[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)](https://durgical.com/en/pharmacology/classes/pulmonary-arterial-hypertension-drugs/) › Bosentan

# 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.

Updated Nov 1, 2026

## Quick facts

**Group**
[Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)](https://durgical.com/en/pharmacology/classes/pulmonary-arterial-hypertension-drugs/)

**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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Endothelin receptors type A and type B**Bosentan

ⓘ The figure shows bosentan bound to the human endothelin receptor type B (crystal structure); bosentan blocks type A receptors as well.

**Target in 3D:** Endothelin receptors type A and type B. PDB structure 5XPR (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/5XPR) · Drag to rotate · pinch to zoom

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 →](https://durgical.com/en/conditions/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

### Serious (rare, important)

- Hepatotoxicity: raised transaminases and liver failure
- Birth defects and fetal death if used in pregnancy
- Pulmonary oedema in pulmonary veno-occlusive disease
- Severe hypersensitivity, including DRESS and anaphylaxis

## 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

## Memory aid

BOSentan is the liver's BOSS problem: monthly liver tests, no pregnancy, and it bosses the CYP enzymes (induces 3A and 2C9).

## 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).

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/bosentan/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**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.

## Connections

## Related drugs 4

- [Ambrisentan](https://durgical.com/en/pharmacology/ambrisentan/)
- [Sildenafil](https://durgical.com/en/pharmacology/sildenafil/)
- [Ciclosporin](https://durgical.com/en/pharmacology/ciclosporin/)
- [Glibenclamide](https://durgical.com/en/pharmacology/glibenclamide/)

## Related conditions 1

- [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/)

[← Back to the class: Pulmonary arterial hypertension drugs (endothelin receptor antagonists and prostacyclins)](https://durgical.com/en/pharmacology/classes/pulmonary-arterial-hypertension-drugs/)

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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=39b2a85f-4322-42d4-b420-1b1d52569143) (DailyMed (U.S. National Library of Medicine), 2025); [Bosentan: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a605001.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [RCSB PDB - 5XPR: Human endothelin receptor type-B in complex with antagonist bosentan](https://www.rcsb.org/structure/5XPR) (RCSB Protein Data Bank, 2017).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/bosentan/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/bosentan/