Patients who have been on a stable dose of 125 mg twice daily (bid) of bosentan or any stable dose of sildenafil for at least three months prior to study start were randomized to either treprostinil inhalation solution or matching placebo.
Administration of study medication was performed by inhalation with the OPTINEB™ ultrasonic nebulizer.
The proposed dosing regimen was four times daily-upon awakening, at midday, evening (dinner time) and bedtime.
After a patient has completed the twelve-week study period, they were given the option of enrolling into an open-label extension study.
