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PDE5 Inhibitor — Pulmonary Arterial Hypertension Pregnancy: Use with caution — PAH in pregnancy is high risk; sildenafil used in specialist centres; consult pulmonary hypertension team

Sildenafil

Brand names: Revatio (PAH), Viagra (erectile dysfunction — different indication)

Adult dose

Dose: 20 mg three times daily
Route: Oral
Frequency: Three times daily (approximately 4–6 hours apart)
Max: 20 mg three times daily (Revatio licence); higher doses used off-label in specialist centres
PDE5 inhibitor for pulmonary arterial hypertension (PAH — WHO Group 1) — inhibits PDE5 in pulmonary vascular smooth muscle, increasing cGMP, causing vasodilation. Used as monotherapy or combination therapy with endothelin receptor antagonists (bosentan, ambrisentan, macitentan) or prostanoids.

Paediatric dose

Dose: Seek specialist opinion mg/kg
Route: Oral
Frequency: Three times daily
Max: 20 mg three times daily (EMA licensed); higher weight-based doses used in paediatric PAH
BNFc: licensed from birth for PAH — weight-based dosing; specialist paediatric cardiology/respiratory input required. Note: EMA found reduced survival at higher doses in children — use lowest effective dose

Dose adjustments

Renal

No dose adjustment required for Revatio 20 mg TDS

Hepatic

Use with caution in severe hepatic impairment — increased exposure

Paediatric weight-based calculator

BNFc: licensed from birth for PAH — weight-based dosing; specialist paediatric cardiology/respiratory input required. Note: EMA found reduced survival at higher doses in children — use lowest effective dose

Clinical pearls

  • SUPER-1 trial: sildenafil 20 mg TDS significantly improved 6-minute walk distance and pulmonary vascular resistance in WHO functional class II–III PAH
  • Nitrate absolute contraindication: concurrent nitrate use is the most important drug interaction — mechanism is additive cGMP accumulation causing catastrophic hypotension; always take full medication history
  • Riociguat absolute contraindication: both drugs increase cGMP via different mechanisms — combination causes severe hypotension; never co-prescribe
  • EMA paediatric warning: higher weight-adjusted doses not associated with improved survival in children — use 10 mg TDS as starting dose in children
  • Combination PAH therapy: sildenafil commonly combined with endothelin receptor antagonists (ambrisentan, macitentan) — AMBITION trial showed superior outcomes with combination vs monotherapy
  • 'Sildenafil holiday' concept obsolete — withdrawal causes rebound PAH worsening; do not abruptly stop

Contraindications

  • Concomitant nitrates (absolute — severe hypotension)
  • Concomitant guanylate cyclase stimulators (riociguat — absolute contraindication)
  • Severe hypotension (BP <90/50 mmHg)
  • Recent stroke or MI (<6 months)

Side effects

  • Headache (most common)
  • Flushing
  • Dyspepsia
  • Epistaxis
  • Visual disturbances (blue tinge, blurred vision)
  • Hypotension
  • Priapism (rare)

Interactions

  • Nitrates — ABSOLUTE CONTRAINDICATION (severe, potentially fatal hypotension)
  • Riociguat — ABSOLUTE CONTRAINDICATION
  • CYP3A4 inhibitors (azoles, macrolides, ritonavir) — increase sildenafil levels; dose reduction needed
  • Alpha-blockers — additive hypotension

Monitoring

  • 6-minute walk distance (6MWD) — primary efficacy measure
  • NT-proBNP (or BNP)
  • Right heart catheterisation (diagnostic and follow-up)
  • Echocardiography
  • Blood pressure

Reference: BNFc; BNF 90; BNFc; SUPER-1 Trial (Galiè et al. NEJM 2005); AMBITION Trial (Galiè et al. NEJM 2015); ESC/ERS PAH Guidelines 2022; SPC Revatio. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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