Sexual health
Viagra
sildenafil / pronounced [sil den' a fil]
First PDE5 inhibitor for ED. 30-60 min onset, 4-6 hour duration. Now widely available as generic sildenafil.
- Manufacturer
- Pfizer
- FDA approved
- 1998
FDA-approved for
- Erectile dysfunction
Why is Viagra prescribed?
Viagra is the original brand-name sildenafil, FDA-approved for ED in 1998. The patent expired in 2017, making generic sildenafil widely available at a fraction of the brand price.
FDA-approved indications:
- Erectile dysfunction
How does Viagra work?
Sildenafil blocks the PDE5 enzyme, which breaks down cGMP in penile tissue. With cGMP preserved, blood vessels stay relaxed and erection is maintained when sexually stimulated. Does not cause erection without arousal.
Who qualifies for Viagra?
Adult men with ED. Contraindicated with nitrate medications (severe hypotension risk). Caution with alpha-blockers, certain antifungals, and cardiovascular disease.
How should Viagra be used?
25-100mg as needed, 30-60 minutes before sexual activity. Maximum 1 dose per 24 hours.
Pharmacokinetic timing: onset 30 min · peak 60 min · duration ~240 min
What should I do if I forget a dose?
Viagra is taken as-needed before sexual activity, not on a daily schedule. There's no 'missed dose' in the traditional sense. Take 30-60 minutes before intended activity. Do not exceed one dose per 24 hours. If a planned activity doesn't happen, don't take an extra dose later same day — wait for next session.
What side effects can Viagra cause?
Headache (10-15%), flushing, nasal congestion, mild visual changes (slight blue tint). Stop and seek care for chest pain, sudden vision loss, or hearing loss.
What interactions should clinicians watch for?
Most clinically critical: nitrates (nitroglycerin, isosorbide) — combination can cause severe, life-threatening blood pressure drop. Never use Viagra within 24 hours of a nitrate. Caution with alpha-blockers (doxazosin, terazosin — hypotension risk; separate doses by at least 4 hours). Caution with CYP3A4 inhibitors (ketoconazole, ritonavir, erythromycin — increase Viagra blood levels; dose reduction needed). Generally safe with most other medications; disclose all to prescriber.
What special precautions should I follow?
Pregnancy & lactation
Viagra is FDA-approved for men only. Sildenafil under the brand name Revatio is occasionally prescribed for pulmonary arterial hypertension in pregnancy at specialist discretion, but recreational/ED use does not apply to pregnant patients. Not a relevant pregnancy concern for the typical Viagra user.
Alcohol
Moderate alcohol intake is generally compatible with Viagra. Heavy drinking can cause vasodilation that may amplify side effects (headache, flushing, dizziness) or paradoxically inhibit erection through alcohol's direct effect on sexual function. Avoid combining Viagra with binge drinking. One to two drinks is typically fine.
What does Viagra cost?
Branded Viagra ~$70/tablet. Generic sildenafil $1-5/tablet at most pharmacies with GoodRx-style coupons. Telehealth platforms charge $30-90/month for a typical monthly supply.
Primary sources
Related clinical resources
What clinicians say
Quotes from published interviews, peer-reviewed commentary, and conference presentations. Each is attributed and linked to the original source.
“Oral sildenafil is an effective, well-tolerated treatment for men with erectile dysfunction. Significant improvements were observed in all parameters of sexual function compared with placebo.”
Source: New England Journal of Medicine — Sildenafil Study Group landmark trial (Oral Sildenafil in the Treatment of Erectile Dysfunction) (May 1998 — DOI 10.1056/NEJM199805143382001)
“The concomitant use of Viagra with nitrates in any form is contraindicated. Following nitric oxide stimulation, sildenafil potentiates the hypotensive effect of nitrates, which may result in severe hypotension.”
Source: FDA-approved Viagra (sildenafil) prescribing information — current label (Approved March 1998; current label 2017)