Combined use of ursodeoxycholic acid and bosentan prevents liver toxicity caused by endothelin receptor antagonist bosentan monotherapy: two case reports

INTRODUCTION Pulmonary arterial hypertension is a fatal disease characterized by progressive remodeling of the pulmonary arteries and an increase in pulmonary vascular resistance. Up to 50% of patients with systemic sclerosis have pulmonary arterial hypertension, which significantly affects the prognosis. The endothelin receptor antagonist bosentan is used for the treatment of pulmonary arterial hypertension and shows a great beneficial effect. However, the most frequent side effect of bosentan is liver toxicity, which often requires dose reduction and discontinuation. CASE PRESENTATION We report two cases (a 64-year-old Japanese woman and a 69-year old Japanese woman) of systemic sclerosis, both with severe Raynaud's phenomenon and pulmonary arterial hypertension. Both patients had initially received bosentan monotherapy, which caused liver toxicity as indicated by increased levels of alanine aminotransferase, alkaline phosphatase, and gamma-glutamyltransferase. After dose reduction or discontinuation of bosentan, these liver function abnormalities were normalized and the patients subsequently received retreatment with a combination of bosentan and ursodeoxycholic acid. The results of liver function tests did not show any abnormalities after this combination therapy. CONCLUSIONS These reports suggest the usefulness of ursodeoxycholic acid for preventing liver toxicity caused by bosentan. Thus, the addition of ursodeoxycholic acid to the treatment protocol is expected to be useful when liver toxicity emerges as a side effect of bosentan.