Bosentan Dosing in Newborns
For newborns weighing less than 10 kg, start bosentan at 1 mg/kg twice daily orally (half the maintenance dose of 2 mg/kg twice daily). 1
Dosing Algorithm
The American Heart Association and American Thoracic Society pediatric pulmonary hypertension guidelines provide clear weight-based dosing 1:
- Weight <10 kg: Start at 1 mg/kg twice daily, then increase to maintenance dose of 2 mg/kg twice daily
- Weight 10-20 kg: Start at 15.625 mg twice daily, increase to 31.25 mg twice daily
- Weight 20-40 kg: Start at 31.25 mg twice daily, increase to 62.5 mg twice daily
- Weight >40 kg: Start at 62.5 mg twice daily, increase to 125 mg twice daily
Always begin with half the maintenance dose and uptitrate to minimize adverse effects while establishing therapeutic levels.
Critical Considerations for Neonatal Use
Absorption Challenges
Bosentan absorption in critically ill neonates is problematic. A randomized controlled trial in persistent pulmonary hypertension of the newborn (PPHN) demonstrated that blood concentrations were low and variable on day 1, only achieving steady state by day 5 2. This delayed absorption may explain why the trial showed no improvement in oxygenation or clinical outcomes despite good tolerability.
Safety Monitoring Requirements
- Monthly liver function tests (LFTs) are mandatory due to hepatotoxicity risk, though AST/ALT elevation incidence is lower in children than adults 1
- Monitor for fluid retention and edema (more frequent in neonates) 2
- Anemia occurred more frequently in the bosentan group in neonatal trials 2
- Monthly pregnancy testing and two forms of birth control required for females of childbearing potential due to teratogenicity 1
Clinical Efficacy Evidence
Mixed Results in Neonates
The evidence for bosentan efficacy in newborns is conflicting:
- PPHN trial (2016): Bosentan as adjunctive therapy to inhaled nitric oxide showed no improvement in oxygenation, time to weaning from iNO, or mechanical ventilation 2
- CDH-associated PH (2025): In 50 neonates with congenital diaphragmatic hernia, bosentan at 2 mg/kg/day showed 54% response rate at 1 week with improved pulmonary hypertension severity on echocardiography and reduced need for ECMO 3
Common Pitfalls
- Delayed therapeutic effect: Don't expect immediate response; steady-state concentrations take up to 5 days in critically ill neonates
- Drug interactions: Bosentan interacts with sildenafil—adjust dosing if combining therapies 1
- Route dependency: Nasogastric administration in critically ill neonates may have unpredictable absorption 2
Practical Implementation
Given the delayed absorption and variable pharmacokinetics in neonates, bosentan should be considered early in the treatment course rather than as rescue therapy. The 2 mg/kg twice daily dose (starting at 1 mg/kg twice daily) is well-tolerated and does not adversely affect systemic blood pressure 2, making it a reasonable adjunctive therapy despite mixed efficacy data.
The guideline recommendation carries Class I, Level of Evidence B 1, making it the strongest available evidence for dosing, though clinicians should be aware that neonatal-specific efficacy remains uncertain and highly dependent on the underlying condition.