCT06782659, url https://clinicaltrials.gov/study/NCT06782659, phase Phase 1, title Study to Compare the Effects of Viagra® Vs Hezkue® in Healthy Fasted Male Participants., status not-yet-recruiting, sponsor Aspargo Labs, Inc, countries United States, us states Florida
- nct NCT06753981, url https://clinicaltrials.gov/study/NCT06753981, phase Not stated, title Efficacy and Safety of Triple-targeted Drug Therapy in Treatment-naive Patients With Non-low-risk PAH: A Real-world, Multicenter Study, status recruiting, sponsor Qianfoshan Hospital, countries China, us states none listed
- nct NCT06715280, url https://clinicaltrials.gov/study/NCT06715280, phase Phase 4, title Switching of Sildenafil to Riociguat in CTEPH Patients, status recruiting, sponsor Chinese University of Hong Kong, countries Hong Kong, us states none listed
- nct NCT05782244, url https://clinicaltrials.gov/study/NCT05782244, phase Phase 2, title Sildenafil for Microvasculopathy in Chronic TBI, status recruiting, sponsor University of Pennsylvania, countries United States, us states Pennsylvania
- nct NCT06098833, url https://clinicaltrials.gov/study/NCT06098833, phase Phase 2, title Treatment of Neonatal Encephalopathy With Oral Sildenafil Suspension to Repair Brain Injury Secondary to Birth Asphyxia, status recruiting, sponsor Pia Wintermark, countries United States, Canada, us states Colorado
- nct NCT06324396, url https://clinicaltrials.gov/study/NCT06324396, phase Phase 1, title IMProving DRug Dosing and Outcomes for Single VEntricle Patients With Fontan Associated Liver Disease, status recruiting, sponsor Children's Mercy Hospital Kansas City, countries United States, us states Missouri
- nct NCT06875258, url https://clinicaltrials.gov/study/NCT06875258, phase Phase 4, title PEnile ReHABilitation After Nerve Sparing Robot-assisted Radical Prostatectomy for Prostate Cancer 2.0 (PEHAB-II), status recruiting, sponsor The Netherlands Cancer Institute, countries Netherlands, us states none listed
- nct NCT06317805, url https://clinicaltrials.gov/study/NCT06317805, phase Phase 4, title Initial Triple Therapy Including Parenteral Treprostinil vs Initial Double Oral Therapy in PAH Group I Patients, status recruiting, sponsor AOP Orphan Pharmaceuticals AG, countries Austria, Czechia, France, Germany, Hungary, Italy, Poland, Portugal, Romania, Spain, us states none listed
- nct NCT05201144, url https://clinicaltrials.gov/study/NCT05201144, phase Phase 2, title A Trial of Phosphodiesterase-5 Inhibitor in Neonatal Congenital Diaphragmatic Hernia (TOP-CDH), status recruiting, sponsor University of Utah, countries United States, us states Utah
- nct NCT05061368, url https://clinicaltrials.gov/study/NCT05061368, phase Phase 2, title Oral Sildenafil for Exercise Capacity, Dyspnea and Cardiopulmonary Function in COPD, status recruiting, sponsor University of Alberta, countries Canada, us states none listed
- nct NCT04797286, url https://clinicaltrials.gov/study/NCT04797286, phase Phase 2, title Sildenafil for Early Pulmonary Vascular Disease in Scleroderma, status recruiting, sponsor Johns Hopkins University, countries United States, us states Louisiana, Maryland
- nct NCT04898114, url https://clinicaltrials.gov/study/NCT04898114, phase Phase 1/Phase 2, title Nebulized Magnesium Sulfate and Sildenafil for Persistent Pulmonary Hypertension of Newborn, status recruiting, sponsor Sohag University, countries Egypt, us states none listed
- nct NCT07377084, url https://clinicaltrials.gov/study/NCT07377084, phase Not stated, title Metabolomics of Cancers of the Upper Aerodigestive Tract, status recruiting, sponsor Centre Antoine Lacassagne, countries France, us states none listed
- nct NCT01347216, url https://clinicaltrials.gov/study/NCT01347216, phase Not stated, title COMPERA / COMPERA-KIDS, status recruiting, sponsor Technische Universität Dresden, countries Belgium, Germany, Italy, Switzerland, us states none listed

