PDE5 Inhibitor (Paediatric Pulmonary Hypertension) Pregnancy: Paediatric use. In pregnancy, sildenafil has been studied for IUGR (STRIDER trial) — showed no benefit and possible harm; NOT recommended in pregnancy for obstetric indications.

Sildenafil (Paediatric — PPHN / PAH)

Brand names: Revatio (paediatric), Viagra (urology — adult)

Adult dose

Dose: PAH adults: 20 mg three times daily (Revatio indication)

Route: Oral

Frequency: Three times daily

Max: 20 mg three times daily for PAH (higher doses no added benefit — MHRA warning for chronic PAH)

Adult dose for pulmonary arterial hypertension — 20 mg three times daily. NOT 100 mg as for erectile dysfunction. Paediatric doses differ — see below. Source: BNF 90.

Paediatric dose

Dose: PPHN (neonates, off-label): 0.5–1 mg/kg every 6 hours orally. PAH (chronic, children ≥1 year): <20 kg: 10 mg three times daily; ≥20 kg: 20 mg three times daily mg/kg

Route: Oral or nasogastric (PPHN — liquid preparation). Oral tablet/suspension (PAH)

Frequency: Every 6 hours (PPHN); three times daily (PAH)

Max: 20 mg per dose (three times daily for chronic PAH)

PPHN (persistent pulmonary hypertension of newborn): off-label, specialist neonatal use — IV iloprost or inhaled NO preferred. Chronic paediatric PAH: licensed from 1 year. MHRA WARNING for chronic PAH: long-term use (>72 weeks) at high doses (20 mg three times daily) in children 1–17 years showed INCREASED MORTALITY vs low doses (1 mg/kg three times daily) in STARTS-2 trial. Use lowest effective dose. Source: BNF for Children 2024; NICE TA564; MHRA 2014 warning. (PPHN) or fixed dose (PAH)

Dose adjustments

Renal

Severe renal impairment (eGFR <30 mL/min): reduce starting dose to 10 mg three times daily and titrate cautiously.

Hepatic

Mild-moderate hepatic impairment: reduce starting dose to 10 mg three times daily. Severe: not recommended.

Paediatric weight-based calculator

Patient weight (kg)

Clinical pearls

PPHN mechanism: at birth, pulmonary vascular resistance falls normally as lungs expand. In PPHN, resistance remains high → right-to-left shunting through patent ductus/foramen ovale → severe hypoxaemia. Sildenafil inhibits PDE5 in pulmonary vasculature → increased cGMP → pulmonary arterial dilation → reduced pulmonary resistance. Inhaled nitric oxide (iNO) is first-line; sildenafil is used as adjunct or when iNO unavailable.
MHRA 2014 STARTS-2 warning — critical: the STARTS-2 long-term extension trial in paediatric PAH showed significantly higher mortality in high-dose sildenafil (20 mg three times daily) vs low-dose (1 mg/kg three times daily). MHRA issued warning: do not use high doses long-term in paediatric PAH (1–17 years). Use lowest dose that controls symptoms and reassess regularly.
Nitrate interaction — most important safety rule: sildenafil causes profound irreversible hypotension when combined with any nitrate (including GTN patches, sprays, tablets; amyl nitrite; isosorbide). Combined use can be fatal. In paediatric cardiac patients who may be on multiple cardiac medications, always screen the full medication list before prescribing.
Vision monitoring: PDE6 inhibition in rod photoreceptors causes colour vision disturbance (blue-green tinge, increased light sensitivity). Non-arteritic anterior ischaemic optic neuropathy (NAION) is rare but stop drug immediately if sudden painless vision loss — irreversible if not managed promptly.
Licensed vs off-label: Revatio (20 mg tablets, 10 mg/mL oral suspension) is licensed for PAH in adults and children ≥1 year. PPHN use in neonates is off-label — specialist neonatal cardiologist or intensivist should prescribe. iNO (inhaled nitric oxide) remains first-line for PPHN. Source: BNF for Children 2024; NICE TA564; MHRA Drug Safety Update 2014 (paediatric mortality).

Contraindications

Concurrent nitrates (absolute — profound hypotension, potentially fatal)
Concurrent riociguat or other sGC stimulators (additive hypotension)
Severe hypotension (systolic <90 mmHg)
Recent history of stroke or MI (within 6 months)

Side effects

Headache, flushing, dyspepsia (most common — PDE5 inhibition in systemic vasculature)
Visual disturbances (PDE6 inhibition in retina — blue tinge, increased light sensitivity)
Hypotension, dizziness
Priapism (uncommon in paediatric PAH doses)
Sudden hearing loss (rare — class effect; MHRA warning)
Non-arteritic anterior ischaemic optic neuropathy (NAION — rare; stop if sudden vision loss)

Interactions

Nitrates (GTN, isosorbide, amyl nitrite): fatal hypotension — absolute contraindication
Alpha-blockers (tamsulosin, doxazosin): additive hypotension — monitor BP; reduce alpha-blocker dose
Strong CYP3A4 inhibitors (clarithromycin, itraconazole, ritonavir): increase sildenafil AUC — reduce dose
Strong CYP3A4 inducers (rifampicin): reduce sildenafil — increase dose

Monitoring

Blood pressure (hypotension risk — measure before and after each dose initiation/increase)
SpO2 and respiratory status (PPHN context — response assessment)
Echocardiogram (pulmonary artery pressure assessment at 3 months and annually in PAH)
Visual acuity and colour vision (annual ophthalmological review in chronic PAH use)
Hepatic and renal function (dose adjustment)

Reference: BNF for Children 2024; NICE TA564; MHRA Drug Safety Update 2014 (paediatric PAH mortality); Steinhorn et al. J Pediatr 2009 (PPHN). Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways