Embodiments include a system including a sealed prefilled drug-reservoir. The drug-reservoir may include a unit dosage of treprostinil in a sterile fluid composition. The composition may not include an antimicrobial preservative. The treprostinil may be present at a dosage of between 0.1 mg/mL and 25 mg/mL. In addition, the treprostinil may be treprostinil sodium Furthermore, the composition may include sodium chloride. The composition may also include a sodium ion from sodium chloride in a concentration from 3000 to 4500 ppm. The composition may not include metacresol.