Source: https://clinicaltrials.gov/api/v2/studies?query.intr=sildenafil&filter.overallStatus=RECRUITING%2CNOT_YET_RECRUITING&pageSize=50&sort=StartDate%3Adesc&countTotal=true&fields=NCTId%2CBriefTitle%2COverallStatus%2CPhase%2CLeadSponsorName%2CStartDate%2CLocationCountry%2CLocationState

## Sources

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

### 1. Viagra (sildenafil citrate) tablets label, revised August 2017

Type: label

Tier: primary

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf

### 2. Revatio (sildenafil) tablets, oral suspension and injection label, revised December 2024

Type: label

Tier: primary

Source: https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/021845Orig1s028,022473Orig1s019lbl.pdf

### 3. Drugs@FDA: Viagra (sildenafil citrate) tablets, application 020895

Type: regulatory

Tier: primary

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895

### 4. Drugs@FDA: Revatio (sildenafil citrate) tablets, application 021845

Type: regulatory

Tier: primary

Source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021845

### 5. FDA: bulk drug substances used in compounding under section 503A

Type: regulatory

Tier: primary

Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act

### 6. FDA: 503A bulk drug substances category list, updated May 2026

Type: regulatory

Tier: primary

Source: https://www.fda.gov/media/94155/download

### 7. FDA health fraud notice: sexual enhancement supplement with hidden sildenafil and tadalafil, 29 May 2026

Type: regulatory

Tier: primary

Source: https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients

### 8. FDA health fraud notice: sexual enhancement products with hidden sildenafil, 2020 to 2026

Type: regulatory

Tier: primary

Source: https://www.fda.gov/drugs/medication-health-fraud-notifications/magnum-brand-products-may-be-harmful-due-hidden-drug-ingredients

### 9. FDA warning letter on a product sold as a supplement with undeclared sildenafil, 28 August 2018

Type: regulatory

Tier: primary

Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/duy-drugs-inc-542933-08282018

### 10. FDA warning letter on claims that compounded sildenafil is a generic Viagra, 9 September 2025

Type: regulatory

Tier: primary

Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025

### 11. Randomized trial: oral sildenafil for erectile dysfunction, 1998

Type: rct

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/9580646/

### 12. Randomized trial: sildenafil for pulmonary arterial hypertension in adults, 2005

Type: rct

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/16291984/

### 13. Randomized dose-ranging trial: oral sildenafil in children with pulmonary arterial hypertension, 2012

Type: rct

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/22128226/

### 14. Systematic review: PDE5 inhibitors and hormone treatments for erectile dysfunction, 2009

Type: systematic-review

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/19884626/

### 15. Case-crossover study: sudden optic nerve damage (NAION) and PDE5 inhibitor use, 2015

Type: human-trial

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/25358826/

### 16. Study: unapproved drug ingredients in dietary supplements named in FDA warnings, 2007 to 2016

Type: reference

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/30646238/

### 17. Rat study: dapagliflozin and sildenafil in pulmonary arterial hypertension, 2022

Type: animal

Tier: peer-reviewed

Source: https://pubmed.ncbi.nlm.nih.gov/35413880/

### 18. National Law Review: FDA's focus returns to compounding and telehealth

Type: legal-analysis

Tier: legal-analysis

Source: https://natlawreview.com/article/fdas-focus-returns-compounding-and-telehealth-another-wave-warning-letters

### 19. CBS News: many dietary supplements contain unapproved, dangerous ingredients, October 2018

Type: reference

Tier: established-news

Source: https://www.cbsnews.com/news/many-dietary-supplements-contain-unapproved-dangerous-ingredients-study-finds/

### 20. ClinicalTrials.gov NCT04797286: sildenafil for early pulmonary vascular disease in scleroderma

Type: reference

Tier: primary

Source: https://clinicaltrials.gov/study/NCT04797286

### 21. ClinicalTrials.gov NCT05201144: sildenafil in newborns with congenital diaphragmatic hernia

Type: reference

Tier: primary

Source: https://clinicaltrials.gov/study/NCT05201144

Last verified: 2026-10-26.

