In children under 5 years of age with severe pulmonary hypertension, sildenafil therapy resulted in prolonged hemodynamic improvements without adverse effects. Sildenafil attenuated rebound pulmonary hypertension after withdrawal of inhaled nitric oxide.
Humpl, T., Reyes, J. T., Erickson, S., Armano, R., Holtby, H., & Adatia, I. (2011). Sildenafil therapy for neonatal and childhood pulmonary hypertensive vascular disease. Cardiology in the Young, 21(2), 187-193. https://doi.org/10.1017/S1047951110001745 (Original work published 2011)