pulmonary vasodilator

Sildenafil

Revatio (PAH) / Viagra (erectile dysfunction)

Route: oral · IV
Onset: 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)

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