Bosentan

How it works

It antagonises endothelin-1 at both ETA and ETB receptors, reducing endothelin-mediated pulmonary vasoconstriction and vascular proliferation.

Prescribing in practice

• It is hepatotoxic and teratogenic; liver enzymes must be monitored and effective contraception is required, with reliable pregnancy testing before and during treatment.
• It reduces the efficacy of hormonal contraceptives, so hormonal methods alone must not be relied upon for contraception.
• It is a CYP inducer with numerous interactions, including with ciclosporin and glibenclamide, which are contraindicated.

Monitoring

Monitor liver transaminases regularly throughout treatment, along with haemoglobin and pregnancy status in those who can become pregnant.

Counselling the patient

• Use reliable non-hormonal or additional contraception and avoid pregnancy while taking this medicine.
• Attend for regular liver blood tests and report nausea, vomiting, abdominal pain or yellowing of the skin or eyes.

Evidence & guidelines

Bosentan's efficacy in pulmonary arterial hypertension was established in the BREATHE trials, and it is recommended in specialist guidance.