02
What Is It?
Sildenafil is a prescription oral medication for erectile dysfunction. It was the first PDE5 inhibitor approved by the FDA and remains a reference point for every product in this class.
Product Profile & Review
FDA APPROVEDPRESCRIPTION
Sildenafil
The foundational PDE5 inhibitor, approved in 1998, with one of the deepest clinical evidence bases in men's health.
Also known as: Sildenafil citrate, Viagra (brand), Revatio (PAH brand)
- Written by
- SynMale Editorial
- Originally Published
- October 2026
- Last Updated
- October 2026
- Medical Review
- Not yet independently reviewed
Executive Summary
- What is it?
- Prescription PDE5 Inhibitor (Prescription Medication).
- What does it contain or claim to contain?
- Sildenafil citrate (verified)
- How well verified is this specific product?
- Well Established
- Most important thing to know
- Well-established prescription PDE5 inhibitor with predictable on-demand use.
A
Ingredient
Sildenafil citrate
Product Type
Prescription PDE5 Inhibitor
Regulatory Status
FDA Approved
Verification
Well Established
03
Claimed Active Ingredients
- VERIFIED INGREDIENTSildenafil citrate25 / 50 / 100 mg (FDA-approved product)
A claimed ingredient is what a label or seller states. It is not treated as confirmed.
04
What Can We Verify?
Established
- Mechanism, pharmacokinetics and efficacy are documented in decades of controlled trials.
- Dosage is verified in FDA-approved and properly regulated generic products.
- Manufacturing is subject to FDA quality oversight when dispensed through licensed pharmacies.
Uncertain or unverified
- Products sold outside licensed channels cannot be assumed to contain the stated dose or ingredient.
05
How It Works
Sexual stimulation releases nitric oxide (NO) in penile tissue. NO raises levels of cyclic GMP (cGMP), which relaxes the smooth muscle of the corpus cavernosum so arteries widen and blood flows in.
The enzyme PDE5 normally breaks cGMP down. PDE5 inhibitors block that enzyme, so cGMP persists and smooth-muscle relaxation is sustained. They do not create arousal—stimulation is still required.
06
Evidence Level
AStrong Clinical Evidence
Grades run from A (strong clinical evidence) to F (unsupported or contradicted). How we grade.
07
Clinical Profile
- Drug Class
- PDE5 Inhibitor
- Typical Onset
- 30–60 minutes
- Effective Window
- About 4–6 hours
- Half-Life
- About 3–5 hours
- Typical Medical Dosing
- 25 / 50 / 100 mg, as prescribed
- Food Interaction
- High-fat meals can delay onset by about an hour
- Alcohol Considerations
- Heavy drinking can worsen ED and add to blood-pressure lowering
- Daily vs On-Demand
- On-demand
08
Benefits / Potential Advantages
- Extensive track record since 1998
- Predictable onset and a defined duration
- Several dose strengths allow individual adjustment by a clinician
- Short half-life means effects clear relatively quickly
09
Limitations
- Shorter window than tadalafil
- Absorption slowed by high-fat meals
- Requires planning around timing
10
Side Effects & Precautions
Common effects
Headache, facial flushing, nasal congestion, indigestion, and temporary blue-tinted or light-sensitive vision.
Major interactions & warnings
- • Nitrates (e.g. nitroglycerin, isosorbide): combined use can cause a severe, potentially life-threatening drop in blood pressure. Contraindicated.
- • Riociguat and other guanylate cyclase stimulators: contraindicated for the same reason.
- • Alpha-blockers (e.g. doxazosin, tamsulosin): not universally contraindicated, but combined use can lower blood pressure and requires medical guidance on dosing and timing.
- • Significant cardiovascular disease: sexual activity itself carries cardiac load; a clinician should assess fitness before treatment.
- • Priapism: an erection lasting more than 4 hours is a medical emergency.
- • Sudden vision loss (rare NAION reports) or sudden hearing loss: stop use and seek urgent care.
11
Regulatory Status
FDA ApprovedFDA Cleared DeviceNot FDA ApprovedDietary SupplementCompounded MedicationForeign-Market MedicationUnknownUnverified
FDA-approved for erectile dysfunction. Generic sildenafil from licensed manufacturers is held to the same standards as the brand.
12
Marketing Claims vs. Evidence
Claim
What the Evidence Shows
“Works instantly”
Onset is typically 30–60 minutes and requires sexual stimulation.
“Causes arousal”
Sildenafil does not create desire; it supports the physiological response to stimulation.
13
Counterfeit / Adulteration Risk
Documented
- Sildenafil is the drug most often found hidden in counterfeit pills and “natural” supplements.
Unconfirmed / speculative
None noted.
Review Scorecard
Onset Speed
4.0/5
Duration
3.5/5
Potency & Reliability
4.5/5
Tolerability
4.0/5
Convenience
3.5/5
Overall Score
4.0/5
SynMale scores are editorial comparison tools and are not medical efficacy guarantees.
ⓘ About SynMale Ratings
SynMale numerical ratings are editorial comparison tools informed by:
- Consistency of published clinical efficacy results
- Predictability of onset and duration
- Established dosing information
- Adverse-effect data
- Treatment discontinuation data where available
- Practical dosing flexibility
- Strength and consistency of available clinical evidence
These numbers are not efficacy percentages, clinical success rates, or predictions of individual response.
Full methodology → SynMale Verdict
WELL ESTABLISHED
One of the best-characterised medications in men's health, with reliable efficacy and a well-understood safety profile when prescribed appropriately.
Bottom Line
What You Should Know
Sildenafil is a proven, FDA-approved treatment with predictable timing. It requires sexual stimulation and works best on an empty stomach. It must never be combined with nitrates or riociguat. Products sold outside licensed pharmacies may not contain what they claim.