692 GB Kim •Pulmonary hypertension in infants with bronchopulmonary dysplasia patients with PH by decreasing RV dilatation and by improving RV function and left ventricular blood filling without significant negative effect on systemic pressure40, 41). Long-term randomized controlled studies have not been conducted in the patients with BPD using bosentan; however, other studies have shown that bosentan improved PH and functional status in daily life6, 42). The recommended starting dose of bosentan is 1.5 mg/kg/L every 12 h. If the patient shows no hepatic dysfunction after 2 weeks, the dose may be increased up to 3 mg/kg/d every 12 h. During the treatment, regular liver function tests must be conducted because bosentan is known to be hepatotoxic43). Combination therapy, which involves the simultaneous prescription of more than one selective PH drug, has become the standard treatment in many centers. Several case series have suggested that various drug combinations appear to be safe and effective10); however, long-term safety and efficacy have not been evaluated in the pediatric population. The advancements in pharmaceutical research will lead to the development of new selective pulmonary vasodilators in the near future. Discontinuance of medications used for treating PH in the BPD patients should be determined only after serial echocardiography. If 2 consecutive serial echocardiographic examinations reveal normal or near-normal findings, weaning and discontinuance of medication for PH may be considered12). Conclusions Because of an increase in the number of preterm infants and a decrease in the gestational age at birth, more patients are showing significant BPD and secondary PH. PH contributes significantly to the high morbidity and mortality in the BPD patients. 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