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Phosphodiesterase-5 (PDE5) inhibitor Pregnancy: Not for use in women for ED indication. PAH: limited data — specialist use only.

Sildenafil

Brand names: Viagra, Revatio (PAH)

Adult dose

Dose: Erectile dysfunction: 50 mg 30–60 min before intercourse; PAH: 20 mg three times daily
Route: Oral
Frequency: ED: as needed (max once daily); PAH: three times daily
Max: 100 mg per dose (ED); 20 mg TDS (PAH)
ED: start 50 mg, range 25–100 mg, 30–60 minutes before sexual activity. PAH (Revatio): 20 mg three times daily (with or without food). Does NOT work without sexual stimulation.

Paediatric dose

Route: Oral
Frequency: Specific to indication
Max: Not licensed for ED in children. PAH (Revatio): weight-based
Concentration: 10 mg/ml
PAH (paediatric — Revatio): 1 mg/kg TDS (max 20 mg TDS). Paediatric PAH: licensed from birth (oral solution 10 mg/mL). Note: higher doses (2 mg/kg TDS) associated with increased mortality in children (Sildenafil STARTS-2 trial) — avoid.

Dose adjustments

Renal

Start at 25 mg for severe renal impairment (eGFR <30).

Hepatic

Start at 25 mg for hepatic impairment; increased bioavailability.

Clinical pearls

  • Nitrates contraindicated: do not give nitrates for chest pain within 24 hours of sildenafil
  • Priapism: if erection >4 hours — emergency — aspiration and intracavernosal phenylephrine
  • Onset: 30–60 minutes; food (especially high fat) delays absorption
  • NAION (non-arteritic ischaemic optic neuropathy) risk — stop if sudden visual loss
  • PAH dose: Revatio 20 mg TDS (not Viagra dose)

Contraindications

  • Nitrates (GTN, isosorbide) in any form — severe hypotension (contraindicated together)
  • Recent stroke or MI
  • Severe heart failure
  • Hypotension (BP <90/50 mmHg)
  • Non-arteritic anterior ischaemic optic neuropathy (NAION) history

Side effects

  • Headache and flushing
  • Dyspepsia
  • Nasal congestion
  • Visual disturbances (blue tinge, increased brightness — transient)
  • Hypotension (with nitrates or antihypertensives)
  • Priapism (sustained erection >4 hours — emergency)
  • Sudden hearing loss (rare)

Interactions

  • Nitrates — ABSOLUTE CONTRAINDICATION (severe hypotension)
  • Alpha-blockers (doxazosin, tamsulosin) — additive hypotension
  • CYP3A4 inhibitors (ritonavir, ketoconazole) — increased sildenafil levels (reduce dose)
  • Ritonavir — max 25 mg sildenafil every 48 hours

Monitoring

  • Blood pressure
  • Priapism awareness
  • Visual changes
  • Cardiac symptoms

Reference: BNFc; BNF; NICE NG215 Erectile Dysfunction; ESC PAH Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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