Sources:

- https://clinicaltrials.gov/api/v2/studies?query.intr=sildenafil&filter.overallStatus=RECRUITING%2CNOT_YET_RECRUITING&pageSize=50&sort=StartDate%3Adesc&countTotal=true&fields=NCTId%2CBriefTitle%2COverallStatus%2CPhase%2CLeadSponsorName%2CStartDate%2CLocationCountry%2CLocationState
- https://peptideindex.ai/methodology#evidence-grade
- https://peptideindex.ai/methodology#short-answer
- https://pubmed.ncbi.nlm.nih.gov/16291984/
- https://pubmed.ncbi.nlm.nih.gov/19884626/
- https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf
- https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895
- https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients

[^1]: Viagra (sildenafil citrate) tablets label, revised August 2017 https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s049lbl.pdf
[^2]: Revatio (sildenafil) tablets, oral suspension and injection label, revised December 2024 https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/021845Orig1s028,022473Orig1s019lbl.pdf
[^3]: Drugs@FDA: Viagra (sildenafil citrate) tablets, application 020895 https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020895
[^4]: Drugs@FDA: Revatio (sildenafil citrate) tablets, application 021845 https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021845
[^5]: FDA: bulk drug substances used in compounding under section 503A https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act
[^6]: FDA: 503A bulk drug substances category list, updated May 2026 https://www.fda.gov/media/94155/download
[^7]: FDA health fraud notice: sexual enhancement supplement with hidden sildenafil and tadalafil, 29 May 2026 https://www.fda.gov/drugs/medication-health-fraud-notifications/x10-natural-enhancement-supplement-may-be-harmful-due-hidden-drug-ingredients
[^8]: FDA health fraud notice: sexual enhancement products with hidden sildenafil, 2020 to 2026 https://www.fda.gov/drugs/medication-health-fraud-notifications/magnum-brand-products-may-be-harmful-due-hidden-drug-ingredients
[^9]: FDA warning letter on a product sold as a supplement with undeclared sildenafil, 28 August 2018 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/duy-drugs-inc-542933-08282018
[^10]: FDA warning letter on claims that compounded sildenafil is a generic Viagra, 9 September 2025 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/getfitmedical-llc-dba-getfitmedical-715801-09092025
[^11]: Randomized trial: oral sildenafil for erectile dysfunction, 1998 https://pubmed.ncbi.nlm.nih.gov/9580646/
[^12]: Randomized trial: sildenafil for pulmonary arterial hypertension in adults, 2005 https://pubmed.ncbi.nlm.nih.gov/16291984/
[^13]: Randomized dose-ranging trial: oral sildenafil in children with pulmonary arterial hypertension, 2012 https://pubmed.ncbi.nlm.nih.gov/22128226/
[^14]: Systematic review: PDE5 inhibitors and hormone treatments for erectile dysfunction, 2009 https://pubmed.ncbi.nlm.nih.gov/19884626/
[^15]: Case-crossover study: sudden optic nerve damage (NAION) and PDE5 inhibitor use, 2015 https://pubmed.ncbi.nlm.nih.gov/25358826/
[^16]: Study: unapproved drug ingredients in dietary supplements named in FDA warnings, 2007 to 2016 https://pubmed.ncbi.nlm.nih.gov/30646238/
[^17]: Rat study: dapagliflozin and sildenafil in pulmonary arterial hypertension, 2022 https://pubmed.ncbi.nlm.nih.gov/35413880/
[^18]: National Law Review: FDA's focus returns to compounding and telehealth https://natlawreview.com/article/fdas-focus-returns-compounding-and-telehealth-another-wave-warning-letters
[^19]: CBS News: many dietary supplements contain unapproved, dangerous ingredients, October 2018 https://www.cbsnews.com/news/many-dietary-supplements-contain-unapproved-dangerous-ingredients-study-finds/
[^20]: ClinicalTrials.gov NCT04797286: sildenafil for early pulmonary vascular disease in scleroderma https://clinicaltrials.gov/study/NCT04797286
[^21]: ClinicalTrials.gov NCT05201144: sildenafil in newborns with congenital diaphragmatic hernia https://clinicaltrials.gov/study/NCT05201144