The mean AUC (CV%) values of bosentan in paediatric patients treated with 31.25, 62.5 or 125 mg b.i.d. were 3496 (49), 5428 (79), and 6124 (27) ng·h/ml, respectively, and were lower than the value of 8149 (47) ng·h/ml observed in adult patients with pulmonary arterial hypertension receiving 125 mg b.i.d.