Bosentan
Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)
Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)Pregnancy: contraindicated
Contraindicated: animal studies show birth defects and fetal death; pregnancy is excluded before treatment and effective contraception continues until a month after stopping.
An oral endothelin receptor blocker for pulmonary arterial hypertension; it can harm the liver and the fetus, so it needs close monitoring.
Quick facts
- Group
- Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)
- Target
- Endothelin receptors type A and type B
- Used for
- Pulmonary arterial hypertension
- Key effects
- Respiratory tract infections · Anaemia
- Monitor
- Liver transaminases · Pregnancy test before starting
- ATC
- C02KX01
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows bosentan bound to the human endothelin receptor type B (crystal structure); bosentan blocks type A receptors as well.
Bosentan is a competitive antagonist of both endothelin receptors, with slightly higher affinity for ETA than ETB. Endothelin-1 is raised in the blood and lungs of patients with pulmonary arterial hypertension; through ETA it constricts pulmonary arteries and drives smooth-muscle growth. Blocking it lowers pulmonary vascular resistance and improves exercise capacity. Bosentan also induces the liver enzymes CYP3A and CYP2C9, which explains many of its interactions.
- Endothelin-1 is overproduced in the lungs in PAH
- Bosentan blocks ETA and ETB receptors on the vessel wall
- Pulmonary arteries constrict and proliferate less
- Pulmonary vascular resistance falls; exercise improves
Indications
- Pulmonary arterial hypertension (WHO group 1) in adults, to improve exercise ability and reduce clinical worsening Pulmonary hypertension and cor pulmonale →
- Idiopathic or congenital pulmonary arterial hypertension in children, to improve pulmonary vascular resistance
Adverse effects
Common
- Respiratory tract infections
- Anaemia (falling haemoglobin)
- Fluid retention and oedema
- Headache and flushing
- Lower sperm counts
Contraindications
- Pregnancy
- Use with ciclosporin
- Use with glibenclamide (glyburide)
- Hypersensitivity to bosentan
Key interactions
- Ciclosporin
- Markedly higher bosentan levels; contraindicated
- Glibenclamide (glyburide)
- Higher risk of liver enzyme elevation; contraindicated
- Hormonal contraceptives (oral, injectable, patch, implant)
- Bosentan lowers their levels; they cannot be relied on alone
- Sildenafil
- Sildenafil levels fall and bosentan levels rise
- Strong CYP3A and CYP2C9 inhibitors (ketoconazole, ritonavir)
- Higher bosentan exposure
What is monitored
- Liver transaminases (ALT, AST) before treatment and monthly; bilirubin if they rise
- Pregnancy test before starting in females who could become pregnant, and promptly if a period is late or pregnancy is suspected
- Haemoglobin after the first and third months, then periodically
- Weight and oedema for fluid retention
Administration and safety
- Oral film-coated or dispersible tablets; distributed through a restricted programme in some countries because of liver and fetal risk
- Hormonal contraceptives alone are not reliable: additional contraceptive methods are needed during treatment and for a month after
Pregnancy and breastfeeding
Contraindicated: animal studies show birth defects and fetal death; pregnancy is excluded before treatment and effective contraception continues until a month after stopping.
Nursing care
- Check liver test results before each refill and watch for jaundice, dark urine, nausea or right upper abdominal pain
- Confirm a negative pregnancy test and contraception counselling
- Weigh the patient and look for ankle swelling and worsening breathlessness
- Review the medication list for ciclosporin, glibenclamide and hormonal contraceptives
Pharmacokinetics
- Absorption
- Oral; food does not change absorption
- Distribution
- Very highly bound to albumin
- Metabolism
- Liver, by CYP2C9 and CYP3A; it induces these enzymes and lowers its own levels over the first days
- Elimination
- Biliary, as metabolites
- Half-life
- About 5 hours in healthy adults
Test yourself
Think of the answer, then tap the question to see it.
Which two laboratory checks are essential during bosentan treatment?
Liver transaminases (monthly) and, in females who could become pregnant, pregnancy tests; haemoglobin is also followed.
Why is a combined oral contraceptive not enough with bosentan?
Bosentan induces CYP3A and lowers contraceptive hormone levels.
Which immunosuppressant is contraindicated with bosentan, and why?
Ciclosporin: it markedly raises bosentan concentrations.
Which endothelin receptors does bosentan block?
Both ETA and ETB (dual antagonist).
Connections
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - BOSENTAN tablet, film coated (DailyMed (U.S. National Library of Medicine), 2025); Bosentan: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); RCSB PDB - 5XPR: Human endothelin receptor type-B in complex with antagonist bosentan (RCSB Protein Data Bank, 2017).
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Representative model, for educational purposes only.