Sildenafil
VIAGRA
Pronunciation: sil-DEN-a-fil (vye-AG-ra)
“Slide to fill (Niagara)”
What it isPDE5 inhibitor; erectile dysfunction and pulmonary arterial hypertension.
Why this onePDE6 spillover produces its characteristic blue-tinted vision, distinguishing it from other PDE5 inhibitors.
What limits itNitrates can cause fatal hypotension and are absolutely contraindicated; CYP3A4 inhibitors raise exposure.
FDA-approved for
- erectile dysfunction (1998)
- pulmonary arterial hypertension (2005)
Off-label
- Raynaud phenomenon
- high-altitude pulmonary edema
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Erectile dysfunction | Adult males | 50 mg PRN ~1 h before sexual activity | 25-100 mg PRN | 100 mg; once daily max frequency |
Renal Mild-moderate (CLcr 30-80): no adjustment; severe (<30 mL/min): consider start 25 mg
Hepatic Consider start 25 mg (Child-Pugh A/B); Child-Pugh C not studied
Maximum dosing frequency once per day
Instructions
- Take ~1 h (range 30 min-4 h) before sexual activity
- May take with or without food
- With ritonavir: max 25 mg per 48 h
- With strong CYP3A4 inhibitors: consider start 25 mg
- Age >65 yr: consider start 25 mg
Available strengths
- tab 25, 50, 100 mg
- tab 20 mg (Revatio (PAH) generic)
Contraindications
- Nitric oxide donors / nitrates (organic nitrates or nitrites) in any form
- Guanylate cyclase stimulators (e.g., riociguat)
Cautions
- Cardiac risk of sexual activity in preexisting cardiovascular disease
- Prolonged erection / priapism
- NAION (sudden vision loss)
- Sudden hearing loss
- Hypotension with alpha-blockers or antihypertensives
- Increased exposure with ritonavir
- Effects on bleeding
Adverse reactions
- Headache
- Flushing
- Dyspepsia
- Abnormal/color vision
- Nasal congestion
- Back pain
- Myalgia
- Nausea
- Dizziness
- Rash
Pregnancy Not indicated in females; no human data; animal studies show no adverse developmental outcomes
Lactation Not indicated in females; sildenafil and metabolite present in human milk (limited data)
Cost
Generic entry2012
NO BOXED WARNINGS
Principal riskFatal hypotension with nitrates
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
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