Q: Can sildenafil be given as IV in the treatment of pulmonary hypertension?

Answer:  Yes

IV sildenafil as a bolus in dose from 2.5 mg to 10 mg (tid) has been shown as a potent dilator in pulmonary hypertension. At least one study in children has shown it to be as effective as iNO.

Reference:

Ingram Schulze-Neick, MD; Paulina Hartenstein, BSc; Jia Li, MD; Brigitte Stiller, MD; Nicole Nagdyman, MD; Michael Hübler, MD; Ghazwan Butrous, MD; Andy Petros, MD; Peter Lange, MD; Andrew N. Redington, MD - Intravenous Sildenafil Is a Potent Pulmonary Vasodilator in Children With Congenital Heart Disease -  Circulation. 2003; 108: II-167-II-173