Sildenafil
sil-DEN-ah-fil
The original erectile dysfunction medication — relaxes blood vessels to improve blood flow when aroused.
Also known as: Viagra
FDA approved for: Erectile dysfunction · Pulmonary arterial hypertension (Revatio)
Last reviewed: April 2026
What It Does
Sildenafil blocks an enzyme (PDE5) that breaks down a chemical responsible for relaxing blood vessels. When you're sexually aroused, this allows more blood to flow where it's needed. It doesn't create arousal — it makes the physical response work better when arousal is present.
Why People Take It
How It's Administered
Oral
Tablet taken 30–60 minutes before sexual activity
Frequency
As needed (max once daily)
Pain Level
○○○ None
Self-Administered
Yes — at home
Typical Range
25mg – 100mg
What To Expect
30–60 minutes
Effects begin. Works faster on an empty stomach.
1–3 hours
Peak effectiveness window.
4–6 hours
Effects gradually wear off.
Side Effects
Overall: Mild to Moderate
Very Common (>10%)
Headache
Due to blood vessel dilation. Usually mild.
Common (1–10%)
Flushing
Warm feeling and redness in face and chest.
Nasal congestion
Stuffy nose from vasodilation.
Uncommon (0.1–1%)
Vision changes
Blue tint to vision or light sensitivity.
Rare (<0.1%)
Priapism
Erection lasting 4+ hours — seek emergency care immediately.
Call your doctor if you experience this.
Who Should NOT Take This
• Currently taking nitrates (nitroglycerin)
• Severe heart disease or recent heart attack
• Very low blood pressure
• Recent stroke
Drug Interactions
• Nitrates (nitroglycerin) — LIFE-THREATENING blood pressure drop, NEVER combine
• Alpha-blockers — increased hypotension risk
• CYP3A4 inhibitors — may increase sildenafil levels
Pregnancy: Not indicated for use in women. If prescribed off-label, do not use during pregnancy.
Clinical Details
Compare With Similar Peptides
Sildenafil is shorter-acting (4–6 hours) vs tadalafil (up to 36 hours). Sildenafil is better for on-demand use; tadalafil for regular daily dosing.
Tadalafil
A long-acting ED medication that can last up to 36 hours — also used daily at low doses for ongoing support.
PT-141 (Bremelanotide)
A peptide that increases sexual desire by acting on the brain — works differently from ED medications that only improve blood flow.
Frequently Asked Questions
This peptide is available through our protocols.
FDA-approved for at least one indication. Your provider will determine if this is appropriate for you.