This single center, open label, randomized, two-period, two-sequence cross-over study is designed to evaluate the relative bioavailability of a treprostinil diethanolamine 1 mg tablet in reference to treprostinil diethanolamine 1 mg oral solution (administered as four 0.25 mg doses every 2 hours for a 1 mg total dose) in twenty-four healthy volunteers. Other secondary outcomes of interest include assessment of pharmacokinetic parameters of treprostinil diethanolamine 1 mg tablets and a treprostinil diethanolamine 1 mg oral solution administered as four doses (0.25 mg every 2 hours for a 1 mg total dose) and evaluation of the safety and tolerability of each treatment regimen.