Sildenafil
Revatio (PAH) / Viagra (erectile dysfunction)
pulmonary vasodilatororal · IVOnset: 30–60 minutes (oral)Duration: 4–6 hours
Mechanism of Action
Phosphodiesterase-5 (PDE-5) inhibitor. PDE-5 degrades cGMP in smooth muscle. By inhibiting PDE-5 → increased cGMP → smooth muscle relaxation and vasodilation. Potentiates effect of nitric oxide in pulmonary vasculature.
Dosing
Adult
PAH: 20 mg TID (Revatio). May increase to 80 mg TID
Pediatric
PPHN: 0.5–2 mg/kg/dose q6–8h oral (off-label)
IV form available for patients unable to take orally
Indications
- Pulmonary arterial hypertension (WHO Group I) — FDA approved
- PPHN (off-label, oral)
- Adjunct to weaning inhaled nitric oxide
Contraindications
- Concurrent nitrates (severe hypotension — absolute contraindication)
- Concurrent riociguat (PDE-5 inhibitor interaction)
- Recent stroke or MI (<6 months)
- Severe hepatic impairment
Side Effects
- Systemic hypotension
- Headache
- Flushing
- Epistaxis
- Visual disturbances (blue-green color vision)
- Priapism (rare)
- Worsening oxygenation in ARDS (may worsen V/Q matching — not selective)
Monitoring Parameters
- Blood pressure
- SpO2
- Pulmonary artery pressures
- Exercise tolerance (6-minute walk test)
- Visual symptoms
Drug Interactions
- Nitrates (absolute contraindication — severe hypotension)
- Alpha-blockers (hypotension)
- CYP3A4 inhibitors (increase sildenafil levels)
- iNO (potentiated vasodilation — additive)
- Riociguat (contraindicated — same pathway)
Clinical Pearls
- Oral agent — improves PAH without IV access required
- In ARDS, may worsen V/Q matching because it's not selective to ventilated lung (unlike iNO)
- Used to facilitate weaning from inhaled NO
- Avoid in ARDS as routine therapy — does not improve outcomes
- Contraindication with nitrates is a critical NBRC exam point
Mnemonic
💡 Sildenafil: Stays in the lung via PDE5 (but not selective like iNO)
NBRC High-Yield
- PDE-5 inhibitor — oral pulmonary vasodilator
- Absolute contraindication: nitrates (severe hypotension)
- Not selective to pulmonary vasculature — may worsen V/Q in ARDS
- Used to wean inhaled nitric oxide in PAH
- 20 mg TID for PAH (Revatio formulation)