Bosentan

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Bosentan (BOZENTAN) is a dual endothelin receptor antagonist important in the treatment of pulmonary artery hypertension (PAH). It is licensed in the United States, the European Union and other countries by Actelion Pharmaceuticals for the management of PAH under the trade name Tracleer®.

Indications
Bosentan is used to treat pulmonary hypertension by blocking the action of endothelin molecules that would otherwise promote narrowing of the blood vessels and lead to high blood pressure.

Mechanism of action
Bosentan works by competitively and specifically binding to ETA and ETB receptor sites in the endothelium and vascular smooth muscle. In so binding, it prevents the neurohormone endothelin-1 (ET-1) from binding to these same receptor sites and triggering vasoconstriction. Bosentan shows somewhat higher affinity for ETA receptors than ETB receptors.

Dosage
This medication is normally given in pill form. Administration of bosentan is normally initiated at a dosage of 62.5 mg twice daily for a period of four weeks. If no adverse drug reactions are observed, the dosage is raised to a maintenance level of 125 mg twice daily. Studies have not shown sufficient benefit from higher doses to counter the increased risk of liver damage.

Pharmacokinetic Data

 * tcmax = 3 to 5 hours after oral dosing (time elapsed before maximal concentration in the blood plasma is reached)

Warnings and precautions
Bosentan can cause liver damage, so patients taking it should have their liver function tested monthly while on the medication.

Bosentan can cause major birth defects, so women of childbearing-age must be tested for pregnancy prior to taking this medication, and use non-hormonal means of contraception (i.e. birth control pills cannot be relied upon in this situation).