Sildenafil
Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor originally developed for angina and subsequently approved for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). As Viagra, it is the most recognized ED medication worldwide. As Revatio, it is used at lower doses for PAH to improve exercise capacity. Its on-demand dosing makes it the standard first-line oral therapy for ED.
Exploratory record, not a reviewed medical publication.
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This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.
What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor originally developed for angina and subsequently approved for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). NutriStack rates the supporting evidence as strong. Common adult dosing is 50 mg as needed approximately 30-60 minutes before sexual activity (may adjust to 25-100 mg); for PAH: 20 mg three times daily (as prescribed by your physician), though a prescriber sets the actual dose. This profile indexes 10 sources.
- Headache
- Flushing
- Dyspepsia
- Concurrent use with nitrates (nitroglycerin, isosorbide), risk of severe, potentially fatal hypotension
- Concurrent use with riociguat (Adempas)
The bottom line
Evidence rating strong. Most-documented uses: effective first-line oral treatment for erectile dysfunction, improves exercise capacity in pulmonary arterial hypertension, rapid onset allows on-demand use. 10 sources indexed (2023–2025), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Selectively inhibits phosphodiesterase type 5 (PDE5), the enzyme that degrades cyclic GMP (cGMP) in penile corpus cavernosum smooth muscle. During sexual stimulation, nitric oxide is released, activating guanylate cyclase to produce cGMP, which relaxes smooth muscle and increases blood flow. By preventing cGMP breakdown, sildenafil potentiates the erectile response. In PAH, the same mechanism relaxes pulmonary vascular smooth muscle, reducing pulmonary artery pressure.
Dosing & protocol.
High-fat meals delay absorption by approximately 1 hour and reduce peak concentration by 29%; for fastest onset, take on an empty stomach. Bioavailability ~41%.
Full safety detail.
Side effects
- Headache
- Flushing
- Dyspepsia
- Nasal congestion
- Visual disturbances (blue-tinged vision, increased light sensitivity, due to mild PDE6 inhibition in retina)
- Dizziness
- Priapism (rare)
Contraindications
- Concurrent use with nitrates (nitroglycerin, isosorbide), risk of severe, potentially fatal hypotension
- Concurrent use with riociguat (Adempas)
- Known hypersensitivity to sildenafil1,2
- Recent stroke or myocardial infarction (within 6 months)
- Severe hepatic impairment
- Conditions where sexual activity is inadvisable (unstable angina, severe heart failure)
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
4- 1Sildenafil and risk of Alzheimer disease: a systematic review and meta-analysisPMIDChua WY, Lim LKE, Wang JJD et al. · Aging · 2025
Chua WY, Lim LKE, Wang JJD et al.. Sildenafil and risk of Alzheimer disease: a systematic review and meta-analysis. Aging. 2025
- 2Physiological Effects of Sildenafil Versus Placebo at High Altitude: A Systematic ReviewPMIDPoudel S, Gautam S, Adhikari P et al. · High altitude medicine & biology · 2024
Poudel S, Gautam S, Adhikari P et al.. Physiological Effects of Sildenafil Versus Placebo at High Altitude: A Systematic Review. High altitude medicine & biology. 2024
- 3Prophylactic sildenafil to prevent bronchopulmonary dysplasia: A systematic review and meta-analysisPMIDHirata K, Nakahari A, Takeoka M et al. · Pediatrics international : official journal of the Japan Pediatric Society · 2024
Hirata K, Nakahari A, Takeoka M et al.. Prophylactic sildenafil to prevent bronchopulmonary dysplasia: A systematic review and meta-analysis. Pediatrics international : official journal of the Japan Pediatric Society. 2024
- 4Sildenafil for congenital heart diseases induced pulmonary hypertension, a meta-analysis of randomized controlled trialsPMIDAwad AK, Gad ER, Abdelgalil MS et al. · BMC pediatrics · 2023
Awad AK, Gad ER, Abdelgalil MS et al.. Sildenafil for congenital heart diseases induced pulmonary hypertension, a meta-analysis of randomized controlled trials. BMC pediatrics. 2023
Reviews & position papers
1- 5Function of sildenafil on diseases other than urogenital system: An umbrella reviewPMIDChen Z, Huang Y, Cao D et al. · Frontiers in pharmacology · 2023
Chen Z, Huang Y, Cao D et al.. Function of sildenafil on diseases other than urogenital system: An umbrella review. Frontiers in pharmacology. 2023
Reference material
5- 6Goldstein I et al. Oral sildenafil in the treatment of erectile dysfunction. N Engl J Med. 1998;338(20):1397-1404.Source linkedPMID
- 7Galiè N et al. Sildenafil citrate therapy for pulmonary arterial hypertension. N Engl J Med. 2005;353(20):2148-2157.Source linkedPMID
- 8Carson CC et al. The efficacy and safety of sildenafil citrate (Viagra) in clinical populations. Urology. 2002;60(2 Suppl 2):12-20.Source linkedPMID
- 9Gong B, Ma M, Xie W et al.. Direct comparison of tadalafil with sildenafil for the treatment of erectile dysfunction: a systematic review and meta-analysis. International urology and nephrology. 2017Source linkedPMID
- 10Krishnappa P, Fernandez-Pascual E, Carballido J et al.. Sildenafil/Viagra in the treatment of premature ejaculation. International journal of impotence research. 2019Source linkedPMID
Common questions.
Quick answers about Sildenafil, drawn from the data on this page.
What is Sildenafil?
Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor originally developed for angina and subsequently approved for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). As Viagra, it is the most recognized ED medication worldwide. As Revatio, it is used at lower doses for PAH to improve exercise capacity. Its on-demand dosing makes it the standard first-line oral therapy for ED.
What is Sildenafil used for?
Commonly cited benefits of Sildenafil include: Effective first-line oral treatment for erectile dysfunction; Improves exercise capacity in pulmonary arterial hypertension; Rapid onset allows on-demand use; Well-studied safety profile over 25+ years. NutriStack rates the overall evidence as strong.
What is a typical dose of Sildenafil?
A typical adult dose of Sildenafil is 50 mg as needed approximately 30-60 minutes before sexual activity (may adjust to 25-100 mg); for PAH: 20 mg three times daily (as prescribed by your physician). The commonly recommended form is Oral tablet; also available as oral suspension (Revatio) and IV injection for PAH. These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of Sildenafil?
Reported side effects include headache, flushing, dyspepsia, nasal congestion, visual disturbances (blue-tinged vision, increased light sensitivity, due to mild pde6 inhibition in retina), dizziness. This is educational information; check with a healthcare professional before use.
How strong is the evidence for Sildenafil?
NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Use this with your stack
Sildenafil in NutriStack.
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