The adverse drug reactions that occurred more frequently on bosentan than on placebo (≥ 3% of bosentan-treated patients, with ≥ 2% difference) were headache (15.8% vs 12.8%), flushing (6.6% vs 1.7%), abnormal hepatic function (5.9% vs 2.1%), leg oedema (4.7% vs 1.4%), and anaemia (3.4% vs 1.0%), all of which were dose related.