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Selective Endothelin-A Receptor Antagonist — Pulmonary Arterial Hypertension Pregnancy: Contraindicated — teratogenic; mandatory pregnancy prevention

Ambrisentan

Brand names: Volibris

Adult dose

Dose: 5 mg once daily; may increase to 10 mg once daily after 4 weeks if tolerated
Route: Oral
Frequency: Once daily
Max: 10 mg/day
ET-A selective (unlike bosentan which blocks ET-A and ET-B). AMBITION trial: upfront combination ambrisentan + tadalafil superior to monotherapy. Pregnancy prevention programme mandatory. Less hepatotoxic than bosentan — monthly LFT monitoring not mandated but recommend at baseline and periodically.

Paediatric dose

Route:
Seek specialist opinion — not licensed in paediatrics

Dose adjustments

Renal

No dose adjustment required

Hepatic

Contraindicated in moderate-severe hepatic impairment

Clinical pearls

  • AMBITION trial (2015): ambrisentan + tadalafil upfront combination therapy reduced clinical failure events by 50% vs monotherapy — now the standard approach for newly diagnosed PAH (WHO FC II–III)
  • ET-A selectivity: theoretical advantage of preserving ET-B-mediated endogenous prostacyclin release and NO production — less fluid retention than dual ERA? Clinically: peripheral oedema still common
  • Does NOT induce CYP450 — no interaction with warfarin or oral contraceptives (advantage over bosentan)
  • Contraindicated in IPF — ARTEMIS-IPF trial: increased mortality in IPF patients

Contraindications

  • Pregnancy
  • Women of childbearing potential without reliable contraception
  • Idiopathic pulmonary fibrosis
  • Moderate-severe hepatic impairment

Side effects

  • Peripheral oedema (very common — fluid retention)
  • Nasal congestion
  • Sinusitis
  • Flushing
  • Headache
  • Palpitations
  • Anaemia (less than bosentan)
  • Hepatotoxicity (rare — less than bosentan)

Interactions

  • Cyclosporine — increases ambrisentan levels (reduce dose to 5 mg max)
  • Strong CYP3A4/P-gp inhibitors — increase levels
  • Hormonal contraceptives — ambrisentan does not reduce efficacy (unlike bosentan — major advantage)
  • Warfarin — no significant interaction

Monitoring

  • LFTs at baseline and if symptoms suggest hepatotoxicity
  • Haemoglobin at baseline and periodically
  • Pregnancy test monthly
  • Fluid balance/weight (oedema)
  • 6MWD and RHC response

Reference: BNFc; BNF 90; AMBITION Trial 2015; ARIES-1/2 Trials; NICE TA459; ESC/ERS PAH Guidelines 2022. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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