De bivirkninger, som optrådte hyppigere hos patienter, der blev behandlet med bosentan, end hos dem, der fik placebo (≥ 3% af patienter behandlet med bosentan med ≥ 2% forskel), var hovedpine (15, 8% versus 12, 8%), rødme (6, 6% versus 1, 7%), anormal leverfunktion (5, 9% versus 2, 1%), ødem i ben (4, 7% versus 1, 4%) og anæmi (3, 4% versus 1, 0%), som alle var dosisrelaterede.
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.